Will climate change exceed life's ability to respond? Biodiversity in a Warmer World, published in the Oct. 10, 2008 issue of the journal, Science, illustrates that cross-disciplinary research fostered by the Smithsonian Tropical Research Institute in Panama clearly informs this urgent debate.
As an extremely diverse region of rainforest and coral reefs, the tropics may have the most to lose as a result of global warming. Some disagree, arguing that tropical organisms will be favored as their ranges expand into temperate areas. Few empirical studies provide specific answers to help us choose conservation and mitigation measures.
Science asked Jens Svenning, University of Aarhus, Denmark and Richard Condit of the Smithsonian's Global Earth Observatory Network to review two papers about species range change:
In a range analysis for plants and insects on a mountain slope in Costa Rica, Colwell et al. show that a 3.2˚ C increase in temperature threatens 53 percent of the area's species with lowland extinction and 51 percent with range shift gaps, meaning that they have nowhere else to go.
The other study they reviewed, by Moritz et al., follows historical range expansions and contractions for small mammals in Yosemite National Park in California, USA and shows that ranges may contract dangerously as they are pushed further and further up mountain slopes.
To provide the proper perspective for this work Svenning, who held a postdoctoral fellowship with the Smithsonian's GEO network in 2000-2002 and Condit cite empirical work by colleagues at the Smithsonian and others:
In a 2001 Science article by STRI staff scientist Carlos Jaramillo et al., plant pollen diversity in rock cores from northern South America revealed that warming events in the tropics over 60 million years were not particularly detrimental, with the caveat that warming in fragmented landscapes or crossing a temperature threshold could cause severe extinctions in the future.
Extant species that evolved in warmer climates should retain the ability to tolerate warmer climates in the future, as argued in a 2001 issue of Science by Eldredge Bermingham, director of STRI and Christopher Dick, professor of ecology and evolutionary biology at the University of Michigan at Ann Arbor.
It is not clear which factors (temperature, moisture, competition with other species, habitat limitation) are the primary causes of tropical extinctions. Drought tolerance, however, definitely limits tropical plant distributions. This was reported in the May 2007 issue of Nature by Bettina Engelbrecht, research associate and lecturer at San Francisco State University, and colleagues.
Condit and Svenning also cite their own studies from the tropics and temperate areas where other drivers of extinction are at work. They call for more discoveries of the sort that often result when researchers are brought together in places like STRI's facilities in Panama, where camaraderie fuels critical ecological research within an intellectual context that encourages a deep time and wide world perspective.
- Jens-Christian Svenning and Richard Condit. Biodiversity in a Warmer World. Science, 2008; 322: 206-207
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