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Scientists develop global biodiversity scenarios for the year 2100

Land-use changes are likely to be the biggest factor affecting biological diversity over the next hundred years, according to an international group of scientists who have developed global scenarios for biodiversity in the year 2100.



Laura Huenneke, head of the biology department at New Mexico State University. (NMSU photo)

New Mexico State University biologist Laura Huenneke, a member of the international team, said the group's work represents a new approach to the study of changes in biological diversity -- that is, the variety of plants and animals that live in particular areas.

Scientists from around the world contributed their expert knowledge on different ecosystems as the team identified the most important causes of changes in biodiversity and developed models to project the possible impacts. The scientists' models project that the greatest proportional changes in biodiversity in the 21st century are likely to occur in sensitive Mediterranean-climate and grassland ecosystems.

By comparison, desert ecosystems like that in New Mexico are expected to experience relatively moderate changes in biodiversity, Huenneke said. That is largely because "desert diversity is not as high to start with as tropical diversity, and availability of water would tend to limit human development in arid regions over the next 50 to 100 years," she said.

The scientists reported on their global biodiversity scenarios in the March 10 issue of Science, the weekly journal of the American Association for the Advancement of Science.

"Global biodiversity is changing at an unprecedented rate as a complex response to several human-induced changes in the global environment," the scientists state in the article. "The magnitude of this change is so large and so strongly linked to ecosystem processes and society's use of natural resources that biodiversity change is now considered an important global change in its own right."

Osvaldo Sala of the University of Buenos Aires, Argentina, is the lead author of the report, co-authored by Huenneke and 17 other scientists from universities around the world.

The project is unusual because it brought together scientists who have specialized "in all the biomes (life zones) of the world, from the arctic tundra to the hot desert and from tropical rainforests to freshwater ecosystems," said Huenneke, whose research has focused on desert ecosystems.

"It's a relatively new approach," she said. "Astronomers and physicists do this (global collaboration) all the time, but ecology hasn't been done that way in the past. Usually, ecological studies are done by small groups of researchers studying a particular location or ecosystem. We need a wider understanding and better predictive ability."

The researchers' biodiversity scenarios are based on current trends in factors that are known to affect biodiversity -- changes in atmospheric carbon dioxide and nitrogen deposition, climate changes, biotic exchanges (establishment of exotic species of plants or animals) and land-use changes -- and the known sensitivity of different ecosystems to these changes.

"Our rankings of the relative impact of these different drivers of change came from the experience of the researchers who have expert knowledge on each of the biomes," Huenneke said. "What's interesting is how strong the patterns are. Nearly every biome is most strongly affected by land-use changes."

Factors used in predicting land-use changes included trends in human population growth and consumption patterns, she said. As more land is converted to agricultural uses, for instance, less habitat is available to sustain a variety of plant and animal species.

The models project that the most dramatic changes in biodiversity will occur in Mediterranean-climate systems and grassland ecosystems, which are most susceptible to land-use changes and the other drivers of change. Northern temperate ecosystems are expected to experience the least biodiversity change because major land-use changes have already occurred in those areas. Similarly, change is projected to be not as great in other areas where land-use changes are expected to be somewhat limited by climate or availability of water -- deserts and arctic regions, for instance.

The biggest uncertainties in the projections have to do with the possible interactions among the various causes of biodiversity change, Huenneke said.

"One of the critical points that came out of this project is that there's a huge difference in assuming these changes occur independently and assuming there are interactions between the changes," she said. "It reinforces the importance of studying these interactions."

Photo is available at http://kiernan.nmsu.edu/newsphoto.
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PHOTO: Huenneke.jpg
CUTLINE: Laura Huenneke, head of the biology department at New Mexico State University. (NMSU photo)

Karl Hill
March 13, 2000