Climate Change and...
- Climate Variability
- Climate Models
Effects of Climate Change
Carbon Management and Mitigation Strategies
Anderson, R.G., Canadell, J.G., Randerson, J.T., Jackson, R.B., Hungate, B.A., Baldocchi, D.D., Ban-Weiss, G.A., Bonan, G.B., Caldeira. K., Cao, L., Diffenbaugh, N.S., Gurney, K.R., Kueppers, L.M., Law, B.E., Luyssaert, S., and O'Halloran, T.L. (2010). Biophysical considerations in forestry for climate protection. Front Ecol Environ 9(3): 174–182, doi:10.1890/09017
ABSTRACT: Forestry – including afforestation (the planting of trees on land where they have not recently existed), reforestation,avoided deforestation, and forest management – can lead to increased sequestration of atmospheric carbon dioxide and has therefore been proposed as a strategy to mitigate climate change. However, forestry also influences land-surface properties, including albedo (the fraction of incident sunlight reflected back to space), surface roughness, and evapotranspiration, all of which affect the amount and forms of energy transfer to the atmosphere. In some circumstances, these biophysical feedbacks can result in local climate warming, thereby counteracting the effects of carbon sequestration on global mean temperature and reducing or eliminating the net value of climate-change mitigation projects. Here, we review published and emerging research that suggests ways in which forestry projects can counteract the consequences associated with biophysical interactions, and highlight knowledge gaps in managing forests for climate protection. We also outline several ways in which biophysical effects can be incorporated into frameworks that use the maintenance of forests as a climate protection strategy.
J. M. Antle, S. M. Capalbo, K. Paustian, M. K.Ali (2007). Estimating the economic potential for agricultural soil carbon sequestration in the Central United States using an aggregate econometric-process simulation model. Climatic Change V80 (1): 145-171
ABSTRACT: The purpose of this paper is to develop and apply a new method to assess economic potential for agricultural greenhouse gas mitigation. This method uses secondary economic data and conventional econometric production models, combined with estimates of soil carbon stocks derived from biophysical simulation models such as Century, to construct economic simulation models that estimate economic potential for carbon sequestration. Using this method, simulations for the central United States show that reduction in fallow and conservation tillage adoption in the wheat-pasture system could generate up to about 1.7 million MgC/yr, whereas increased adoption of conservation tillage in the corn–soy–feed system could generate up to about 6.2 million MgC/yr at a price of $200/MgC. About half of this potential could be achieved at relatively low carbon prices (in the range of $50 per ton). The model used in this analysis produced estimates of economic potential for soil carbon sequestration potential similar to results produced by much more data-intensive, field-scale models, suggesting that this simpler, aggregate modeling approach can produce credible estimates of soil carbon sequestration potential. Carbon rates were found to vary substantially over the region. Using average carbon rates for the region, the model produced carbon sequestration estimates within about 10% of those based on county-specific carbon rates, suggesting that effects of spatial heterogeneity in carbon rates may average out over a large region such as the central United States. However, the average carbon rates produced large prediction errors for individual counties, showing that estimates of carbon rates do need to be matched to the spatial scale of analysis. Transaction costs were found to have a potentially important impact on soil carbon supply at low carbon prices, particularly when carbon rates are low, but this effect diminishes as carbon prices increase.
This research was supported in part by the Montana State Agricultural Experiment Station, by the EPA STAR Climate Change program and by the Consortium for the Agricultural Mitigation of Greenhouse Gases. Although the research described in this article has been funded wholly or in part by the United States Environmental Protection Agency through grant R-82874501-0 to Montana State University, it has not been subjected to the Agency’s required peer and policy review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred.
Bedard-Haughn, A., Jongbloed, F., Akkerman, J., Uijl, A., de Jong, E., Yates, T., Pennock, D. (2006). The effects of erosional and management history on soil organic carbon stores in ephemeral wetlands of hummocky agricultural landscapes. Geoderma 135: 296-306
ABSTRACT: Carbon sequestration by agricultural soils has been widely promoted as a means of mitigating greenhouse gas emissions. In many regions agricultural fields are just one component of a complex landscape matrix and understanding the interactions between agricultural fields and other landscape components such as wetlands is crucial for comprehensive, whole-landscape accounting of soil organic carbon (SOC) change. Our objective was to assess the effects of management and erosional history on SOC storage in wetlands of a typical hummocky agricultural landscape in southern Saskatchewan. Wetlands were classed into three land management groups: native wetlands (i.e., within a native landscape), and uncultivated and cultivated wetlands within an agricultural landscape. Detailed topographic surveys were used to develop a digital elevation model of the sites and landform segmentation algorithms were used to delineate the topographic data into landform elements. SOC density to 45 cm was assessed at seven uncultivated wetlands, seven cultivated wetlands, and twelve native wetlands. Mean SOC density decreased from 175.1 mg ha−1 to 30 cm (equivalent mass depth) for the native wetlands to 168.6 mg ha−1 for the uncultivated wetlands and 87.2 mg ha−1 for the cultivated wetlands in the agricultural field. The SOC density of sediment depositional fans in the uncultivated wetlands is high but the total SOC stored in the fans is low due to their small area. The uncultivated wetlands occupy only 11% of the site but account for approximately 23% of SOC stores. Re-establishing permanent vegetation in the cultivated wetlands could provide maximum C sequestration with minimum energy inputs and a minimum loss of productive acreage but the overall consequences for the gas emissions would have to be carefully assessed.
ABSTRACT: Mitigating or slowing an increase in atmospheric carbon dioxide concentration ([CO2 ]) has been the focus of international efforts, most apparent with the development of the Kyoto Protocol. Sequestration of carbon (C) in agricultural soils is being advocated as a method to assist in meeting the demands of an international C credit system. The conversion of conventionally tilled agricultural lands to no till is widely accepted as having a large-scale sequestration potential. In this study, C flux measurements over a no-till corn/soybean agricultural ecosystem over 6 years were coupled with estimates of C release associated with agricultural practices to assess the net biome productivity (NBP) of this no-till ecosystem. Estimates of NBP were also calculated for the conventionally tilled corn/soybean ecosystem assuming net ecosystem exchange is C neutral. These measurements were scaled to the US as a whole to determine the sequestration potential of corn/soybean ecosystems, under current practices where 10% of agricultural land devoted to this ecosystem is no-tilled and under a hypothetical scenario where 100% of the land is not tilled. The estimates of this analysis show that current corn/soybean agriculture in the US releases ~7.2 Tg C annually, with no-till sequestering ~2.2 Tg and conventional-till releasing ~9.4 Tg. The complete conversion of land area to no till might result in 21.7 Tg C sequestered annually, representing a net C flux difference of ~29 Tg C. These results demonstrate that large-scale conversion to no-till practices, at least for the corn/soybean ecosystem, could potentially offset ca. 2% of annual US carbon emissions.
Bernoux, M., Cerri, C. C., Volkoff, B., Carvalho, M. Da Conceição S., Feller, C., Cerri, C. E. P., Eschenbrenner, V., Piccolo, M. De C., Feigl, B. (2005). Greenhouse gas fluxes and carbon storage from soil: The Brazilian inventory. Cahiers Agricultures 14 (1): 96-100
ABSTRACT: Rising levels of atmospheric CO2 have focused attention on potential CO2 emissions from terrestrial ecosystems of the world, notably from soils and biomass. The world’s mineral soils represent a large reservoir of C of about 1500 Pg C. Under the United Nations Framework Convention on Climate Change (UNFCCC) each country is required to develop, update and publish a national inventories of anthropogenic emissions (implementation of the National Communications), as well as to compile the inventories by comparable methodologies. For the last point, guidelines were developed and published as IPCC Guidelines for National Greenhouse Gas Inventories. Also, the land use, land-use changes and forestry (LULUCF) sector should be included in the national inventories. The CO2 fluxes from soils are discussed in chapter 5 for agricultural soils under the category 5D: CO2 emissions and removals from soils. These emissions are calculated from three subcategories : i) net changes in C storage in mineral soils; ii) emissions from organic soils; and iii) emissions from liming of agricultural soils. In a first step the soil organic carbon stocks up to a depth of 30 cm were estimated for Brazil based on a map of different soil-vegetation associations combined with results from a soil database. The soil-vegetation associations map was derived by intersecting soil and vegetation maps. The original soil and vegetation classification were reduced to 6 soil and 15 vegetation categories. Because this data represents sites with native vegetation in the absence of significant disturbances, it constitutes a valuable baseline for evaluating the effect of land-use change on soil C stocks for Brazil. Overall, about 36 400 million tons of carbon would be stored in the 0-30 cm soil layer under native conditions. The Brazilian Amazon region would account for 22,000 million tons. The CO2 emission from mineral soils following land-cover change in Brazil for the period 1975-1995 was estimated by Bernoux et al. who showed that the annual fluxes for Brazil indicate a net emission of CO2 to the atmosphere of 46.4 million tons of CO2 for the period 1975-1995. Intermediary calculation used to derive these annual fluxes estimated that 34 400 million tons of carbon were stored in the Brazilian soil for the year 1995. The annual CO2 emission for Brazil from liming varied from 4.9 to 9.4 million tons of CO2 per year with a mean annual CO2 emission of about 7.2 million tons. The South, Southeast and Center region accounted for a least 92% of total emission. Finally it could be calculated that the total CO2 fluxes from soils reached around 51.9 million tons of CO2 per year for the period 1975-1995.
ABSTRACT: The human perturbation of the carbon cycle via the release of fossil CO2 and land use change is now well documented and agreed to be the principal cause of climate change. We address three fundamental research areas that require major development if we were to provide policy relevant knowledge for managing the carbon-climate system over the next few decades. The three research areas are: (i) carbon observations and multiple constraint data assimilation; (ii) vulnerability of the carbon-climate system; and (iii) carbon sequestration and sustainable development.
Cerri, C. E. P., Sparovek, G., Bernoux, M., Easterling, W. E., Melillo, J. M., Cerri, C. C. (2007). Tropical agriculture and global warming: impacts and mitigation options. Scientia Agricola 64 (1): 83-99
ABSTRACT: The intensive land use invariably has several negative effects on the environment and crop production if conservative practices are not adopted. Reduction in soil organic matter (SOM) quantity means gas emission (mainly CO2 , CH4 , N2 O) to the atmosphere and increased global warming. Soil sustainability is also affected, since remaining SOM quality changes. Alterations can be verified, for example, by soil desegregation and changes in structure. The consequences are erosion, reduction in nutrient availability for the plants and lower water retention capacity. These and other factors reflect negatively on crop productivity and sustainability of the soil -plant-atmosphere system. Conversely, adoption of "best management practices", such as conservation tillage, can partly reverse the process - they are aimed at increasing the input of organic matter to the soil and/or decreasing the rates at which soil organic matter decomposes.
ABSTRACT: Biomass crops mitigate carbon emissions by both fossil fuel substitution and sequestration of carbon in the soil. We grewMiscanthus x giganteus for 16 years at a site in southern Ireland to (i) compare methods of propagation, (ii) compare response to fertilizer application and quantify nutrient offtakes, (iii) measure long-term annual biomass yields, (iv) estimate carbon sequestration to the soil and (v) quantify the carbon mitigation by the crop. There was no significant difference in the yield between plants established from rhizome cuttings or by micro-propagation. Annual off-takes of N and P were easily met by soil reserves, but soil K reserves were low in unfertilized plots. Potassium deficiency was associated with lower harvestable yield. Yields increased for 5 years following establishment but after 10 years showed some decline which could not be accounted for by the climate driven growth model MISCANMOD. Measured yields were normalized to estimate both autumn (at first frost) and spring harvests (15 March of the subsequent year). Average autumn and spring yields over the 15 harvest years were 13.4±1.1 and 9.0±0.7 t DW ha−1 yr−1 respectively. Below ground biomass in February 2002 was 20.6±4.6 t DW ha−1 .Miscanthus derived soil organic carbon sequestration detected by a change in13 C signal was 8.9±2.4 t C ha−1 over 15 years. We estimate total carbon mitigation by this crop over 15 years ranged from 5.2 to 7.2 t C ha−1 yr−1 depending on the harvest time.
