Recently the term natural has come under some scrutiny. I would like to address some of the concerns expressed by Shrader-Frechette and McCoy in a paper that was excerpted in the fall 1995 issue of the Natural Areas Report. 1
For the purpose of defining natural areas, it has become increasingly acceptable to include the thousands of years of Native American participation in nature as part of the natural condition.3 Much of their influence was through predation and the use of fire, in some ways similar to the effects of wolves or lightning. In presettlement times Native Americans lived among large herds of bison, flocks of passenger pigeons, mountain lions, black-footed ferrets, and grizzlies that moved across an unfragmented continent of wild grasslands and forests. This world is gone.
Humans are obviously part of nature. However, we are busily reshaping and often degrading the world in ways that are orders of magnitude more severe than Native American influences. Human involvement in nature represents a complex continuum, specific to time and place. Natural areas are as close to one end of that continuum as geography and history allow.
In western North America there are still a few places with most or all of their native species, with relatively intact ecological and evolutionary processes, and an absence of roads, logging, buildings and other obvious human influences. In northern Alaska, at one extreme, grizzlies still wander among vast herds of caribou in a seemingly endless, mostly uninhabited landscape. However, in the central United States most tallgrass prairie has been lost to the plow. The few unplowed prairie remnants are small and missing the migrations of bison and predation of wolves. Yet these fragments are the best examples we can find of a once extensive natural landscape. They are of value for the myriad plant and animal species they protect and for what they can teach us about the ecological functioning of these complex grasslands. Perhaps more importantly a tallgrass prairie natural area is a part of our vanishing natural heritage.
The new paradigm, variously called the non-equilibrium or hierarchical patch dynamics paradigm,5 recognizes explicitly what many ecologists have known for decades: that many different kinds of change are operative in ecological systems over a great range of temporal and spacial scales.6 Populations often vary unpredictably; falling trees create gaps in the forest; fires, windstorms and insect epidemics leave a shifting mosaic of patches in forested landscapes; and ice ages cause great geographic movements in vegetation. Disturbance and change have become the new ecological grail.7
Yet despite ecological disturbance and change, many types of forest and grassland have persisted regionally for thousands of years.8 These biotic communities and ecosystems have been named and classified. 9 At high elevations in the Rocky Mountains, spruce-fir forests, often with an understory of whortleberry, are a familiar and persistent feature in the landscape. Martens have hunted squirrels in the deep winter snows of these forests for a time-span longer than the existence of the human species. The perception of change is relative to the time and spatial scales of the perceiver.
Although the magnitude and timing of ecological change in a specific location is unpredictable, the principal patterns of change are usually well known. For example, in many western ponderosa pine forests we know that understory fires were very common in presettlement times, occurring roughly every five to thirty years depending on region. We know this from examining tree rings and aging firescars in trees as old as 500 years. These fires burned the understory vegetation, killed many small trees, and created open park-like stands of large pines. The science of dendrochronology is beginning to unravel some of the presettlement fire patterns of forest ecosystems.10
The idea of ecological change and variability does not invalidate our knowledge of what is natural, it merely helps refine it. Even our current knowledge of climatic variability's great influence on ecosystems,11 helps focus our understanding of what is natural on the continuity of ecological processes rather than on discrete places or moments in time. Incorporating ecological change into land management decisions, and especially natural areas selection, often requires thinking at larger spatial and temporal scales.12 Natural areas for many ecosystem types should be large enough to maintain ecological processes such as fire and to represent the pattern of disturbance patches that form natural landscape mosaics.13
The forms of disturbance and change operative in natural ecological systems are part of the four billion year old evolutionary processes that have molded life on earth. The new ecological paradigm has revealed that natural areas may not remain natural unless they are large enough to encompass the evolutionary and ecological processes that species and ecosystems depend upon.
Without putting too fine a point on it, most ecologists understand an ecosystem to include the plants, animals, land, water, and air and the processes that interconnect them in a given place. Some scientists focus more on the flow of energy and nutrients within ecosystems and others on the interactions of species. Different functional definitions are often applied to the same phenomenon. The difficulties in precisely defining ecosystems or biotic communities in no way invalidate the idea that some places on earth remain in a more natural condition than others.
