As large, intact ecosystems, frontier forests differ fundamentally from the fragmented or otherwise modified forests that dominate the landscape today. For one thing, frontier forests are large enough to provide a safe haven for all of their indigenous species. To ensure long-term survival, far-ranging animals such as grizzly bears, harpy eagles, and wolves need blocks of natural habitat thousands, if not tens of thousands, of square kilometers in size. [3], [4], [5].

Fragmented forests, on the other hand, are probably too small to support their full complement of species in the coming centuries. [6] Smaller tracts are also vulnerable to processes beyond their borders. In the United States, for example, the nests of songbirds in small forest patches are under heavy attack by cowbirds, bluejays, raccoons, and other animals that thrive along forest edges. [7] Many non-frontier forests also lack the natural features that native species rely on: In the U.S. Pacific Northwest, the spotted owl and marbled murrelet birds that depend on large, standing dead trees typically found in old-growth forests -- are threatened by logging of these ecosystems. [8]

Secure habitats for indigenous species, frontier forests are invaluable refuges for global biodiversity. Between 50 and 90 percent of all terrestrial species inhabit the world's forests, [9] and many of them are threatened by extinction, primarily because of habitat loss. (See Percent of the world's endangered animal species threatened by the loss of forest and other natural habitat.) By maintaining these last strongholds we protect the biodiversity within them and provide a source for recolonizing non-frontier and restored forests with native species. Beyond its obvious intrinsic value, biodiversity supplies humans with food, medicines, and many other staples needed to survive and make a living.

More than safe houses for genes and species under siege, frontier forests maintain complex and inimitable ecological communities and processes. Vast and undisturbed, they give free play to nature and to such natural events as wildfires and seed dispersal by large herbivores, both of which determine the composition and distribution of species. Such natural processes create unique habitats, including ancient stands of "old-growth" forest.

As large, intact ecosystems governed by nature, frontier forests provide baseline information on how such systems should work. Just as doctors use standard body temperature and blood pressure to determine health, ecologists study natural forests to evaluate the impact of different human interventions -- asking, for instance, how forest clearing might affect local rainfall patterns. The results help land managers find ways to lighten the human footprint in heavily used landscapes.

All forests help maintain the environmental conditions that make life possible, from regional hydrologic cycles to global climate. But huge frontiers are particularly important. Frontier forest ecosystems store tremendous amounts of carbon, for example -- approximately 433 billion tonnes, or more than all carbon that will be released from fossil fuel burning and cement manufacture over the next 69 years, at current global emission rates. [10] Without these forests, this carbon would go straight into the atmosphere as carbon dioxide, a powerful greenhouse gas.

Protecting and responsibly managing our last frontiers today will help countries avoid paying the high costs associated with massive forest loss and degradation. History abounds with examples of civilizations that foundered after deforestation led to soil erosion, river siltation, wood shortages, and other banes of agricultural and industrial productivity. These doomed civilizations include ancient societies in Mesopotamia, the Mediterranean, and Central America. [11]

More recently, erosion since 1950 due to deforestation is responsible for the loss of 580 million hectares of fertile land worldwide, an area bigger than all of Western Europe. [12] Loss of large forested watersheds is blamed for heavier flooding in India's Ganges Valley, and government losses of $1 billion a year in property damage. [13] By carefully managing what's left of the world's frontier forests, we can dramatically reduce such environmental side effects and costs.

Dwindling frontier forests are also home to many of the world's last indigenous cultures. About 50 million indigenous people live in tropical forests alone. [14] Amazonian forests house at least 400 indigenous groups -- 1 million people in all. [15]. Wiping out indigenous cultures by transforming forests is a moral crime. And when these cultures vanish, so does a gold mine of useful information about the natural world. A legacy inherited from our ancestors, Earth's last frontier forests may indeed be the most valuable gift we can leave for our children. Guardians of biodiversity, indigenous cultures, and ecological processes, frontiers also provide recreational and ecotourism opportunities. Because so many irreplaceable forests have already disappeared, the worth to future generations of those that remain is greater than ever.

Above and beyond practical considerations is the very real aesthetic and spiritual need just to know that remote and wild places remain on our crowded planet. One concrete reflection of this need is the considerable sum of money many people pay to visit such places. But even to many people who will never see them, wild plants and animals, along with the forests that house them, have an inalienable right to exist. Certainly, as Earth's most powerful species, we have a responsibility to ensure their survival.

Notes

3. J.M. Thiollay, "Area Requirements for the Conservation of Rain Forest Raptors and Game Birds in French Guiana." Conservation Biology, 1989, Vol. 3(2): 128-37.

4. William Newmark, "A Land-bridge Island Perspective on Mammalian Extinctions in western North American Parks." Nature, 1987, Vol 229: 430-32.

5. Christine Schonewald-Cox, "Conclusions: Guidelines to Management: A Beginning Attempt," in Genetics and Conservation: a Reference for Managing Wild Animal and Plant Populations, edited by Christine Schonewald-Cox, Steven Chamber, Bruce MacBryde and Larry Thomas, (London: The Benjamin/Cummings Publishing Company, Inc., 1983), pp. 415-16, 443-44.

6. Larry Harris, The Fragmented Forest: Island Biogeography Theory and the Preservation of Biotic Diversity, (Chicago: The University of Chicago Press, 1984), pp. 72-84.

7. Scott Robinson, Frank Thompson, Therese Donovan, Donald Whitehead and John Faaborg, "Regional Forest Fragmentation and the Nesting Success of Migratory Birds." Science, 1995 Vol. 267 (526): 1,987.

8. Elliot Norse, Ancient Forests of the Pacific Northwest, (Washington D.C.: Island Press, 1990), pp. 73, 84.

9. Walter V. Reid and Kenton Miller, Keeping Options Alive: The Scientific Basis for Conserving Biodiversity

, (Washington, D.C.: World Resources Institute, 1989), p. 15.

10. Calculated by multiplying regional frontier forest area by per hectare carbon estimates for forest areas, presented in R.K. Dixon, S. Brown, R.A. Houghton, A.M. Solomon, M.C. Trexler and J. Wisniewski, "Carbon Pools and Flux of Global Forest Ecosystems." Science, Vol. 263: 185-90. Dixon et al's estimates are for closed and open forests for both soil and above-ground vegetation. For this reason, and because these averages include degraded forest (which contains less carbon than intact forest) the figure presented in the text on total carbon stored in frontier forest is likely an underestimate. Soil carbon figures include peat. We used averaged per hectare carbon figures in estimating carbon stored in frontier forests that contain more than one dominant forest type (e.g. temperate and boreal forest).

11. John Perlin, A Forest Journey: The Role of Wood in the Development of Civilization, (New York: W.W. Norton and Company, 1989), pp. 18-19, 42-43.

12. World Resources Institute, World Resources 1992-93, (New York: Oxford University Press, 1992), p. 290.

13. George Ledec and Robert Goodland, Wildlands: Their Protection and Management in Economic Development, (Washington, D.C.: The World Bank, 1988), pp. 26-7.

14. Nels Johnson and Bruce Cabarle, Surviving the Cut: Natural Forest Management in the Humid Tropics

, (Washington, D.C.: World Resources Institute, 1993) p. 7.

15. Commission on Development and Environment for Amazonia, Amazonia Without Myths, Amazon Cooperation Treaty, 1992. p. xiv.