Dalal, R.C., Allen, D.E., Livesley, S.J., Richards, G. (2007). Magnitude and biophysical regulators of methane emission and consumption in the Australian agricultural, forest, and submerged landscapes: a review. Plant And SoilPlant Soil 309 (1-2): 43-76
ABSTRACT: Increases in the concentrations of atmospheric greenhouse gases, carbon dioxide (CO2 ), methane (CH4 ), nitrous oxide (N2 O) due to human activities are associated with global climate change. CO2 concentration in the atmosphere has increased by 33% (to 380 ppm) since 1750 ad, whilst CH4 concentration has increased by 75% (to 1,750 ppb), and as the global warming potential (GWP) of CH4 is 25 fold greater than CO2 it represents about 20% of the global warming effect. The purpose of this review is to: (a) address recent findings regarding biophysical factors governing production and consumption of CH4 , (b) identify the current level of knowledge regarding the main sources and sinks of CH4 in Australia, and (c) identify CH4 mitigation options and their potential application in Australian ecosystems. Almost one-third of CH4 emissions are from natural sources such as wetlands and lake sediments, which is poorly documented in Australia. For Australia, the major anthropogenic sources of CH4 emissions include energy production from fossil fuels (~24%), enteric fermentation in the guts of ruminant animals (~59%), landfills, animal wastes and domestic sewage (~15%), and biomass burning (~5%), with minor contributions from manure management (1.7%), land use, land-use change and forestry (1.6%), and rice cultivation (0.2%). A significant sink exists for CH4 (~6%) in aerobic soils, including agricultural and forestry soils, and potentially large areas of arid soils, however, due to limited information available in Australia, it is not accounted for in the Australian National Greenhouse Gas Inventory. CH4 emission rates from submerged soils vary greatly, but mean values ≤10 mgm−2 h−1 are common. Landfill sites may emit CH4 at one to three orders of magnitude greater than submerged soils. CH4 consumption rates in non-flooded, aerobic agricultural, pastoral and forest soils also vary greatly, but mean values are restricted to ≤100μg m−2 h−1 , and generally greatest in forest soils and least in agricultural soils, and decrease from temperate to tropical regions. Mitigation options for soil CH4 production primarily relate to enhancing soil oxygen diffusion through water management, land use change, minimised compaction and soil fertility management. Improved management of animal manure could include biogas capture for energy production or arable composting as opposed to open stockpiling or pond storage. Balanced fertiliser use may increase soil CH4 uptake, reduce soil N2 O emissions whilst improving nutrient and water use efficiency, with a positive net greenhouse gas (CO2 -e) effect. Similarly, the conversion of agricultural land to pasture, and pastoral land to forestry should increase soil CH4 sink. Conservation of native forests and afforestation of degraded agricultural land would effectively mitigate CH4 emissions by maintaining and enhancing CH4 consumption in these soils, but also by reducing N2 O emissions and increasing C sequestration. The overall impact of climate change on methanogenesis and methanotrophy is poorly understood in Australia, with a lack of data highlighting the need for long-term research and process understanding in this area. For policy addressing land-based greenhouse gas mitigation, all three major greenhouse gases (CO2 , CH4 and N2 O) should be monitored simultaneously, combined with improved understanding at process-level.
ABSTRACT: Increasing the accumulation of organic carbon (C) in agricultural soils provides one means to reduce atmospheric carbon dioxide (CO2 ) concentrations, but detection of the relatively small changes in soil organic C is complicated by spatial variability. Soil organic C variation was assessed at various scales within a small (40 ha; 98 ac), mixed-use watershed in central Pennsylvania to determine sampling requirement for possible C credit programs. Composite soil samples (0 to 5 cm; 0 to 2 in deep) were collected on 30-m (98-ft) grid intervals across the watershed and at 10- and 0.6-m (33- and 2-ft) intervals at selected locations, and descriptive- and geo-statistical analysis utilized. Concentrations of soil organic C in pasture and forest soils were approximately two times greater than cultivated fields, where means ranged from 15 to 24 g C kg−1 (1.5 to 2.4 percent) and coefficients of variation were typically 15 to 20 percent. Soil organic C was spatially dependent over a range of approximately 200 m (660 ft) when sampled at 30-m (98-ft) intervals, and high nugget variances indicated spatially-dependent variability over lag distances shorter than 30 m (98ft). However, sampling at 10-m (33 ft) intervals appeared to adequately describe variation. Estimates of sample size requirement showed that, with the observed coefficient variances for individual fields, two- to five-fold increases in sample numbers would be required to verify statistically significant soil organic C changes ≤ 10 percent. Given the large number of samples required to provide representative measurements and the concurrent cost for labor and analysis, participation by farmers in a C credit program could be low if measured verification of soil organic C increases are required. Basing payments on modeled, rather than measured C sequestration rates, should be considered.
ABSTRACT: Management of rangelands can aid in the mitigation of rising atmospheric carbon dioxide concentrations via carbon storage in biomass and soil organic matter, a process termed carbon sequestration. Here we provide a review of current knowledge on the effects of land management practices (grazing, nitrogen inputs, and restoration) and precipitation on carbon sequestration in rangelands. Although there was no statistical relationship between change in soil carbon with longevity of the grazing management practice in native rangelands of the North American Great Plains, the general trend seems to suggest a decrease in carbon sequestration with longevity of the grazing management practice across stocking rates. The relationship of carbon sequestration to mean annual precipitation is negative for both the 0 to 10 cm (0 to 3.9 in) and 0 to 30 cm (0 to 11.8 in) soil depths across stocking rates. The threshold from positive to negative carbon change occurs at approximately 440 mm (17.3 in) of precipitation for the 0 to 10 cm soil depth and at 600 mm (23.6 in) for the 0 to 30 cm soil depth. We acknowledge that largely unexplored is the arena of management-environment interactions needed to increase our understanding of climate-plant-soil-microbial interactions as factors affecting nutrient cycling. Continued refinement of estimates of terrestrial carbon storage in rangelands will assist in the development of greenhouse gas emissions and carbon credit marketing policies, as well as potentially modifying government natural resource conservation programs to emphasize land management practices that increase carbon sequestration.
ABSTRACT: Forestry has an important role to play as a provider of energy from renewable biomass and through the sequestration of carbon in biomass and soil. Forests are also habitats for a large number of species which are important for biodiversity. In some cases, these two roles may conflict. The aim of this study was to model the implications of specific environmental quality objectives on the potential of forestry to reduce net CO2 emissions by addressing interim targets 1 and 2 in the environmental quality objective, sustainable forests for Uppsala County and used this region as a case study. The carbon stock in the biomass, the substitution effect, and the economic consequences associated with six forest management scenarios were considered. The development for the scenarios was simulated at stand level using an empirical model. The results of the study showed that the shortest rotation period was preferable to mitigate net CO2 emissions since it resulted in more biomass that could replace fossil fuel. However, such a strategy might affect sustainable policies negatively. Increasing the extent of mixed stands could be a preferable strategy since it may achieve several objectives.
ABSTRACT: Atmospheric carbon dioxide (CO2 ) has increased from a preindustrial concentration of about 280 ppm to about 367 ppm at present. The increase has closely followed the increase in CO2 emissions from the use of fossil fuels. Global warming caused by increasing amounts of greenhouse gases in the atmosphere is the major environmental challenge for the 21st century. Reducing worldwide emissions of CO2 requires multiple mitigation pathways, including reductions in energy consumption, more efficient use of available energy, the application of renewable energy sources, and sequestration. Sequestration is a major tool for managing carbon emissions. In a majority of cases CO2 is viewed as waste to be disposed; however, with advanced technology, carbon sequestration can become a value-added proposition. There are a number of potential opportunities that render sequestration economically viable. In this study, we review these most economically promising opportunities and pathways of carbon sequestration, including reforestation, best agricultural production, housing and furniture, enhanced oil recovery, coalbed methane (CBM), and CO2 hydrates. Many of these terrestrial and geological sequestration opportunities are expected to provide a direct economic benefit over that obtained by merely reducing the atmospheric CO2 loading. Sequestration opportunities in 11 states of the Southeast and South Central United States are discussed. Among the most promising methods for the region include reforestation and CBM. The annual forest carbon sink in this region is estimated to be 76 Tg C/year, which would amount to an expenditure of $11.1-13.9 billion/year. Best management practices could enhance carbon sequestration by 53.9 Tg C/year, accounting for 9.3% of current total annual regional greenhouse gas emission in the next 20 years. Annual carbon storage in housing, furniture, and other wood products in 1998 was estimated to be 13.9 Tg C in the region. Other sequestration options, including the direct injection of CO2 in deep saline aquifers, mineralization, and biomineralization, are not expected to lead to direct economic gain. More detailed studies are needed for assessing the ultimate changes to the environment and the associated indirect cost savings for carbon sequestration.
Harper, R.J., Beck, A.C., Ritson, P., Hill, M.J., Mitchell, C.D., Barrett, D.J., Smettem, K.R.J., Mann, S.S. (2007). The potential of greenhouse sinks to underwrite improved land management. Ecological Engineering 29 (4): 329-341
ABSTRACT: The current agricultural systems of broad areas of Australia are unsustainable, with large projected increases in salinization, decreases in water quality, wind erosion, and losses of biodiversity. It is well known that these problems can be partially resolved by farmland reforestation; however, a major issue is financing the scale of activity required. The international response to global warming, the United Nations Framework Convention on Climate Change and its Kyoto Protocol, includes provisions that enable greenhouse sinks (sequestration of carbon in soils and vegetation) to be used by parties to fulfil their obligations. The Kyoto Protocol also allows for trading in emission reductions, and this opens the possibility that investment in carbon sinks may help underwrite broader natural resource management objectives. This paper examines the possibilities for improved land management in Western Australia arising from the development of carbon sinks by considering: (a) the likelihood of a carbon market developing and the likely depth of that market as a result of current national and international policies, (b) the data available to provide estimates on different types of sinks, and (c) the likely benefits of wide-scale sink investment.
It was estimated that the total amount of carbon that could be sequestered by reforesting 16.8 Mha of cleared farmland is 2200 Mt CO2 -e, and between 290 and 1170 Mt CO2 -e by destocking 94.8 Mha of rangelands. There were insufficient data to produce estimates of sequestration following changes in tillage practice in cropping systems or the revegetation of already salinized land. We conclude that carbon sinks are only likely to become profitable as a broad-scale stand-alone enterprise when carbon prices reach AUD$15/t CO2 -e, with this threshold value varying with carbon yield and project costs. Below this price, their value can be significant as an adjunct to reforestation schemes that are aimed at providing other products (wood, pulp, bioenergy) and land and water conservation benefits. Irrespective of this, carbon sinks provide an opportunity to both sequester carbon in a least-cost fashion and improve soil and watershed management.
ABSTRACT: Conservation agriculture (CA), defined as minimal soil disturbance (no-till) and permanent soil cover (mulch) combined with rotations, is a more sustainable cultivation system for the future than those presently practised. The present paper first introduces the reasons for tillage in agriculture and discusses how this age-old agricultural practice is responsible for the degradation of natural resources and soils. The paper goes on to introduce conservation tillage (CT), a minimum tillage and surface mulch practice that was developed in response to the severe wind erosion caused by mouldboard tillage of grasslands and referred to as the American dust bowl of the 1930s. CT is then compared with CA, a suggested improvement on CT, where no-till, mulch, and rotations significantly improve soil properties (physical, biological, and chemical) and other biotic factors, enabling more efficient use of natural resources. CA can improve agriculture through improvement in water infiltration and reducing erosion, improving soil surface aggregates, reducing compaction through promotion of biological tillage, increasing surface soil organic matter and carbon content, moderating soil temperatures, and suppressing weeds. CA also helps reduce costs of production, saves time, increases yield through more timely planting, reduces diseases and pests through stimulation of biological diversity, and reduces greenhouse gas emissions. Availability of suitable equipment is a major constraint to successful CA, but advances in design and manufacture of seed drills by local manufacturers are enabling farmers to experiment and accept this technology in many parts of the world. Estimates of farmer adoption of CA are close to 100 million ha in 2005, indicating that farmers are convinced of the benefits of this technology. The paper concludes that agriculture in the next decade will have to produce more food, sustainably, from less land through more efficient use of natural resources and with minimal impact on the environment in order to meet growing population demands. This will be a significant challenge for agricultural scientists, extension personnel, and farmers. Promoting and adopting CA management systems can help meet this complex goal.