There is still an enormous amount we don't know and may never know about the complex functioning of life on earth. Our very uncertainty should be humbling enough for us to realize that, whatever we call them and however much they vary, good examples of the earth's remaining relatively natural assemblages of species, landforms, geologies, and climates should be protected before they are lost. Although not exemplary for defining natural, our impacted landscapes need not always be off limits to natural area selection. Ecological restoration may offer our best opportunity for representing some ecosystem types in natural areas.
Natural areas provide a useful contrast to manipulated lands around them. They are necessary benchmarks for ecosystem management.17 For instance, if we need to determine how much soil erosion is attributable to livestock grazing on a fescue grassland, it helps to have for comparison an ecologically similar control area of fescue grassland that isn't grazed.
A representative natural areas system is a significant component of any regional strategy to protect biodiversity.18 If examples of most ecosystem types are protected in natural areas, then populations of the majority of plant and animal species will also likely be protected.
Natural areas are particularly useful in enhancing the scientific understanding of ecosystems, biodiversity, and sustainability. The decision to put value in biological diversity and natural processes certainly is a choice of society, though some would say not to make that choice would be collective suicide. However, the decision to use natural areas to test our understanding of the significance of those values is based in science. Natural areas provide some of the best remaining examples of the diversity of natural ecosystems, many of which are disappearing from the earth.
Natural areas provide demonstrations of naturalness, more useful than any syntactic debate, particularly in a world of change and uncertainty. As the earth becomes increasingly transformed by industrial development and expanding human populations, it is easy to predict that the current importance of natural areas will be overshadowed by their value in the future.19
1. Shrader-Frechette, K.S. and E.D. McCoy. 1995. Natural landscapes, natural communities, and natural ecosystems. Forest and Conservation History 39:138-142.
2. Maser, C. 1990. On the "naturalness" of natural areas: A perspective for the future. Natural Areas Journal 10:129-133.
3. Bonnicksen, T.M. and E.C. Stone. 1985. Restoring naturalness to National Parks. Environmental Management 9:479-486.
4. Pickett, S.T.A. and P.S. White, ed. 1985. The Ecology of Natural Disturbance and Patch Dynamics. Academic Press, Orlando, FL.
5. Wu, J. and O.L. Loucks. 1995. From balance of nature to hierarchical patch dynamics: A paradigm shift in ecology. The Quarterly Review of Biology 70:439-466.
6. Barbour, M.G. 1995. Ecological fragmentation in the fifties. In: W. Cronon, ed. Uncommon Ground, Toward Reinventing Nature. W.W. Norton and Co., New York, NY.
7. Worster, D. 1993. The Wealth of Nature: Environmental History and the Ecological Imagination, Oxford University Press, New York, NY.
8. Daubenmire, R. 1978. Plant Geography. Academic Press, New York, NY.
9. Alexander, R.R. 1985. Major habitat types, community types, and plant communities in the Rocky Mountains. USDA Forest Service. General Technical Report RM-123. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO.
10. Brown, J.K. et al. 1995. Proceedings: Symposium on Fire in Wilderness and Park Management. General Technical Report INT-320. USDA Forest Service, Intermountain Research Station, Ogden, UT.
11. Sprugel, D.G. 1991. Disturbance, equilibrium, and environmental variability: What is `natural' vegetation in a changing environment? Biological Conservation 58:1-18.
12. Pickett, S. et al. 1992. The new paradigm in ecology: implications for conservation biology above the species level. In: Fiedler, P.L. et al. Conservation Biology. Chapman and Hall, New York, NY.
13. Noss, R.F. 1987. Protecting natural areas in fragmented landscapes. Natural Areas Journal 7:2-13.
14. Soule, M.E. and G. Lease, ed. 1995. Reinventing Nature? Responses to Postmodern Deconstruction. Island Press, Washington, D.C.
15. Rolston, H. 1994. Conserving Natural Values.
16. Moir, W.H. 1972. Natural Areas. Science 177:396-400.
17. Ryan, M.G. etal. 1994. Research Natural Areas. General Technical Report RM-251, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO.
18. Margules, C.R. 1988. Selecting networks of reserves to maximize biological diversity. Biological Conservation 43:63-76.
19. Wilson, E.O., ed. 1988. Biodiversity. National Academy Press, Washington, D.C.