May 3rd, 2012 by James Ayre
“Some people have assumed that biodiversity effects are relatively minor compared to other environmental stressors,” said biologist David Hooper of Western Washington University, the lead author of the Nature paper. “Our new results show that future loss of species has the potential to reduce plant production just as much as global warming and pollution.”
This is the first study to directly compare the loss of biodiversity to other environmental stresses.
The results strongly suggest the need for better efforts to protect biodiversity and the benefits that it brings.
“Loss of biological diversity due to species extinctions is going to have major impacts on our planet, and we better prepare ourselves to deal with them,” said University of Michigan ecologist Bradley Cardinale, one of the authors.
“These extinctions may well rank as one of the top five drivers of global change,” said Cardinale, an assistant professor at the U-M School of Natural Resources and Environment and an assistant professor in the Department of Ecology and Evolutionary Biology.
Studies done in the past couple of decades have shown that more biologically diverse ecosystems are more productive. They suggest that, as the currently very high levels of extinction continue, they will reduce the ability of ecosystems to provide clean water, food, and a stable climate.
The study was done by combining data from 192 previously conducted studies on the effect species richness has on ecosystem processes. The data was used to compare the effects of different environmental stresses on plant growth, and decomposition by bacteria and fungus.
The study found that in ecosystems where 21 to 40 percent of the species go extinct, plant growth is expected to be decreased by 5-10 percent, an effect that the researchers say is comparable to mild climatic warming, or increased UV radiation from stratospheric ozone loss.
With higher levels of extinction, the impact is much greater, and is similar to acid deposition on forests, ozone pollution, and nutrient pollution.
“Within the range of expected species losses, we saw average declines in plant growth that were as large as changes seen in experiments simulating several other major environmental changes caused by humans,” Hooper said. “I think several of us working on this study were surprised by the comparative strength of those effects.”
“The biggest challenge looking forward is to predict the combined impacts of these environmental challenges to natural ecosystems and to society,” said J. Emmett Duffy of the Virginia Institute of Marine Science, a co-author of the paper.
“This analysis establishes that reduced biodiversity affects ecosystems at levels comparable to those of global warming or air pollution,” said Henry Gholz, program director in the National Science Foundation’s Division of Environmental Biology, which funded the research.
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