Hutchinson, J.J., Campbell, C.A., Desjardins, R.L. (2007). Some perspectives on carbon sequestration in agriculture: the contribution of agriculture to the state of climate. Agricultural and Forest Meteorology 142 (2-4): 288-302
ABSTRACT: One of the main options for greenhouse gas (GHG) mitigation identified by the IPCC is the sequestration of carbon in soils. Since the breaking of agricultural land in most regions, the carbon stocks have been depleted to such an extent, that they now represent a potential sink for CO2 removal from the atmosphere. Improved management will however, be required to increase the inputs of organic matter in the top soil and/or decrease decomposition rates. In this paper we use data from selected regions to explore the global potential for carbon sequestration in arable soils. While realising that C sequestration is not limited to the selected regions, we have, however, focussed our review on two regions: (i) Canadian Prairies and (ii) The Tropics. In temperate regions, management changes for an increase in C involve increase in cropping frequency (reducing bare fallow), increasing use of forages in crop rotations, reducing tillage intensity and frequency, better crop residue management, and adopting agroforestry. In the tropics, agroforestry remains the primary method by which sequestration rates may be significantly increased. Increases in soil C may be achieved through improved fertility of cropland/pasture; on extensive systems with shifting cultivation cropped fallows and cover crops may be beneficial, and adopting agro forestry or foresting marginal cropland is also an alternative. In addition, in the tropics it is imperative to reduce the clearing of forests for conversion to cropland. Some regional analyses of soil C sequestration and sequestration potential have been performed, mainly for temperate industrialized North America where the majority of research pertaining to C sequestration has been carried out. More research is needed, especially for the Tropics, to more accurately capture the impact of region-specific interactions between climate, soil, and management of resources on C sequestration, which are lost in global level assessments. By itself, C sequestration in agricultural soils can make only modest contributions (3–6% of fossil fuel contributions) to mitigation of overall greenhouse gas emissions. However, effective mitigation policies will not be based on any single ‘magic bullet’ solutions, but rather on many modest reductions which are economically efficient and which confer additional benefits to society. In this context, soil C sequestration is a significant mitigation option.
Jandl, R., Lindner, M., Vesterdal, L., Bauwens, B., Baritz, R., Hagedorn, F., Johnson, D. W., Minkkinen, K., Byrne, K. A. (2007). How strongly can forest management influence soil carbon sequestration?. Geoderma 137 (3-4): 253-268
ABSTRACT: We reviewed the experimental evidence for long-term carbon (C) sequestration in soils as consequence of specific forest management strategies. Utilization of terrestrial C sinks alleviates the burden of countries which are committed to reducing their greenhouse gas emissions. Land-use changes such as those which result from afforestation and management of fast-growing tree species, have an immediate effect on the regional rate of C sequestration by incorporating carbon dioxide (CO2 ) in plant biomass. The potential for such practices is limited in Europe by environmental and political constraints. The management of existing forests can also increase C sequestration, but earlier reviews found conflicting evidence regarding the effects of forest management on soil C pools. We analyzed the effects of harvesting, thinning, fertilization application, drainage, tree species selection, and control of natural disturbances on soil C dynamics. We focused on factors that affect the C input to the soil and the C release via decomposition of soil organic matter (SOM). The differentiation of SOM into labile and stable soil C fractions is important. There is ample evidence about the effects of management on the amount of C in the organic layers of the forest floor, but much less information about measurable effects of management on stable C pools in the mineral soil. The C storage capacity of the stable pool can be enhanced by increasing the productivity of the forest and thereby increasing the C input to the soil. Minimizing the disturbances in the stand structure and soil reduces the risk of unintended C losses. The establishment of mixed species forests increases the stability of the forest and can avoid high rates of SOM decomposition. The rate of C accumulation and its distribution within the soil profile differs between tree species. Differences in the stability of SOM as a direct species effect have not yet been reported.
ABSTRACT: The carbon cycle binds together earth’s ecosystems and their inhabitants. My intent is to review the global carbon cycle, examine how humans have modified it, and contemplate (from a soil science bias) the new questions that await us on a changing earth. These thoughts are proffered, not to propose a way forward, but to invite conversation about opportunities that await us.
Terrestrial ecosystems hold a lot of carbon—about 500 Pg C in plant biomass, and 2000 Pg C in soil organic matter. Oceans contain even more. And the atmosphere, now with about 785 Pg C, connects all of these pools. The flows of carbon between the pools, and their feedbacks, have kept atmospheric CO2 reasonably constant for millennia. But humans have increasingly distorted the balance, by changing land use and by injecting fossil C back into the cycle. Consequently, atmospheric CO2 has increased recently by more than 3 Pg C per year and, by century’s end, its concentration may be twice pre-industrial levels, or more.
The changing carbon cycle poses new questions for scientists. Now we will be asked, not how things are, but how they will be. For example: How will changes in CO2 alter flows of carbon through biological carbon stocks? Can we manage ecosystems to hold more carbon? Are current carbon stores vulnerable should the earth warm, or water cycles shift, or nitrogen flows be altered? What will the C cycle look like a century from now; and will it then still provide all that we expect from it? These and other new questions may elicit from us fresh insights and approaches.We may learn to look more broadly at the C cycle, seeing all the ‘ecosystem services’ (not just C sequestration). We may insist on studies yielding deeper understanding of the C cycle, relevant beyond current issues. We may further emphasize ‘time’ in our studies, looking more at flows and changes than at describing what is—and looking long enough to see even subtle shifts.We may learn to follow C beyond the usual boundaries set by arbitrary disciplines. And we may come to see, more than before, how the carbon cycle weaves through our fields and skies and forests—and find new ways to reveal its grandeur to those who have not yet seen it. And then, it may happen that
our successors, a century from now, will look back, almost in envy, at the urgent, enticing questions we were given to solve.
Johnson, J.M.F., Reicosky, D.C., Allmaras, R.R., Sauer, T.J., Venterea, R.T., Dell, C.J. (2005). Greenhouse gas contributions and mitigation potential of agriculture in the central USA. Soil and Tillage Research 83 (1): 73-94
ABSTRACT: The central USA contains some of the most productive agricultural land of the world. Due to the high proportion of land area committed to crops and pasture in this region, the carbon (C) stored and greenhouse gas (GHG) emission due to agriculture represent a large percentage of the total for the USA. Our objective was to summarize potential soil organic C (SOC) sequestration and GHG emission from this region and identify how tillage and cropping system interact to modify these processes. Conservation tillage (CST), including no-tillage (NT), has become more widespread in the region abating erosion and loss of organic rich topsoil and sequestering SOC. The rate of SOC storage in NT compared to conventional tillage (CT) has been significant, but variable, averaging 0.40 ± 0.61 Mg C ha−1 year−1 (44 treatment pairs). Conversion of previous cropland to grass with the conservation reserve program increased SOC sequestration by 0.56 ± 0.60 Mg C ha−1 year−1 (five treatment pairs). The relatively few data on GHG emission from cropland and managed grazing land in the central USA suggests a need for more research to better understand the interactions of tillage, cropping system and fertilization on SOC sequestration and GHG emission.
ABSTRACT: The estimation of soil carbon content is of pressing concern for soil protection and in mitigation strategies for global warming. This paper describes the methodology developed and the results obtained in a study aimed at estimating organic carbon contents (%) in topsoils across Europe. The information presented in map form provides policy-makers with estimates of current topsoil organic carbon contents for developing strategies for soil protection at regional level. Such baseline data are also of importance in global change modelling and may be used to estimate regional differences in soil organic carbon (SOC) stocks and projected changes therein, as required for example under the Kyoto Protocol to the United Nations Framework Convention on Climate Change, after having taken into account regional differences in bulk density.
The study uses a novel approach combining a rule-based system with detailed thematic spatial data layers to arrive at a much-improved result over either method, using advanced methods for spatial data processing. The rule-based system is provided by the pedo-transfer rules, which were developed for use with the European Soil Database. The strong effects of vegetation and land use on SOC have been taken into account in the calculations, and the influence of temperature on organic carbon contents has been considered in the form of a heuristic function. Processing of all thematic data was performed on harmonized spatial data layers in raster format with a 1 km × 1 km grid spacing. This resolution is regarded as appropriate for planning effective soil protection measures at the European level. The approach is thought to be transferable to other regions of the world that are facing similar questions, provided adequate data are available for these regions. However, there will always be an element of uncertainty in estimating or determining the spatial distribution of organic carbon contents of soils.
ABSTRACT: Soils in equilibrium with a natural forest ecosystem have high carbon (C) density. The ratio of soil:vegetation C density increases with latitude. Land use change, particularly conversion to agricultural ecosystems, depletes the soil C stock. Thus, degraded agricultural soils have lower soil organic carbon (SOC) stock than their potential capacity. Consequently, afforestation of agricultural soils and management of forest plantations can enhance SOC stock through C sequestration. The rate of SOC sequestration, and the magnitude and quality of soil C stock depend on the complex interaction between climate, soils, tree species and management, and chemical composition of the litter as determined by the dominant tree species. Increasing production of forest biomass per se may not necessarily increase the SOC stocks. Fire, natural or managed, is an important perturbation that can affect soil C stock for a long period after the event. The soil C stock can be greatly enhanced by a careful site preparation, adequate soil drainage, growing species with a high NPP, applying N and micronutrients (Fe) as fertilizers or biosolids, and conserving soil and water resources. Climate change may also stimulate forest growth by enhancing availability of mineral N and through the CO2 fertilization effect, which may partly compensate release of soil C in response to warming. There are significant advances in measurement of soil C stock and fluxes, and scaling of C stock from pedon/plot scale to regional and national scales. Soil C sequestration in boreal and temperate forests may be an important strategy to ameliorate changes in atmospheric chemistry.
ABSTRACT: World soils have been a major source of enrichment of atmospheric concentration of CO2 ever since the dawn of settled agriculture, about 10,000 years ago. Historic emission of soil C is estimated at 78 ± 12 Pg out of the total terrestrial emission of 136 ± 55 Pg, and post-industrial fossil fuel emission of 270 ± 30 Pg. Most soils in agricultural ecosystems have lost 50 to 75% of their antecedent soil C pool, with the magnitude of loss ranging from 30 to 60 Mg C/ha. The depletion of soil organic carbon (SOC) pool is exacerbated by soil drainage, plowing, removal of crop residue, biomass burning, subsistence or low-input agriculture, and soil degradation by erosion and other processes. The magnitude of soil C depletion is high in coarse-textured soils (e.g., sandy texture, excessive internal drainage, low activity clays and poor aggregation), prone to soil erosion and other degradative processes. Thus, most agricultural soils contain soil C pool below their ecological potential. Adoption of recommend management practices (e.g., no-till farming with crop residue mulch, incorporation of forages in the rotation cycle, maintaining a positive nutrient balance, use of manure and other biosolids), conversion of agriculturally marginal soils to a perennial land use, and restoration of degraded soils and wetlands can enhance the SOC pool. Cultivation of peatlands and harvesting of peatland moss must be strongly discouraged, and restoration of degraded soils and ecosystems encouraged especially in developing countries. The rate of SOC sequestration is 300 to 500 Kg C/ha/yr under intensive agricultural practices, and 0.8 to 1.0 Mg/ha/yr through restoration of wetlands. In soils with severe depletion of SOC pool, the rate of SOC sequestration with adoption of restorative measures which add a considerable amount of biomass to the soil, and irrigated farming may be 1.0 to 1.5 Mg/ha/yr. Principal mechanisms of soil C sequestration include aggregation, high humification rate of biosolids applied to soil, deep transfer into the sub-soil horizons, formation of secondary carbonates and leaching of bicarbonates into the ground water. The rate of formation of secondary carbonates may be 10 to 15 Kg/ha/yr, and the rate of leaching of bicarbonates with good quality irrigation water may be 0.25 to 1.0 Mg C/ha/yr. The global potential of soil C sequestration is 0.6 to 1.2 Pg C/yr which can off-set about 15% of the fossil fuel emissions.
Lasch, Petra, Badeck, Franz-W., Suckow, Felicitas, Lindner, Marcus, Mohr, Peter (2005). Model-based analysis of management alternatives at stand and regional level in Brandenburg (Germany). Forest Ecology and Management 207 (1-2): 59-74
ABSTRACT: The model-based analysis of the effects of management options at stand and regional levels on forest functions such as carbon storage and groundwater recharge provides a basis for optimisation of forest planning under global change. The physiologically based model 4C (‘FORESEE’—FORESt Ecosystems in a changing Environment) can be used to evaluate a broad variety of silvicultural treatments for mono- and mixed-species forest stands. In this study, we present the testing and evaluation of the 4C management submodel, using data from long-term experimental plots in selected stands in the Federal State of Brandenburg, Germany. Comparison of experimental data with model simulations, by means of diameter distributions, demonstrated that the applied thinning operations preserved the diameter distribution of the stands. 4C realistically described the effects of management options on stand dynamics as proved by long-term simulations. Furthermore, the investigation of the effects of management options, thinning intensity, and rotation length on carbon storage in biomass and soil, yield, and groundwater recharge showed the applicability of the model 4C for the evaluation of forest functions in managed forests.
