Ask biologists about biodiversity and they're likely to agree that the subject commands an increasing amount of their attention. But they may be at a loss to cite the key research in the field. Although biodiversity--the study of the planet's varied species, genes, and habitats, and the effort to preserve them--is building as a scientific endeavor and an environmental buzz-word, there is no consensus on what this science will or should be like.
E.O. Wilson and F.M. Peter, eds., Biodiversity.
J.A. McNeely, et al., Conserving the World's Biological Diversity.
W.V. Reid, and K.R. Miller, Keeping Options Alive: The Scientific Basis for Conserving Biodiversity.
N. Myers, A Wealth of Wild Species.
M.L. Oldfield, The Value of Conserving Genetic Resources.
So far, however, that flurry of activity has not translated into a recognized canon for this emerging scientific field. "There are not really any central articles," notes Dan McKenzie, fishery ecologist at the Environmental Protection Agency's Environmental Research Laboratory, located in Corvallis, Oreg.
The term "biodiversity" was coined in 1986 by a few leading biologists, including Raven and E.O. Wilson, Mellon Professor of the Sciences at Harvard University. The researchers came up with the word during a symposium at the Smithsonian Institution, the proceedings of which (Biodiversity, National Academy Press, 1988) are regarded by some as containing the field's most seminal literature to date. "We needed a word that would take what a lot of us were thinking about, that would serve as a little flag for Congress," says Dan Janzen, an entomologist from the University of Pennsylvania helping to set up biodiversity preserves in Costa Rica.
Consequently, the concept reflects a broad spectrum of ideas. Some will argue that biodiversity is nothing more a jazzed-up name for centuries-old studies like systematics or natural history, perhaps with a little ecology and biogeography thrown in. Some see conservation science and restoration biology as the core of biodiversity. Others contend that biodiversity encompasses these disciplines and more. "It's a trans-discipline," says Gary Hart-shorn, vice president for conservation science at the World Wildlife Fund (WWF) in Washington, D.C.
Despite such confusion, efforts are under way to develop a research as well as a policy agenda for biodiversity. "We certainly do consider it to be an emerging area," says Jim Edwards, deputy division director of biotic systems and resources at the National Science Foundation. Several papers are in press or are being prepared that could clarify and set future standards for how biodiversity should be assessed, conserved, and used in the development of products such as pesticides and food crops.
One key theme is the need to tie fundamental research to useful applications. "We have the potential to unlock immense new sources of wealth," says Wilson. "It may hold the key to substantial improvements in the standard of living, environment, and income in the Third World."
"One thing is quite clear," says EPA's McKenzie. "There are difficulties in defining what it is, how we measure it and define it." As Edwards says, "How do you determine what biodiversity is at a site, and how do you determine that significant changes have occurred at this site?"
One reason for the confusion is that biodiversity is an imprecise concept. "If followed to the extreme, biodiversity becomes synonymous with everything out there in the outside world," says Raven. It could refer, for example, to genetic diversity, or to the variety of species, or even habitats.
There is even diversity among the researchers attracted to this problem. "What you've got is a bunch of people like myself all moving this amorphous thing forward, each one bringing their own past history and their own agency," says Janzen.
A generation ago, researchers studied biodiversity by asking what determined the number of species in a particular community. Then came Smithsonian entomologist Terry Erwin. In 1982 Erwin counted 163 beetle species living in one kind of tropical tree. Extrapolating from that figure, he concluded that there are probably 30 million species of tropical arthropods in the world. The previous estimate had been only 1.5 million. That calculation "really changed our view of how many species there are on earth," says Frank Talbot, director of the National Museum of Natural History in Washington, D.C. ("Tropical forests: Their richness in Coleoptera and other arthropod species," The Coleopterists Bulletin, 36:74-5, 1982).
Now, Erwin says, new work in Peru is showing that his estimate, startling as it was, may have been far too low. And British biologist Robert May has since pointed out that any estimate is really just a wild guess and has outlined what research needs to be done to home in on a more exact number ("How many species are there on earth?" Science, 241:1441-19, 1988).
In the past, scientists would go into an area to survey just one type of organism. Now, to get a handle on how the ecosystem works, researchers have begun inventories of many kinds of plants and animals. Because they are identifying abundance and distribution patterns, much of the work in biogeography and ecology also falls under the biodiversity rubric. "The unique twist [now] is the coupling of the understanding of the variety of life and what that means in terms of the stability of systems," says Sy Sohmer, biodiversity adviser at the United States Agency for International Development in Washington, D.C.
