Climate Change and...
Effects of Climate Change
- Climate Variability
- Climate Models
Effects of Climate Change
ABSTRACT: The foliar compliment of evergreen conifer trees is dependent on the crown ratio and foliar longevity. Variation in foliage longevity is one of the important traits that often favours the genusPinus over its competitors. Healthy lodgepole pine trees throughout British Columbia, Canada typically retain needles for 4 to 5 years. Foliar diseases have a profound influence on foliar longevity and crown ratio, and lodgepole pine is susceptible to a large suite of foliar pathogens. We assessed the foliar longevity, live crown percent and mortality of lodgepole pine trees at 25 lodgepole pine provenance test sites in central BC, and correlated these values with changes in climate at each site between the decade of the 1920s and the 1990s. We found strong relationships between increases in August minimum temperatures and live crown percent (R = -0.75) and mortality (R = 0.75). Sites in Region 7 of the trial (Robson Valley) consistently have the least foliage and have consistently experienced the greatest increases in August minimum temperature and July precipitation, and the greatest decreases in May maximum temperature. Region 9 (Nechako Plateau) sites consistently have the most foliage and have consistently experienced the least change in August minimum temperature, July precipitation, and greatest increases in May maximum temperature. Future changes in climate in conjunction with foliar pathogens could have profound effects on the health of lodgepole pine in BC.
Dukes, Jeffrey S., Pontius, Jennifer, Orwig, David, Garnas, Jeffrey R., Rodgers, Vikki L., Brazee, Nicholas, Cooke, Barry, Theoharides, Kathleen A., Stange, Erik E., Harrington, Robin, Ehrenfeld, Joan, Gurevitch, Jessica, Lerdau, Manuel, Stinson, Kristina, Wick, Robert, Ayres, Matthew (2009). Responses of insect pests, pathogens, and invasive plant species to climate change in the forests of northeastern North America : what can we predict?. Canadian Journal of Forest Research 39 (2): 231-248
ABSTRACT: Climate models project that by 2100, the northeastern US and eastern Canada will warm by approximately 3–5 °C, with increased winter precipitation. These changes will affect trees directly and also indirectly through effects on “nuisance” species, such as insect pests, pathogens, and invasive plants. We review how basic ecological principles can be used to predict nuisance species’ responses to climate change and how this is likely to impact northeastern forests. We then examine in detail the potential responses of two pest species (hemlock woolly adelgid (Adelges tsugae Annand) and forest tent caterpillar (Malacosoma disstria Hubner)), two pathogens (armillaria root rot (Armillaria spp.) and beech bark disease (Cryptococcus fagisuga Lind. +Neonectria spp.)), and two invasive plant species (glossy buckthorn (Frangula alnus Mill.) and oriental bittersweet (Celastrus orbiculatus Thunb.)). Several of these species are likely to have stronger or more widespread effects on forest composition and structure under the projected climate. However, uncertainty pervades our predictions because we lack adequate data on the species and because some species depend on complex, incompletely understood, unstable relationships. While targeted research will increase our confidence in making predictions, some uncertainty will always persist. Therefore, we encourage policies that allow for this uncertainty by considering a wide range of possible scenarios.
ABSTRACT: The circum-polar boreal forest has played an important role in the wealth of northern nations since the 15th century. Its natural resources spurred strategic geopolitical developments beginning in the 16th century but intense development of the boreal forest is largely limited to the 20th century. Insects cause considerable loss of wood that has an adverse effect on the balance of carbon sequestered by forests. Current understanding of processes that lead to stand-replacing outbreaks in three insect species is reviewed in this paper. Many of these processes depend on climate either directly, such as reduced survival with extreme weather events, or indirectly, mainly through effects on the host trees. In the boreal zone of Canada, pest-caused timber losses may be as much as 1.3–2.0 times the mean annual depletions due to fires. Pests are thus major, but consistently overlooked forest ecosystem components that have manifold consequences to the structure and functions of future forests. Global change will have demonstrable changes in the frequency and intensity of pest outbreaks, particularly at the margins of host ranges. The consequent shunting of carbon back to the atmosphere rather than to sequestration in forests as biomass is thought to have positive feedback to global warming. Whereas significant progress has been made in developing carbon budget models for the boreal forests of Canada, enormous problems remain in incorporating pest effects in these models. These problems have their origins in the nature of interactions among pests with forest productivity, and problems with scaling. The common problems of verification and validation of model results are particularly troublesome in projecting future forest productivity. The interaction of insects with fires must be accounted for if realistic carbon sequestration forecasts in a warming climate are to be made. These problems make assessments of mitigation and adaptation of pest management alternatives difficult to evaluate at present. Nevertheless, the impacts of stand-replacing insect population outbreaks is important in formulating future resource management policy.