We present the analysis of management effects on forest functions at a regional scale, based on a grid of forest monitoring sites (“Ökologische Waldzustandskontrolle”—ÖWK) in Brandenburg, which is mainly dominated by Scots pine (Pinus sylvestris L.). The model was applied at the sites with three management options under current climate and a climate change scenario (i.e., temperature increase of 1.4 °K by 2055). The results of 50-year simulation runs were analysed for forest growth units with respect to total carbon storage (Csum ) and groundwater recharge. More intensive management decreased the Csum after 50 years and slightly increased groundwater recharge. Climate change led to a reduction of groundwater recharge by about 40%, averaged over all sites. Csum was increased at some sites because of the extension of the growing season in spite of slight decreases in precipitation, but at several other sites, Csum decreased due to increased dryness. The question arises whether these negative effects of climate change can be minimised by adaptive management operations. In this study, we concluded that the potentials of adaptive management based on changes in rotation length and thinning is very limited in this region, which is characterised by poor sites and dry climatic conditions. We concluded that it is necessary to include forest transformation strategies in management impact analyses for forest planning under global change.
R. D. Lasco, M. M. Cardinoza (2007). Baseline carbon stocks assessment and projection of future carbon benefits of a carbon sequestration project in East Timor. Mitigation and Adaptation Strategies for Global Change 12 (2): 243-257
ABSTRACT: Climate change is one of the most pressing environmental problems humanity is facing today. Forest ecosystems serve as a source or sink of greenhouse gases, primarily CO2 . With support from the Canadian Climate Change Fund, the Community-based Natural Resource Management for Carbon Sequestration project in East Timor (CBNRM-ET) was implemented to “maintain carbon (C) stocks and increase C sequestration through the development of community-based resource management systems that will simultaneously improve livelihood security”. Project sites were in the Laclubar and Remexio Sub-districts of the Laclo watershed. The objective of this study was to quantify baseline C stocks and sequestration benefits of project components (reforestation with fast-growing species, primarilyCasuarina equisetifolia , and agroforestry involving integration ofParaserianthes falcataria ). Field measurements show that mature stands (=30 years) ofP. falcataria andC. equisetifolia contain up to 200 Mg C ha-1 in above ground biomass, indicating the vast potential of project sites to sequester carbon. Baseline C stocks in above ground biomass were very low in both Laclubar (6.2 Mg C ha-1 for reforestation sites and 5.2 Mg C ha-1 for agroforestry sites and Remexio (3.0 Mg C ha-1 for reforestation and 2.5 Mg C ha-1 for agroforestry). Baseline soil organic C levels were much higher reaching up to 160 Mg C ha-1 in Laclubar and 70 Mg C ha-1 in Remexio. For the next 25 years, it is projected that 137 671 Mg C and 84 621 Mg C will be sequestered under high- and low C stock scenarios, respectively.
ABSTRACT: Society is increasingly turning attention toward greenhouse gas emission control with for example the Kyoto Protocol has entered into force. Since many of the emissions come from energy use, high cost strategies might be required until new technological developments reduce fossil fuel dependency or increase energy utilization efficiency. On the other hand biologically based strategies may be used to offset energy related emissions. Agricultural soil and forestry are among the largest carbon reservoirs on the planet; therefore, agricultural and forest activities may help to reduce the costs of greenhouse gas emission mitigation. However, sequestration exhibits permanence related characteristics that may influence this role. We examine the dynamic role of carbon sequestration in the agricultural and forest sectors can play in mitigation. A 100-year mathematical programming model, depicting U.S. agricultural and forest sectoral activities including land transfers and greenhouse gas consequences is applied to simulate potential mitigation response. The results show that at low cost and in the near term agricultural soil and forest management are dominant sectoral responses. At higher prices and in the longer term biofuels and afforestation take over. Our results reveal that the agricultural and forest sector carbon sequestration may serve as an important bridge to the future helping to hold costs down until energy emissions related technology develops.
Liebig, M.A., Morgan, J.A., Reeder, J.D., Ellert, B.H., Gollany, H.T., Schuman, G.E. (2005). Greenhouse gas contributions and mitigation potential of agricultural practices in northwestern USA and western Canada. Soil and Tillage Research 83 (1): 25-52
ABSTRACT: Concern over human impact on the global environment has generated increased interest in quantifying agricultural contributions to greenhouse gas fluxes. As part of a research effort called GRACEnet (Greenhouse Gas Reduction through Agricultural Carbon Enhancement Network), this paper summarizes available information concerning management effects on soil organic carbon (SOC) and carbon dioxide (CO2 ), nitrous oxide (N2 O), and methane (CH4 ) fluxes in cropland and rangeland in northwestern USA and western Canada, a region characterized by its inherently productive soils and highly variable climate. Continuous cropping under no-tillage in the region increased SOC by 0.27 ± 0.19 Mg C ha-1 yr-1 , which is similar to the Intergovernmental Panel on Climate Change (IPCC) estimate for net annual change in C stocks from improved cropland management. Soil organic C sequestration potential for rangelands was highly variable due to the diversity of plant communities, soils, and landscapes, underscoring the need for additional long-term C cycling research on rangeland. Despite high variability, grazing increased SOC by 0.16 ± 0.12 Mg C ha-1 yr-1 and converting cropland or reclaimed mineland to grass increased SOC by 0.94 ± 0.86 Mg C ha-1 yr-1 . Although there was generally poor geographical coverage throughout the region with respect to estimates of N2 O and CH4 flux, emission of N2 O was greatest in irrigated cropland, followed by non-irrigated cropland, and rangeland. Rangeland and non-irrigated cropland appeared to be a sink for atmospheric CH4 , but the size of this sink was difficult to determine given the few studies conducted. Researchers in the region are challenged to fill the large voids of knowledge regarding CO2 , N2 O, and CH4 flux from cropland and rangeland in the northwestern USA and western Canada, as well as integrate such data to determine the net effect of agricultural management on radiative forcing of the atmosphere.
Martens, D. A., Emmerich, W., McLain, J. E.T., Johnsen, T. N. (2005). Atmospheric carbon mitigation potential of agricultural management in the southwestern USA. Soil and Tillage Research 83 (1): 95-119
ABSTRACT: Agriculture in the southwestern USA is limited by water supply due to high evaporation and limited seasonal precipitation. Where water is available, irrigation allows for production of a variety of agricultural and horticultural crops. This review assesses the impacts of agriculture on greenhouse gas emission and sequestration of atmospheric C in soils of the hot, dry region of the southwestern USA. In Texas, conservation tillage increased soil organic C by 0.28 Mg C ha-1 year-1 compared with more intensive tillage. Conversion of tilled row crops to the conservation reserve program or permanent pastures increased soil organic C by 0.32 ± 0.50 Mg C ha-1 year-1 . Soil organic C sequestration was dependent on rotation, previous cropping, and type of conservation tillage employed. Relatively few studies have interfaced management and C cycling to investigate the impacts of grazing management on soil organic C, and therefore, no estimate of C balance was available. Irrigated crop and pasture land in Idaho had soil organic C content 10-40 Mg C ha-1 greater than in dryland, native grassland. Soil salinity must be controlled in cropland as soil organic C content was lower with increasing salinity. Despite 75% of the region's soils being classified as calcic, the potential for sequestration of C as soil carbonate has been only scantly investigated. The region may be a significant sink for atmospheric methane, although in general, trace gas flux from semiarid soils lacks adequate characterization. Agricultural impacts on C cycling will have to be better understood in order for effective C sequestration strategies to emerge.
ABSTRACT: Wetlands are among the most important natural resources on earth. They are the sources of cultural, economic and biological diversity. With their wealth of stored carbon, wetlands provide a potential sink for atmospheric carbon, but if not managed properly could become sources of greenhouse gases (GHGs) such as carbon dioxide and methane. Two important long-term uncertainties have initiated much debate in the scientific community. These are global wetland area and the amount of carbon stored in it. Compilation of relevant databases could be useful in setting up a long-term strategy for wetland conservation. It has been difficult to estimate the net carbon sequestration potential of a wetland, because the rate of decomposition of organic matter and the abundance of methanogenic micro-organisms and fluxes from the sediment are extremely complex, and there are often gaps in relevant scientific knowledge. The present discussion on density distribution of soil organic C in global wetlands could well be instrumental in formulating efficient strategies related to carbon sequestration and reduction of GHG emissions in wetland ecosystems. Effective assessment of wetlands will only take place when the available information becomes accessible and usable for all stakeholders.
Neilson, E.T., MacLean, D.A., Meng, F.-R., Arp, P.A. (2007). Spatial distribution of carbon in natural and managed stands in an industrial forest in New Brunswick, Canada. Forest Ecology and Management 253 (1-3): 148-160
ABSTRACT: Industrial forest could be managed to enhance carbon (C) sequestration together with other ecological and socio-economic objectives. However, this requires quantifying C dynamics of all major forest types within the management area, over the whole forest rotation. We used data from permanent sample plots and temporary forest development survey plots to generate volume yield curves and used the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) to estimate C yield and dynamics over a rotation for major forest types in northern New Brunswick, Canada. We compared C yields of natural versus managed and hardwood versus softwood forest under different silviculture treatments over the entire rotation. Carbon in 40–80-year-old and > 80-year-old tolerant hardwood stands averaged about 115 and 130–142 t ha−1, respectively, while softwood spruce (Picea sp.)–balsam fir (Abies balsamea (L.) Mill.) 40–80 and > 80 years old averaged 90 and 88–94 t C ha−1 . Among 10 stand types, total C ranged from 50 to 109 t ha−1 at age 50 years, 92–138 t ha−1 at age 100, and 79–145 t ha−1 at age 150 years. C in most stand types declined from age 100 to 150 years, except for eastern white cedar (Thuja occidentalis L.), sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britton). At age 100 years, planted softwood stands had 94–135 t ha−1 , versus 92–117 t ha−1 for natural softwoods and 127–138 t ha−1 for natural hardwoods. Planted white spruce (Picea glauca (Moench) Voss) and natural sugar maple and yellow birch sequestered the most C. The total C (above and belowground biomass and deadwood, excluding soil carbon) on the 428,000 ha test landbase was 35 million tonnes, or an average of 82 t ha−1 .
ABSTRACT: Carbon sequestration has been well recognized as a viable option to slow the rise in atmospheric greenhouse gas concentration. The main goals of this study were to assess the carbon sequestration potential (CSP) by afforestation of marginal agricultural land (MagLand) and to identify hotspots for potential afforestation activities in the U.S. Midwest region (Michigan (MI), Indiana (IN), Ohio, Kentucky (KY), West Virginia, Pennsylvania (PA) and Maryland (MD)). The 1992 USGS National Land Cover Dataset and the State Soil Geographic (STATSGO) database were used to determine MagLand. Two forest types (coniferous and deciduous) and two management practices (short-rotation versus permanent forest) were combined to form four afforestation scenarios. Simulation models were employed to predict changes in four carbon pools: aboveground biomass, roots, forest floor, and soil organic carbon (SOC). A scenario-generating tool was developed to detect the hotspots. We estimated that there was a total of 6.5 million hectares (Mha) MagLand available in the U.S. Midwest region, which accounts for approximately 24% of the regional total agricultural land. The CSP capacity was predicted to be 508–540 Tg C (1 Tg = 1012 g) over 20 years and 1018–1080 Tg C over 50 years. The results indicate that afforestation of MagLand could offset 6–8% of current CO2 emissions by combustion of fossil fuel in the region. This analysis showed only slight differences in carbon sequestration between forest types or between short-rotation and permanent forest scenarios. Note that this calculation assumed that all suitable MagLand in the U.S. Midwest region was converted to forest and that “best carbon management” was adopted. The actual CSP could be less if the economical and social factors are taken into account. The most preferred locations for implementing the afforestation strategy were found to be concentrated along a west-east axis across the southern parts of Indiana, Ohio, and Pennsylvania, as well as in an area covering southern Michigan and northern parts of Indiana and Ohio. Overall, we conclude that afforestation of MagLand in the Midwest U.S. region offers great potential for carbon sequestration. Future studies are needed to evaluate its economic feasibility, social acceptability, and operation capability.