Despite the emphasis on numbers of species, researchers have realized that areas where rapid speciation is occurring may be even more important than areas where there are lots of species, even rare ones, but no new ones evolving. That point is made by Erwin in a policy forum piece due to appear this spring in Science. From Erwin's perspective, understanding the lineages of species may be a better goal of biodiversity than identification and enumeration of the species themselves. Toward this end, scientists are harnessing molecular and numerical analyses to better determine relationships between species. Scientists are addressing these issues on several fronts. Researchers are pushing for biodiversity to be a key item on the agenda of the Conference on Ecology and Development, to be held in Brazil in June 1992. And there's an international workshop being planned for this coming October, at which biologists plan to hammer out a conceptual framework based on a paper written by Otto Solbrig, Bussey Professor of Biology at Harvard University and a past president of the International Union of Biological Sciences.
Solbrig's 60-page document outlines a unified theory that ties together diversity on the scale of ecosystems, organisms, and genetics. "It has big input from genetics, ecology, and evolutionary biology, but none at all from conservation biology," notes Solbrig. "We're trying to create the scientific basis from which they [conservationists] will work."
Part of that basis will be documenting the effects of species loss. "I feel the issue of loss of diversity is real, but one has to, as a scientist, find out what the significance is," he explains. "There is an awareness that there has to be more [scientific] rigor, so we will know what to do."
However, many experts don't think the decisions can wait. "We don't even know within an order of magnitude what the number of species are," says Thomas Lovejoy, assistant secretary for external affairs at the Smithsonian. Yet those plants and animals are disappearing at an alarming rate, too fast for efforts to save individual species to keep ahead of extinction. Adds WWF's Hartshorn, "A lot of us fear that we truly have this decade to effect some very substantial changes."
One important step, say scientists, is to immediately set aside habitats to be protected. "There needs to be an organized worldwide effort to do it [inventories] in a systematic fashion, with checkpoints along the way," says Lovejoy.
Where inventories are taking place, scientists are also trying to implement standards. But the effort is having mixed success. The U.S. Fish and Wildlife Service and the Smithsonian are producing books on methods to study and inventory birds, plants, mammals, and amphibia, with the hope that these methods will be adopted worldwide. And in tropical forests, Hartshorn says, many people are advocating that surveys be done on 2.5-acre plots. But Stephen Hubbell, a Princeton University tropical forest biologist, is pushing for plots 50 times as large. He is attempting to set up a network of study plots worldwide.
Some argue that modeling is the most efficient way to figure out quickly what habitats are not being protected. In Idaho, U.S. Fish and Wildlife ecologist J. Michael Scott is using computer modeling to help conservationists decide where they need to focus their energies first.
Scott's program analyzes vertebrate distributions, wildlife habitat types, and vegetation maps generated from satellite photos. These maps, when overlaid with land ownership and use maps, make clear which habitats are most threatened.
"In terms of a biological inventory, by the time we finished it, we would have lost a lot of what we would hope to protect," says Scott. "The budgets [to do complete inventories] aren't there, and I don't think they are going to be there."
However, Scott's approach doesn't sit well with some scientists. "I see it as a quick and dirty way of trying to get at species diversity," says Raven. "I don't think much of that." No matter how they are done, inventories are really just the first step for conservation biologists. To Janzen, these efforts pave the way for the real mission of biodiversity: a search for useful medicines, pesticides, food crops, and other products among these untapped resources.
Concomitant with that purpose is the need for investigators to come up with ways to place an economic value on biodiversity so it can be more readily factored into economic equations for policy planning. "What we have not done very well is translate scientific justification [for protecting biodiversity] into lay-man's terms and economic justification," says Hartshorn. One such effort was attempted by Charles Peters of the New York Botanical Garden and two colleagues in a 1989 commentary in Nature ("Valuation of an Amazonian rainforest," Nature, 339:655-6, 1989).
Thus, people like Hartshorn and Janzen see the scientific challenge as being much different from what Solbrig or Erwin would concentrate on. Says Janzen: "There is a learning that needs to go on about how to read what nature is doing."