W. A. Kurz, C. C. Dymond, G. Stinson, G. J. Rampley, E. T. Neilson, A. L. Carroll, T. Ebata, L. Safranyik (2008). Mountain pine beetle and forest carbon feedback to climate change. Nature 452 (24 April): 987-990
ABSTRACT: The mountain pine beetle (Dendroctonus ponderosae Hopkins, Coleoptera: Curculionidae, Scolytinae) is a native insect of the pine forests of western North America, and its populations periodically erupt into large-scale outbreaks1, 2, 3 . During outbreaks, the resulting widespread tree mortality reduces forest carbon uptake and increases future emissions from the decay of killed trees. The impacts of insects on forest carbon dynamics, however, are generally ignored in large-scale modelling analyses. The current outbreak in British Columbia, Canada, is an order of magnitude larger in area and severity than all previous recorded outbreaks4 . Here we estimate that the cumulative impact of the beetle outbreak in the affected region during 2000–2020 will be 270 megatonnes (Mt) carbon (or 36 g carbon m-2 yr-1 on average over 374,000 km2 of forest). This impact converted the forest from a small net carbon sink to a large net carbon source both during and immediately after the outbreak. In the worst year, the impacts resulting from the beetle outbreak in British Columbia were equivalent to 75% of the average annual direct forest fire emissions from all of Canada during 1959–1999. The resulting reduction in net primary production was of similar magnitude to increases observed during the 1980s and 1990s as a result of global change5 . Climate change has contributed to the unprecedented extent and severity of this outbreak6 . Insect outbreaks such as this represent an important mechanism by which climate change may undermine the ability of northern forests to take up and store atmospheric carbon, and such impacts should be accounted for in large-scale modelling analyses.
ABSTRACT: 1 One expected effect of global climate change on insect populations is a shift in geographical distributions toward higher latitudes and higher elevations. Southern pine beetleDendroctonus frontalis and mountain pine beetleDendroctonus ponderosae undergo regional outbreaks that result in large-scale disturbances to pine forests in the south-eastern and western United States, respectively.
2 Our objective was to investigate potential range shifts under climate change of outbreak areas for both bark beetle species and the areas of occurrence of the forest types susceptible to them.
3 To project range changes, we used discriminant function models that incorporated climatic variables. Models to project bark beetle ranges employed changed forest distributions as well as changes in climatic variables.
4 Projected outbreak areas for southern pine beetle increased with higher temperatures and generally shifted northward, as did the distributions of the southern pine forests.
5 Projected outbreak areas for mountain pine beetle decreased with increasing temperature and shifted toward higher elevation. That trend was mirrored in the projected distributions of pine forests in the region of the western U.S. encompassed by the study.
6 Projected outbreak areas for the two bark beetle species and the area of occurrence of western pine forests increased with more precipitation and decreased with less precipitation, whereas the area of occurrence of southern pine forests decreased slightly with increasing precipitation.
7 Predicted shifts of outbreak ranges for both bark beetle species followed general expectations for the effects of global climate change and reflected the underlying long-term distributional shifts of their host forests.
A. L. Carroll, S. W. Taylor, J. Régnière, L. Safranyik, T. L. Shore, J. E. Brooks, J. E. Stone (2003). Effects of climate change on range expansion by the Mountain Pine Beetle in British Columbia. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre Information Report BC-X-399: 223-232
ABSTRACT: The current latitudinal and elevational range of mountain pine beetle is not limited by available hosts. Instead, its potential to expand north and east has been restricted by climatic conditions unfavorable for brood development. We combined a model of the impact of climatic conditions on the establishment and persistence of mountain pine beetle populations with a spatially explicit, climate-driven simulation tool. Historic weather records were used to produce maps of the distribution of past climatically suitable habitats for mountain pine beetles in British Columbia. Overlays of annual mountain pine beetle occurrence on these maps were used to determine if the beetle has expanded its range in recent years due to changing climate. An examination of the distribution of climatically suitable habitats in 10-year increments derived from climate normals (1921-1950 to 1971-2000) clearly shows an increase in the range of benign habitats. Furthermore, an increase (at an increasing rate) in the number of infestations since 1970 in formerly climatically unsuitable habitats indicates that mountain pine beetle populations have expanded into these new areas. Given the rapid colonization by mountain pine beetles of former climatically unsuitable areas during the last several decades, continued warming in western North America associated with climate change will allow the beetle to further expand its range northward, eastward and toward
ABSTRACT: Forest insects and pathogens are the most pervasive and important agents of disturbance in North American forests, affecting an area almost 50 times larger than fire and with an economic impact nearly five times as great. The same attributes that result in an insect herbivore being termed a “pest” predispose it to disruption by climate change, particularly global warming. Although many pest species have co-evolved relationships with forest hosts that may or may not be harmful over the long term, the effects on these relationships may have disastrous consequences. We consider both the data and models necessary to evaluate the impacts of climate change, as well as the assessments that have been made to date. The results indicate that all aspects of insect outbreak behavior will intensify as the climate warms. This reinforces the need for more detailed monitoring and evaluations as climatic events unfold. Luckily, we are well placed to make rapid progress, using software tools, databases, and the models that are already available.