ABSTRACT: Agriculture currently contributes significantly to the increase of CO2 in the atmosphere, primarily through the conversion of native ecosystems to agricultural uses in the tropics. Yet there are major opportunities for mitigation of CO2 and other greenhouse gas emissions through changes in the use and management of agricultural lands. Agricultural mitigation options can be broadly divided into two categories: (I) strategies to maintain and increase stocks of organic C in soils (and biomass), and (ii) reductions in fossil C consumption, including reduced emissions by the agricultural sector itself and through agricultural production of biofuels to substitute for fossil fuels. Reducing the conversion of new land to agriculture in the tropics could substantially reduce CO2 emissions, but this option faces several difficult issues including population increase, land tenure and other socio-political factors in developing countries. The most significant opportunities for reducing tropical land conversions are in the humid tropics and in tropical wetlands. An important linkage is to improve the productivity and sustainability of existing agricultural lands in these regions. Globally, we estimate potential agricultural CO2 mitigation through soil C sequestration to be 0.4-0.9 Pg C y-1 , through better management of existing agricultural soils, restoration of degraded lands, permanent "set-asides" of surplus agricultural lands in temperate developed countries and restoration of 10-20% of former wetlands now being used for agriculture. However, soils have a finite capacity to store additional C and therefore any increases in C stocks following changes in management would be largely realized within 50-100 years. Mitigation potential through reducing direct agricultural emissions is modest, 0.01-0.05 Pg C y-1 . However, the potential to offset fossil C consumption through the use of biofuels produced by agriculture is substantial, 0.5-1.6 Pg C y-1 , mainly through the production of dedicated biofuel crops with a smaller contribution (0.2-0.3 Pg C y-1 ) from crop residues. Many agricultural mitigation options represent "win-win" situations, in that there are important side benefits, in addition to CO2 mitigation, that could be achieved, e.g. improved soil fertility with higher soil organic matter, protection of lands poorly suited for permanent agriculture, cost saving for fossil fuel inputs and diversification of agricultural production (e.g. biofuels). However, the needs for global food production and farmer/societal acceptability suggest that mitigation technologies should conform to: (I) the enhancement of agricultural production levels in parts of the world where food production and population demand are in delicate balance and (ii) the accrual of additional benefits to the farmer (e.g., reduced labor, reduced or more efficient use of inputs) and society at large.
ABSTRACT: Agriculture is targeted to make a substantial contribution to Canada's greenhouse gas reduction targets under the Kyoto Protocol. To achieve a net reduction in emissions any gains in soil organic carbon storage cannot come at the expense of enhanced nitrous oxide emissions from the soil. In nonlevel agricultural landscapes of the Canadian Prairies the potential for significant soil organic carbon gain due to adoption of soil conserving practices is greatest on convex upper slope positions, which have experienced major losses of soil organic carbon due to cultivation. The potential for soil organic carbon gain in lower slope positions is limited due to their high soil organic carbon contents, but targeted wetland and riparian vegetation restoration programs could lead to significant above ground carbon gains. Several studies have shown that emissions of nitrous oxide from lower slope positions are significantly higher than the convex slope positions, and that improvements in nitrogen fertilizer use efficiency through site-specific management has the potential to significantly reduce nitrous oxide (N2 O) emissions from these positions. Because of the close relationship between landform position and the key carbon and nitrogen processes, quantitative landform segmentation procedures can be used to delineate precision conservation management zones in these landscapes. Site-specific management practices such as reduced or no-till, seeding to grass, wetland restoration, and site-specific nitrogen (N) management can then be implemented to simultaneously increase soil organic carbon stores on eroded upper slope segments while preserving existing stores of soil organic carbon and reducing N2 O emissions from lower slope segments. Close cooperation between precision conservation professionals and agronomists is required to ensure that information required by producers is available to guide them in their decision making and implementation of precision conservation for co-management of carbon and nitrogen.
Schmid, S., Thurig, E., Kaufmann, E., Lischke, H., Bugmann, H. (2006). Effect of forest management on future carbon pools and fluxes: A model comparison. Forest Ecology and Management 237 (1-3): 65-82
ABSTRACT: Currently, there is a strong demand for estimates of the current and potential future carbon sequestration in forests, the role of management practices, and the temporal duration of biotic carbon sinks. Different models, however, lead to different projections. Model comparisons allow us to assess the range of potential ecosystem responses, and they facilitate the detection of the strengths and weaknesses of particular models. In this study, the empirical, individual-based forest models MASSIMO, the semi-empirical individual-based forest models SILVA – both combined with the soil model YASSO – and the process-based, biogeochemical model Biome-BGC were used to assess the above- and belowground carbon pools and net fluxes of several forested regions in Switzerland for the next 100 years under four different management scenarios: (1) the current harvest amounts were used, (2) harvest was intensified by reducing the amount of large tree dimensions, (3) harvest was reduced to a minimum by only maintaining the protection function in mountain forests and avoiding pests and diseases, and (4) harvest was adjusted to achieve maximum sustainable growth. The results show that the three models projected similar patterns of net carbon fluxes. The models estimated that in the absence of large-scale disturbances the forest biomass and soil carbon can be increased, particularly under scenario 2, and therefore, forests can be used as carbon sinks. These sinks were estimated to last for a maximum of 100 years. Differences between the management scenarios depend on the time period considered: either net carbon fluxes are maximized at a short term (30–40 years) or at a longer term (100 years or more). In contrast to the similar carbon fluxes, some carbon pools projected by the models differed strongly. These differences in model behaviour can be attributed to model-specific responses to the strongly heterogeneous Swiss climate conditions and to different model assumptions. To find the optimum strategy in terms of not only maximizing carbon sequestration but climate protection, it is essential to account for wood-products and particularly substitution of fossil fuel in the model simulations.
ABSTRACT: There is interest in society in general and in the agricultural and forestry sectors concerning a land-based role in greenhouse gas mitigation reduction. Numerous studies have estimated the potential supply schedules at which agriculture and forestry could produce greenhouse gas offsets. However, such studies vary widely in critical assumptions regarding economic market adjustments, allowed scope of mitigation alternatives, and region of focus. Here, we examine the effects of using different assumptions on the total emission mitigation supply curve from agriculture and forestry in the United States. To do this we employ the U.S.-based Agricultural Sector and Mitigation of Greenhouse Gas Model and find that variations in such factors can have profound effects on the results. Differences between commonly employed methods shift economic mitigation potentials from -55 to + 85%. The bias is stronger at higher carbon prices due to afforestation and energy crop plantations that reduce supply of traditional commodities. Lower carbon prices promote management changes with smaller impacts on commodity supply.
ABSTRACT: This paper provides a method for estimating the marginal cost of soil carbon (C) derived from setting aside highly erodible cropland in the United States. Increases in soil carbon are estimated using a modified Intergovernmental Panel on Climate Change soil organic carbon inventory method and National Resources Inventory data. Marginal costs of soil carbon sequestration activities are based on the opportunity cost of removing highly erodible land from crop production using land rental rates adjusted to account for the productivity of cropland and Conservation Reserve Program rental rates. Total soil carbon sequestration from setting aside highly erodible land is over 10 Tg C yr−1 (11.0 Mtn C yr−1 ) on the 21.9 Mha (54.1 Mac) where corn, cotton, sorghum, soybean, wheat, or fallow were grown in 1997. The marginal cost of stored carbon based on these estimates range from $11 to $4,492 Mg−1 C ($10 to $4,075 tn−1 C) with a US weighted average of $288 Mg−1 C ($261tn−1 C). Changes in US crop production levels from removing land from crop production are also estimated.
Terra, J. A., Reeves, D. W., Shaw, J. N., Raper, R. L. (2005). Impacts of landscape attributes on carbon sequestration during the transition from conventional to conservation management practices on a Coastal Plain field. Journal of Soil and Water Conservation 60 (6): 438-446
ABSTRACT: Field-scale experiments on degraded soils comparing management systems would facilitate a better understanding of the soil organic carbon (C) landscape dynamics associated with transition to conservation systems. We assessed the effects of soil management practices and terrain attributes on soil organic C in a 9 ha (22.2 ac) Alabama field (Typic and Aquic Paleudults). Treatments were established in strips across the landscape in a corn (Zea mays L.)-cotton (Gossypium hirsutum L.) rotation. Treatments included a conventional system (chisel plowing/disking without cover crops) with or without dairy manure, and a conservation system (no-till and cover crops) with and without manure. A soil survey, topography, soil electrical conductivity, initial soil organic C and soil texture were used to delineate management zones or clusters. After one rotation cycle (30 months), averaged across 240 positions distributed over the entire field, no-till or conventional tillage + manure increased soil organic C (0 to 5 cm; 0 to 2 in depth) by -50 percent compared to conventional tillage (7.34 and 7.62 vs. 5.02 Mg ha−1 ; 3.28 and 3.40 vs. 2.24 t ac−1 , respectively); but no-till+manure increased soil organic C by 157 percent. Initial soil organic C content was the most common correlated variable with soil organic C changes (SOC) across the landscape for all treatments and conservation systems had greater soil organic C increases relative to conventional systems at low soil quality landscape positions. Our results show the potential to sequester C using high-residue producing conservation systems and manure is scale dependent, and may be higher than previously expected for degraded soils in the southeastern United States.
ABSTRACT: Carbon sequestered in biomass is not necessarily stored infinitely, but is exposed to human or natural disturbances. Storm is the most important natural disturbance agent in Swiss forests. Therefore, if forests are taken into account in the national carbon budget, the impact of windthrow on carbon pools and fluxes should be included. In this article the forest scenario model MASSIMO and the soil carbon model YASSO were applied to assess the effect of forest management and an increased storm activity on the carbon sequestration in Swiss forests. First, the soil model was adapted to Swiss conditions and validated. Second, carbon fluxes were assessed applying the two models under various forest management scenarios and storm frequencies. In particular, the influence of clearing after a storm event on the carbon budget was analyzed. The evaluation of the model results showed that the soil model reliably reproduces the amount of soil carbon at the test sites. The simulation results indicated that, within the simulated time period of 40 years, forest management has a strong influence on the carbon budget. However, forest soils only react slightly to changes in the above-ground biomass. The results also showed that a storm frequency increase of 30% has a small impact on the national carbon budget of forests. To develop effective mitigation strategies for forest management, however, longer time periods must be regarded.
ABSTRACT: Studies of carbon and nitrogen dynamics in ecosystems are leading to an understanding of the factors and mechanisms that affect the inputs to and outputs from soils and how these might be manipulated to enhance C sequestration. Both the quantity and the quality of soil C inputs influence C storage and the potential for C sequestration. Changes in tillage intensity and crop rotations can also affect C sequestration by changing the soil physical and biological conditions and by changing the amounts and types of organic inputs to the soil. Analyses of changes in soil C and N balances are being supplemented with studies of the management practices needed to manage soil carbon and the implications for fossil-fuel use, emission of other greenhouse gases (such as N2 O and CH4 ), and impacts on agricultural productivity. The Consortium for Research on Enhancing Carbon Sequestration in Terrestrial Ecosystems (CSiTE) was created in 1999 to perform fundamental research that will lead to methods to enhance C sequestration as one component of a C management strategy. Research to date at one member of this consortium, Oak Ridge National Laboratory, has focused on C sequestration in soils and we begin here to draw together some of the results.
ABSTRACT: The STANDCARB 2.0 model was used to examine the effects of partial harvest of trees within stands on forest-related carbon (C) stores in a typical Pacific NorthwestPseudotsuga /Tsuga forest. For harvest rotation intervals of 20 to 250 years the effect of completely dispersed (that is, a checkerboard) versus completely aggregated cutting patterns (that is, single blocks) was compared. The simulations indicated that forests with frequent, but partial removal of live trees can store as much C as those with complete tree harvest on less frequent intervals. Stores in forest products generally declined as the fraction of live trees harvested declined and as the interval between harvests increased. Although the proportion of total system stores in forest products increased as the frequency of harvests and proportion of trees removed increased, this did not offset the reduction in forest C stores these treatments caused. Spatial arrangement of harvest influenced tree species composition profoundly; however, the effects of aggregated versus dispersed cutting patterns on C stores were relatively small compared to the other treatments. This study indicates that there are multiple methods to increase C stores in the forest sector including either increasing the time between harvests or reducing the fraction of trees harvested during each harvest.
K. van Groenigen, J. Six, B. A. Hungate, M. de Graaff, N. van Breemen, C. van Kessel (2006). Element interactions limit soil carbon storage. Proceedings Of The National Academy Of Sciences Of The United States Of America 103 (17): 6571-6574
ABSTRACT: Rising levels of atmospheric CO2 are thought to increase C sinks in terrestrial ecosystems. The potential of these sinks to mitigate CO2 emissions, however, may be constrained by nutrients. By using metaanalysis, we found that elevated CO2 only causes accumulation of soil C when N is added at rates well above typical atmospheric N inputs. Similarly, elevated CO2 only enhances N2 fixation, the major natural process providing soil N input, when other nutrients (e.g., phosphorus, molybdenum, and potassium) are added. Hence, soil C sequestration under elevated CO2 is constrained both directly by N availability and indirectly by nutrients needed to support N2 fixation.
ABSTRACT: This paper reviews the effects of past forest management on carbon stocks in the United States, and the challenges for managing forest carbon resources in the 21st century. Forests in the United States were in approximate carbon balance with the atmosphere from 1600–1800. Utilization and land clearing caused a large pulse of forest carbon emissions during the 19th century, followed by regrowth and net forest carbon sequestration in the 20th century. Recent data and knowledge of the general behavior of forests after disturbance suggest that the rate of forest carbon sequestration is declining. A goal of an additional 100 to 200 Tg C/yr of forest carbon sequestration is achievable, but would require investment in inventory and monitoring, development of technology and practices, and assistance for land managers.
ABSTRACT: Three scenarios of the Conservation Reserve Program (CRP) were simulated to project carbon (C) pools and fluxes of associated grassland and forestland for the years 1986-2035; and to evaluate the potential to offset greenhouse gas emissions through C sequestration. The approach was to link land-area enrolments with grassland and forestland C densities to simulate C pools and fluxes over 50 years. The CRP began in 1986 and by 1996 consisted of 16.2× 106 ha cropland converted to 14.7× 106 ha grassland and of 1.5× 106 ha forestland. The CRP1 simulated the likely outcome of the CRP as contracts expire in 1996 with the anticipated return of 8.7× 106 ha grassland and of 0.4× 106 ha forestland to crop production. The CRP2 assumed that the CRP continues with no land returning to crop production. The CRP3 was an expansion of the CRP2 to include afforestation of 4×106 ha new land. Average net annual C gains for the years 1996-2005 were <1, 12, and 16 TgC yr-1 for CRP1, CRP2, and CRP3, respectively. Afforestation of marginal cropland as simulated under CRP3 could provide approximately 15% of the C offset needed to attain the Climate Change Action Plan of reducing greenhouse gas emmissions to their 1990 level by the year 2000 within the United States.
ABSTRACT: Rising CO2 concentrations in the atmosphere could alter Earth's climate system, but it is thought that higher concentrations may improve plant growth through a process known as the “fertilization effect”. Forests are an important part of the planet's carbon cycle, and sequester a substantial amount of the CO2 released into the atmosphere by human activities. Many people believe that the amount of carbon sequestered by forests will increase as CO2 concentrations rise. However, an increasing body of research suggests that the fertilization effect is limited by nutrients and air pollution, in addition to the well documented limitations posed by temperature and precipitation. This review suggests that existing forests are not likely to increase sequestration as atmospheric CO2 increases. It is imperative, therefore, that we manage forests to maximize carbon retention in above- and belowground biomass and conserve soil carbon.
G.M. Blate, L.A. Joyce, J. S. Littell, S.G. McNulty, C. I. Millar, S.C. Moser, R.P. Neilson, K. O’Halloran, D.L. Peterson (2009). Adapting to climate change in United States national forests. Unasylva 60 (231-232): 57-62
FIRST PARAGRAPH: Climate change is already affecting forests and other ecosystems, and additional, potentially more severe impacts are expected (IPCC, 2007; CCSP, 2008a, 2008b). As a result, forest managers are seeking practical guidance on how to adapt their current practices and, if necessary, their goals. Adaptations of forest ecosystems, which in this context refer to adjustments in management (as opposed to “natural” adaptation), ideally would reduce the negative impacts of climate change and help managers take advantage of any positive impacts.
This article summarizes key points from a review of climate change adaptation options for United States national forests (Joyce et al., 2008) produced under the auspices of the United States Climate Change Science Program (CCSP) (see Box). The study sought to provide practical information on potential adaptation options for resource managers by asking:
• How will climate change affect the ability of resource managers to achieve their management goals?
• What might a resource manager do to prepare the management system for climate change impacts while maintaining current goals (and constantly evaluating if these goals need to be modified or re-prioritized)?
ABSTRACT: While there is no question that successful mitigation strategies remain critical in the quest to avoid worst-case climate change scenarios, we’ve passed the point where mitigation efforts alone can deal with the problems that climate change is creating. Because of “committed” warming – climate change that will occur regardless of mitigation measures, a result of the already-accumulated greenhouse gases in the atmosphere – what happens to social-ecological systems over the next decades, and most likely over the next few centuries, will largely be beyond human control. The time to start preparing for these changes is now, by making adaptation part of a national climate change policy.
Nevertheless, American law and policy are not keeping up with the need for adaptation, even though adapting law to a world of continuing climate change impacts will be a far more complicated task than addressing mitigation. Environmental and natural resources law, for example, are currently based on assumptions of ecological stationarity and pursue goals of preservation and restoration. Neither those assumptions nor those goals fit a world of continual, unpredictable, and nonlinear transformations of complex ecosystems – but that is the world that climate change impacts are creating.
This Article argues for a principled flexibility model of climate change adaptation law to pursue goals of increasing the resilience and adaptive capacity of social-ecological systems. In so doing, it lays out five principles and several sub-principles for the law of environmental regulation and natural resources management. Structurally, this Article also strongly suggests that climate change adaptation law must be bimodal: it must promote informed and principled flexibility when dealing with climate change impacts, especially impacts that affect baseline ecological conditions such as temperature and hydrology, while simultaneously embracing an unyielding commitment to precautionary regulation when dealing with everything else.
ABSTRACT: When included as part of a larger greenhouse gas (GHG) emissions reduction program, forest offsets may provide low-cost opportunities for GHG mitigation. One barrier to including forest offsets in climate policy is the risk of reversal, the intentional or unintentional release of carbon back to the atmosphere due to storms, fire, pests, land use decisions, and many other factors. To address this shortcoming, a variety of different strategies have emerged to minimize either the risk or the financial and environmental implications of reversal. These strategies range from management decisions made at the individual stand level to buffers and set-asides that function across entire trading programs. For such strategies to work, the actual risk and magnitude of potential reversals need to be clearly understood. In this paper we examine three factors that are likely to influence reversal risk: natural disturbances (such as storms, fire, and insect outbreaks), climate change, and landowner behavior. Although increases in atmospheric CO2 and to a lesser extent warming will likely bring benefits to some forest ecosystems, temperature stress may result in others. Furthermore, optimism based on experimental results of physiology and growth must be tempered with knowledge that future large-scale disturbances and extreme weather events are also likely to increase. At the individual project level, management strategies such as manipulation of forest structure, age, and composition can be used to influence carbon sequestration and reversal risk. Because some management strategies have the potential to maximize risk or carbon objectives at the expense of the other, policymakers should ensure that forest offset policies and programs do not provide the singular incentive to maximize carbon storage. Given the scale and magnitude of potential disturbance events in the future, however, management decisions at the individual project level may be insufficient to adequately address reversal risk; other, non-silvicultural strategies and policy mechanisms may be necessary. We conclude with a brief review of policy mechanisms that have been developed or proposed to help manage or mitigate reversal risk at both individual project and policy-wide scales.
ABSTRACT: Management of forests for carbon uptake is an important tool in the effort to slow the increase in atmospheric CO2 and global warming. However, some current policies governing forest carbon credits actually promote avoidable CO2 release and punish actions that would increase long-term carbon storage. In fire-prone forests, management that reduces the risk of catastrophic carbon release resulting from stand-replacing wild-fire is considered to be a CO2 source, according to current accounting practices, even though such management may actually increase long-term carbon storage. Examining four of the largest wildfires in the US in 2002, we found that, for forest land that experienced catastrophic stand-replacing fire, prior thinning would have reduced CO2 release from live tree biomass by as much as 98%. Altering carbon accounting practices for forests that have historically experienced frequent, low-severity fire could provide an incentive for forest managers to reduce the risk of catastrophic fire and associated large carbon release events.
Joyce, L.A., G.M. Blate, J. S. Littell, S.G. McNulty, C.I. Millar, S.C. Moser, R.P. Neilson, K. A. O’Halloran, D.L. Peterson, Julius, S.H., J.M. West (2008). National Forests. U.S. Environmental Protection Agency: 3-1 to 3-127
SUMMARY: The National Forest System (NFS) is composed of 155 national forests (NFs) and 20 national grasslands (NGs), which encompass a wide range of ecosystems, harbor much of the nation’s biodiversity, and provide myriad goods and services. The mission of the U.S. Forest Service (USFS), which manages the NFS, has broadened from water and timber to sustaining ecosystem health, diversity, and productivity to meet the needs of present and future generations. The evolution of this mission reflects changing societal values (e.g., increasing emphasis on recreation, aesthetics, and biodiversity conservation), a century of new laws, increasing involvement of the public and other agencies in NF management, and improved ecological understanding. Climate change will amplify the already difficult task of managing the NFS for multiple goals. This chapter offers potential adaptation approaches and management options that the USFS might adopt to help achieve its NF goals and objectives in the face of climate change.
EXECUTIVE SUMMARY: Observations show that warming of the climate is unequivocal. The global warming observed over the past 50 years is due primarily to human-induced emissions of heat-trapping gases. These emissions come mainly from the burning of fossil fuels (coal, oil, and gas), with important contributions from the clearing of forests, agricultural practices, and other activities.
Warming over this century is projected to be considerably greater than over the last century. The global average temperature since 1900 has risen by about 1.5ºF. By 2100, it is projected to rise another 2 to 11.5ºF. The U.S. average temperature has risen by a comparable amount and is very likely to rise more than the global average over this century, with some variation from place to place. Several factors will determine future temperature increases. Increases at the lower end of this range are more likely if global heat-trapping gas emissions are cut substantially. If emissions continue to rise at or near current rates, temperature increases are more likely to be near the upper end of the range. Volcanic eruptions or other natural variations could temporarily counteract some of the human-induced warming, slowing the rise in global temperature, but these effects would only last a few years.
Reducing emissions of carbon dioxide would lessen warming over this century and beyond. Sizable early cuts in emissions would significantly reduce the pace and the overall amount of climate change. Earlier cuts in emissions would have a greater effect in reducing climate change than comparable reductions made later. In addition, reducing emissions of some shorter-lived heat-trapping gases, such as methane, and some types of particles, such as soot, would begin to reduce warming within weeks to decades.
Climate-related changes have already been observed globally and in the United States. These include increases in air and water temperatures, reduced frost days, increased frequency and intensity of heavy downpours, a rise in sea level, and reduced snow cover, glaciers, permafrost, and sea ice. A longer ice-free period on lakes and rivers, lengthening of the growing season, and increased water vapor in the atmosphere have also been observed. Over the past 30 years, temperatures have risen faster in winter than in any other season, with average winter temperatures in the Midwest and northern Great Plains increasing more than 7ºF. Some of the changes have been faster than previous assessments had suggested.
These climate-related changes are expected to continue while new ones develop. Likely future changes for the United States and surrounding coastal waters include more intense hurricanes with related increases in wind, rain, and storm surges (but not necessarily an increase in the number of these storms that make landfall), as well as drier conditions in the Southwest and Caribbean. These changes will affect human health, water supply, agriculture, coastal areas, and many other aspects of society and the natural environment.
This report synthesizes information from a wide variety of scientific assessments (see page 7) and recently published research to summarize what is known about the observed and projected consequences of climate change on the United States. It combines analysis of impacts on various sectors such as energy, water, and transportation at the
national level with an assessment of key impacts on specific regions of the United States. For example, sea-level rise will increase risks of erosion, storm surge damage, and flooding for coastal communities, especially in the Southeast and parts of Alaska. Reduced snowpack and earlier snow melt will alter the timing and amount of water supplies, posing
significant challenges for water resource management in the West. (Continued)
ABSTRACT: The increase in atmospheric concentration of CO2 by 31% since 1750 from fossil fuel combustion and land use change necessitates identification of strategies for mitigating the threat of the attendant global warming. Since the industrial revolution, global emissions of carbon (C) are estimated at 270±30 Pg (Pg=petagram=1015 G=1 billion ton) due to fossil fuel combustion and 136±55 Pg due to land use change and soil cultivation. Emissions due to land use change include those by deforestation, biomass burning, conversion of natural to agricultural ecosystems, drainage of wetlands and soil cultivation. Depletion of soil organic C (SOC) pool have contributed 78±12 Pg of C to the atmosphere. Some cultivated soils have lost one-half to two-thirds of the original SOC pool with a cumulative loss of 30–40 Mg C/ha (Mg=megagram=106 G=1 ton). The depletion of soil C is accentuated by soil degradation and exacerbated by land misuse and soil mismanagement. Thus, adoption of a restorative land use and recommended management practices (RMPs) on agricultural soils can reduce the rate of enrichment of atmospheric CO2 while having positive impacts on food security, agro-industries, water quality and the environment. A considerable part of the depleted SOC pool can be restored through conversion of marginal lands into restorative land uses, adoption of conservation tillage with cover crops and crop residue mulch, nutrient cycling including the use of compost and manure, and other systems of sustainable management of soil and water resources. Measured rates of soil C sequestration through adoption of RMPs range from 50 to 1000 kg/ha/year. The global potential of SOC sequestration through these practices is 0.9±0.3 Pg C/year, which may offset one-fourth to one-third of the annual increase in atmospheric CO2 estimated at 3.3 Pg C/year. The cumulative potential of soil C sequestration over 25–50 years is 30–60 Pg. The soil C sequestration is a truly win–win strategy. It restores degraded soils, enhances biomass production, purifies surface and ground waters, and reduces the rate of enrichment of atmospheric CO2 by offsetting emissions due to fossil fuel.
ABSTRACT: Recent rapid changes in the Earth's climate have altered ecological systems around the globe. Global warming has been linked to changes in physiology, phenology, species distributions, interspecific interactions, and disturbance regimes. Projected future climate change will undoubtedly result in even more dramatic shifts in the states of many ecosystems. These shifts will provide one of the largest challenges to natural resource managers and conservation planners. Managing natural resources and ecosystems in the face of uncertain climate requires new approaches. Here, the many adaptation strategies that have been proposed for managing natural systems in a changing climate are reviewed. Most of the recommended approaches are general principles and many are tools that managers are already using. What is new is a turning toward a more agile management perspective. To address climate change, managers will need to act over different spatial and temporal scales. The focus of restoration will need to shift from historic species assemblages to potential future ecosystem services. Active adaptive management based on potential future climate impact scenarios will need to be a part of everyday operations. And triage will likely become a critical option. Although many concepts and tools for addressing climate change have been proposed, key pieces of information are still missing. To successfully manage for climate change, a better understanding will be needed of which species and systems will likely be most affected by climate change, how to preserve and enhance the evolutionary capacity of species, how to implement effective adaptive management in new systems, and perhaps most importantly, in which situations and systems will the general adaptation strategies that have been proposed work and how can they be effectively applied.
Malmsheimer, R. W., Heffernan, P., Brink, S., Crandall, D., Deneke, F., Galik, C., Gee, E., Helms, J. A., McClure, N., Mortimer, M., Ruddell, S., Smith, M., Stewart, J. B. (2008). Forest management solutions for mitigating climate change in the United States. Journal of Forestry 106 (3): 115-173
G. Marland, R.A. Pielke, Sr., M. Apps, R. Avissar, R. A. Betts, K.J. Davis, P.C. Frumhoff, S.T. Jackson, L.A. Joyce, P. Kauppi, J. Katzenberger, K. G. MacDicken, R. P. Neilson, J. O. Niles, D. S. Niyogi, R. J. Norby, N. Pena, N. Sampson, Y. Xue (2003). The climatic impacts of land surface change and carbon management, and the implications for climate-change mitigation policy. Climate Policy 3 (2): 149-157
ABSTRACT: Strategies to mitigate anthropogenic climate change recognize that carbon sequestration in the terrestrial biosphere can reduce the build-up of carbon dioxide in the Earth’s atmosphere. However, climate mitigation policies do not generally incorporate the effects of these changes in the land surface on the surface albedo, the fluxes of sensible and latent heat to the atmosphere, and the distribution of energy within the climate system. Changes in these components of the surface energy budget can affect the local, regional, and global climate. Given the goal of mitigating climate change, it is important to consider all of the effects of changes in terrestrial vegetation and to work toward a better understanding of the full climate system. Acknowledging the importance of land surface change as a component of climate change makes it more challenging to create a system of credits and debits wherein emission or sequestration of carbon in the biosphere is equated with emission of carbon from fossil fuels. Recognition of the complexity of human-caused changes in climate does not, however, weaken the importance of actions that would seek to minimize our disturbance of the Earth’s environmental system and that would reduce societal and ecological vulnerability to environmental change and variability.
ABSTRACT: The possibility of encouraging the growth of forests as a means of sequestering carbon dioxide has received considerable attention, partly because of evidence that this can be a relatively inexpensive means of combating climate change. But how sensitive are such estimates to specific conditions? We examine the sensitivity of carbon sequestration costs to changes in critical factors, including the nature of management and deforestation regimes, silvicultural species, relative prices, and discount rates.
ABSTRACT: A slew of new reports calls for federal agencies to address climate change through adaptive management of public lands and waters.
ABSTRACT: During the past 50 years, biogeochemistry has emerged as the premier scientific discipline to examine human impacts on the global environment. Important advances have derived from the synthesis of biogeochemical cycles at the global level, from the recognition that biochemical stoichiometry constrains the composition of living tissue, and from large-scale experiments that address the response of whole ecosystems to human impact. Future work will further pursue these avenues, with frequent use of modern, molecular methods to ascertain the role of individual species and species diversity in ecosystem function. Biogeochemists will increasingly need to translate the important results of their work to help formulate effective environmental policy.
P. Smith, D. S. Powlson, J. U. Smith, P. Falloon, K. Coleman (2000). Meeting Europe's climate change commitments: quantitative estimates of the potential for carbon mitigation by agriculture. Global Change Biology 6 (5): 525-539
ABSTRACT: Under the Kyoto Protocol, the European Union is committed to a reduction in CO2 emissions to 92% of baseline (1990) levels during the first commitment period (2008–2012). The Kyoto Protocol allows carbon emissions to be offset by demonstrable removal of carbon from the atmosphere. Thus, land-use/land-management change and forestry activities that are shown to reduce atmospheric CO2 levels can be included in the Kyoto targets. These activities include afforestation, reforestation and deforestation (article 3.3 of the Kyoto Protocol) and the improved management of agricultural soils (article 3.4). In this paper, we estimate the carbon mitigation potential of various agricultural land-management strategies and examine the consequences of European policy options on carbon mitigation potential, by examining combinations of changes in agricultural land-use/land-management.
We show that no single land-management change in isolation can mitigate all of the carbon needed to meet Europe's climate change commitments, but integrated combinations of land-management strategies show considerable potential for carbon mitigation. Three of the combined scenarios, one of which is an optimal realistic scenario, are by themselves able to meet Europe's emission limitation or reduction commitments.
Through combined land-management scenarios, we show that the most important resource for carbon mitigation in agriculture is the surplus arable land. We conclude that in order to fully exploit the potential of arable land for carbon mitigation, policies will need to be implemented to allow surplus arable land to be put into alternative long-term land-use.
Of all options examined, bioenergy crops show the greatest potential for carbon mitigation. Bioenergy crop production also shows an indefinite mitigation potential compared to other options where the mitigation potential is finite. We suggest that in order to exploit fully the bioenergy option, the infrastructure for bioenergy production needs to be significantly enhanced before the beginning of the first Kyoto commitment period in 2008.
It is not expected that Europe will attempt to meet its climate change commitments solely through changes in agricultural land-use. A reduction in CO2 -carbon emissions will be key to meeting Europe's Kyoto targets, and forestry activities (Kyoto Article 3.3) will play a major role. In this study, however, we demonstrate the considerable potential of changes in agricultural land-use and -management (Kyoto Article 3.4) for carbon mitigation and highlight the policies needed to promote these agricultural activities. As all sources of carbon mitigation will be important in meeting Europe's climate change commitments, agricultural carbon mitigation options should be taken very seriously.
FIRST PARAGRAPH: Science has established conclusively that concentrations of greenhouse gases (GHG) in the Earth’s atmosphere have been rising rapidly since the Industrial Revolution (e.g., see IPCC, 1996). While these increasing concentrations are associated primarily with fossil fuel consumption, a significant share (estimated in the range of 12 to 42 per cent) is believed to be caused by changes in land use, including deforestation and the expansion of agriculture (Watson et al., 2000, p. 5). While the consequences of increasing atmospheric GHG concentrations remains the subject of intensive scientific study and debate (see the US National Assessment [US Global Change Research Program, 2000] and [IPPC, 1996, 2001] for current literature reviews), there is growing national and international momentum to implement policies to reduce GHG emissions. The most obvious -- but not necessarily least costly -- way to do that is to reduce fossil fuel consumption. However GHGs can also be removed from the atmosphere by reversing some of the processes associated with land use changes.
ABSTRACT: Soil science must play a crucial role in meeting present and emerging societal needs of the 21st century and beyond for a population expected to stabilize around 10 billion and having increased aspirations for a healthy diet and a rise in the standards of living. In addition to advancing food security by eliminating hunger and malnutrition, soil resources must be managed regarding numerous other global needs through interdisciplinary collaborations. Some of which are to mitigate global warming; to improve quantity and quality of freshwater resources; to enhance biodiversity; to minimize desertification; serve as a repository of waste; an archive of human and planetary history; meet growing energy demands; develop strategies of sustainable management of urban ecosystems; alleviate poverty of agricultural communities as an engine of economic development; and fulfill aspirations of rapidly urbanizing and industrializing societies. In addition to food and ecosystem services, bio-industries (e.g., plastics, solvents, paints, adhesives, pharmaceuticals and chemicals) through plant-based compounds (carbohydrates, proteins, and oils) and energy plantations (bioethanol and biodiesel) can revolutionize agriculture. These diverse and complex demands on soil resources necessitate a shift in strategic thinking and conceptualizing sustainable management of soil resources in agroecosystems to provide all ecosystem services while also meeting the needs for food, feed, fiber, and fuel by developing multifunctional production systems. There is a strong need to broaden the scope of soil science to effectively address ever changing societal needs. To do this, soil scientists must rally with allied sciences including hydrology, climatology, geology, ecology, biology, physical sciences (chemistry, physics), and engineering. Use of nanotechnology, biotechnology, and information technology can play an important role in addressing emerging global issues. Pursuit of sustainability, being a moral/ethical and political challenge, must be addressed in cooperation with economists and political scientists. Soil scientists must work in cooperation with industrial ecologists and urban planners toward sustainable development and management of soils in urban and industrial ecosystems. More than half of the world's population (3.3 billion) live in towns and cities, and the number of urban dwellers is expected to increase to 5 billion by 2030. Thus, the study of urban soils for industrial use, human habitation, recreation, infrastructure forestry, and urban agriculture is a high priority. Soil scientists must nurture symbiotic/synergistic relations with numerous stake holders including land managers, energy companies and carbon traders, urban planners, waste disposal organizations, and conservators of natural resources. Trading of C credits in a trillion-dollar market by 2020 must be made accessible to land managers, especially the resource-poor farmers in developing countries. Soil science curricula, at undergraduate and graduate levels, must be revisited to provide the needed background in all basic and applied sciences with focus on globalization. We must raise the profile of soil science profession and position students in the competitive world of ever flattening Earth.
ABSTRACT: 1 Biological carbon sinks develop in mature ecosystems that have high carbon storage when these systems are stimulated to increase productivity, so that carbon gains by photosynthesis run ahead of carbon losses by heterotrophic respiration, and the stocks of carbon therefore increase. This stimulation may occur through elevated CO2 concentration, nitrogen deposition or by changes in climate.
2 Sinks also occur during the 'building' phase of high carbon ecosystems, for example following establishment of forests by planting.
3 New methods have been developed to identify biological carbon sinks: ground based measurements using eddy covariance coupled with inventory methods, atmospheric methods which rely on repeated measurement of carbon dioxide concentrations in a global network, and mathematical models which simulate the processes of production, storage and decomposition of organic matter. There is broad agreement among the results from these methods: carbon sinks are currently found in tropical, temperate and boreal forests as well as the ocean.
4 However, on a global scale the effect of the terrestrial sinks (absorbing 2–3 billion tonnes of carbon per year) is largely offset by deforestation in the tropics (losing 1–2 billion tonnes of carbon per year).
5 The Kyoto Protocol provides incentives for the establishment of sinks. Unfortunately, it does not provide an incentive to protect existing mature ecosystems which constitute both stocks of carbon and (currently) carbon sinks.
6 Incentives would be enhanced, if protection and nature conservation were to be part of any international agreement relating to carbon sinks.
ABSTRACT: The continued accumulation of greenhouse gases in the atmosphere is expected to severely impact the earth's natural resources and agriculture. Greenhouse gas emissions from the developing world are rising faster than those from other countries, and many studies have noted that it would not be possible to stabilize climate change without reducing the growth of these emissions. Can this be achieved without affecting economic growth and social fabric in these countries? Mitigation studies indicate that if energy efficiency and forestry options are implemented judiciously, emissions can be reduced at a negative cost without affecting economic growth. The studies also suggest that this would increase significantly the worldwide demand for natural gas and renewable technologies. Country studies show that the aggregate mitigation potential in the forestry sector is higher, and the costs per tonne of carbon are lower, than reported earlier by global studies. Barriers to the implementation of energy and forestry options need to be explicitly taken into consideration because these may change the priority of options and the choice of policy measures.
ABSTRACT: Forests currently absorb billions of tons of CO2 globally every year, an economic subsidy worth hundreds of billions of dollars if an equivalent sink had to be created in other ways. Concerns about the permanency of forest carbon stocks, difficulties in quantifying stock changes, and the threat of environmental and socioeconomic impacts of large-scale reforestation programs have limited the uptake of forestry activities in climate policies. With political will and the involvement of tropical regions, forests can contribute to climate change protection through carbon sequestration as well as offering economic, environmental, and sociocultural benefits. A key opportunity in tropical regions is the reduction of carbon emissions from deforestation and degradation.
ABSTRACT: Adaptation in forestry is sustainable forest management that includes a climate change focus. Climate change over the next 100 years is expected to have significant impacts on forest ecosystems. The forestry community needs to evaluate the long-term effects of climate change on forests and determine what the community might do now and in the future to respond to this threat. Management can influence the timing and direction of forest adaptation at selected locations, but in many situations society will have to adjust to however forests adapt. Adapting to climate change in the face of the uncertain timing of impacts means we must have a suite of readily available options. A high priority will be coping with and adapting to forest disturbance while maintaining the genetic diversity and resilience of forest ecosystems. A framework for facilitating adaptation in forestry is discussed and a review of adaptive actions presented.
ABSTRACT: One way of mitigating global climate change is protecting and enhancing biosphere carbon stocks. The success of mitigation initiatives depends on the long-term net balance between carbon gains and losses. The biodiversity of ecological communities, including composition and variability of traits of plants and soil organisms, can alter this balance in several ways. This influence can be direct, through determining the magnitude, turnover rate, and longevity of carbon stocks in soil and vegetation. It can also be indirect through influencing the value and therefore the protection that societies give to ecosystems and their carbon stocks. Biodiversity of forested ecosystems has important consequences for long-term carbon storage, and thus warrants incorporation into the design, implementation, and regulatory framework of mitigation initiatives.
ABSTRACT: International efforts to mitigate human-caused changes in the Earth's climate are considering a system of incentives (debits and credits) that would encourage specific changes in land use that can help to reduce the atmospheric concentration of carbon dioxide. The two primary land-based activities that would help to minimize atmospheric carbon dioxide are carbon storage in the terrestrial biosphere and the efficient substitution of biomass fuels and bio-based products for fossil fuels and energy-intensive products. These two activities have very different land requirements and different implications for the preservation of biodiversity and the maintenance of other ecosystem services. Carbon sequestration in living forests can be pursued on lands with low productivity, i.e. on lands that are least suitable for agriculture or intensive forestry, and are compatible with the preservation of biodiversity over large areas. In contrast, intensive harvest-and-use systems for biomass fuels and products generally need more productive land to be economically viable. Intensive harvest-and-use systems may compete with agriculture or they may shift intensive land uses onto the less productive lands that currently harbor most of the Earth's biodiversity. Win–win solutions for carbon dioxide control and biodiversity are possible, but careful evaluation and planning are needed to avoid practices that reduce biodiversity with little net decrease in atmospheric carbon dioxide. Planning is more complex on a politically subdivided Earth where issues of local interest, national sovereignty, and equity come into play.
ABSTRACT: Forests are important in the global carbon cycle, forming a major sink for carbon. Deforestation is a significant source of carbon dioxide emitted to the atmosphere. There is some scope to enhance natural carbon sinks, and therefore reduce net emissions of greenhouse gases, through afforestation and conservation of existing forests. Such initiatives may be implemented to “offset” emissions of greenhouse gases from other sources. This may be undertaken by private companies, or by governments as part of bilateral agreements or multilateral arrangements. International carbon offsets may be cost effective in terms of reduction of carbon emissions achieved, and may also be one way to mobilise private capital to fund forest conservation. It is argued here that theoretically the international offset of emissions may lead to a resource saving, and that forest conservation, as opposed to afforestation, may bring about many other benefits. However, such international contracts are unlikely to be feasible or make a major contribution to the control of greenhouse gases. The reasons for this are monitoring, enforcement and scientific uncertainties, and the implicit change in property rights involved in “selling” carbon sequestration rights.
ABSTRACT: Carbon capture and storage (or sequestration) is receiving increasing attention as one tool for reducing carbon dioxide concentrations in the atmosphere. In his Perspective, Lackner discusses the advantages and disadvantages of different methods of carbon sequestration. He advises against sequestration in environmentally active carbon pools such as the oceans, because it may merely trade one environmental problem for another. Better sequestration options include underground injection and (possibly underground) neutralization. Taking into account carbon capture, transport, and storage, the author concludes that in the short and medium term, sequestration would almost certainly be cheaper than a full transition to nuclear, wind, or solar energy.
McGrail, B. P., H. T. Schaef, A. M. Ho, Y.-J. Chien, J. J. Dooley, C. L. Davidson (2006). Potential for carbon dioxide sequestration in flood basalts. Journal of Geophysical Research 111 (B12201): doi:10.1029/2005JB004169
ABSTRACT: Flood basalts are a potentially important host medium for geologic sequestration of anthropogenic CO2 . Most lava flows have flow tops that are porous and permeable and have enormous capacity for storage of CO2 . Interbedded sediment layers and dense low-permeability basalt rock overlying sequential flows may act as effective seals allowing time for mineralization reactions to occur. Laboratory experiments confirm relatively rapid chemical reaction of CO2 -saturated pore water with basalts to form stable carbonate minerals. Calculations suggest a sufficiently short time frame for onset of carbonate precipitation after CO2 injection that verification of in situ mineralization rates appears feasible in field pilot studies. If proven viable, major flood basalts in the United States and India would provide significant additional CO2 storage capacity and additional geologic sequestration options in certain regions where more conventional storage options are limited.
ABSTRACT: Greenhouse gas mitigation possibilities in the agricultural and forest sector represent a complex system of interlinked strategies. To assess their true economic implementation potential, major mitigation strategies are simultaneously examined with a U.S. agricultural sector model over a large range of hypothetical carbon prices. Soil carbon sequestration through reduced tillage appears most attractive for relatively low carbon prices. Afforestation and biofuel generation, however, dominate at higher price levels. For politically feasible prices, the competitive economic contribution of all major strategies is greatly below their technical potential. However, positive environmental and social coeffects may increase the importance of agricultural mitigation policies.
ABSTRACT: Carbon sequestration is a temporal process in which carbon is continuously being stored/released over a period of time. Different methods of carbon accounting can be used to account for this temporal nature including annual average carbon, annualized carbon, and ton-year carbon. In this paper, starting by exposing the underlying connections among these methods, we examine how the comparisons of sequestration projects are affected by these methods and the major factors affecting them. We explore the empirical implications on carbon sequestration policies by applying these accounting methods to the Upper Mississippi River Basin, a large and important agriculture area in the US. We found that the differences are significant in terms of the location of land that might be chosen and the distribution of carbon sequestration over the area, although the total amount of carbon sequestered does not differ considerably across programs that use different accounting methods or different values of the major factors.
FIRST PARAGRAPH: The popular dictum is “Think globally, act locally.” We might want to modify it somewhat to “Protect globally, recycle locally.” Poll after poll indicates that citizens connect recycling with saving the environment — by saving energy and water resources, reducing timber harvests and keeping recoverable materials out of landfills. But there may be another, larger benefit, one that will affect not just the environment in the United States, but that of all countries.
Recent research conducted by the Forest Products Laboratory (Madison, Wisconsin) found that 10 to 20 percent of the U.S. carbon reduction goal could be met through a range of scenarios for paper and wood recycling. More aggressive paper and wood recycling — as well as composting, source reducing and recycling other recoverable materials — can provide even more dramatic decreases.
N. W. Arnell, M. G. R. Cannell, M. Hulme, R. S. Kovats, J. F. B. Mitchell, R. J. Nicholls, M. L. Parry, M. T. J. Livermore, A. White (2002). The consequences of CO2 stabilisation for the impacts of climate change. Climatic Change 53 (4): 413-446
ABSTRACT: This paper reports the main results of an assessment of the global-scale implications of the stabilisation of atmospheric CO2 concentrations at 750 ppm (by 2250) and 550 ppm (by 2150), in relationto a scenario of unmitigated emissions. The climate change scenarios were derived from simulation experiments conducted with the HadCM2 global climate model and forced with the IPCC IS92a, S750 and S550 emissions scenarios. The simulated changes in climate were applied to an observed global baseline climatology, and applied with impacts models to estimate impacts on natural vegetation, water resources, coastal flood risk and wetland loss, crop yield and food security, and malaria. The studies used a single set of population and socio-economic scenarios about the future that are similar to those adopted in the IS92a emissions scenario.An emissions pathway which stabilises CO2 concentrations at 750 ppmby the 2230s delays the 2050 temperature increase under unmitigated emissions by around 50 years. The loss of tropical forest and grassland which occurs by the 2050s under unmitigated emissions is delayed to the 22nd century, and the switch from carbon sink to carbon source is delayed from the 2050s to the 2170s. Coastal wetland loss is slowed. Stabilisation at 750 ppm generally has relatively little effect on the impacts of climate change on water resource stress, and populations at risk of hunger or falciparum malaria until the 2080s.A pathway which stabilises CO2 concentrations at 550 ppm by the 2170s delays the 2050 temperature increase under unmitigated emissions by around 100 years. There is no substantial loss of tropical forest or grassland, even by the 2230s, although the terrestrial carbon store ceases to act as a net carbon sink by around 2170 (this time because the vegetation has reached a new equilibrium with the atmosphere). Coastal wetland loss is slowed considerably, and the increase in coastal flood risk is considerably lower than under unmitigated emissions. CO2 stabilisation at 550 ppm reduces substantially water resource stress, relative to unmitigated emissions, but has relatively little impact on populations at risk of falciparum malaria, and may even cause more people to be at risk of hunger. While this study shows that mitigation avoids many impacts, particularly in the longer-term (beyond the 2080s), stabilisation at 550 ppm appears to be necessary to avoid or significantly reduce most of the projected impacts in the unmitigated case.
Keith, H., Mackey, B. G., Lindenmayer, D. B. (2009). Re-evaluation of forest biomass carbon stocks and lessons from the world's most carbon-dense forests. Proceedings of the National Academy of Sciences 106 (28): 11635-11640
ABSTRACT: From analysis of published global site biomass data (n = 136) from primary forests, we discovered (i) the world's highest known total biomass carbon density (living plus dead) of 1,867 tonnes carbon per ha (average value from 13 sites) occurs in Australian temperate moistEucalyptus regnans forests, and (ii) average values of the global site biomass data were higher for sampled temperate moist forests (n = 44) than for sampled tropical (n = 36) and boreal (n = 52) forests (n is number of sites per forest biome). Spatially averaged Intergovernmental Panel on Climate Change biome default values are lower than our average site values for temperate moist forests, because the temperate biome contains a diversity of forest ecosystem types that support a range of mature carbon stocks or have a long land-use history with reduced carbon stocks. We describe a framework for identifying forests important for carbon storage based on the factors that account for high biomass carbon densities, including (i) relatively cool temperatures and moderately high precipitation producing rates of fast growth but slow decomposition, and (ii) older forests that are often multiaged and multilayered and have experienced minimal human disturbance. Our results are relevant to negotiations under the United Nations Framework Convention on Climate Change regarding forest conservation, management, and restoration. Conserving forests with large stocks of biomass from deforestation and degradation avoids significant carbon emissions to the atmosphere, irrespective of the source country, and should be among allowable mitigation activities. Similarly, management that allows restoration of a forest's carbon sequestration potential also should be recognized.