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Study: Extinction Could Rival Climate Change

By Joshua E. Brown, Joshua.E.Brown@uvm.edu,
802/656-3039

Study: Extinction Could Rival Climate Change


RACC Team member - Carol Adair

Over the last two decades, there has been growing concern that very
high rates of modern extinction -- loss of plant and animal species due
to habitat destruction, overharvesting and other human-caused
environmental changes -- could reduce nature's ability to provide goods
and services that people need, "like food, fuel, carbon storage, clean
water, and habitat," says the University of Vermont's Carol Adair.

But it's been unclear how these species losses stack up against other
human-caused environmental changes that affect ecosystem productivity.

Now, a new study in the journal Nature provides a sobering answer:
extinction of plant and animal species appears to damage ecosystem
health as much as climate change, pollution and other major forms of
environmental stress.

The study -- led by an international research team, including UVM's
Adair -- was published May 2.

Species matter

The study is the first comprehensive effort to directly compare the
impacts of biological diversity loss to the anticipated effects of a
host of other human-caused environmental changes.

The results highlight the need for stronger local, national and
international efforts to protect biodiversity and the benefits it
provides, according to the researchers, who are based at nine
institutions in the United States, Canada and Sweden.

"The take-home message is that loss of species is as important as
climate change and pollution," says UVM's Adair, an expert on global
change in the Rubenstein School of Environment and Natural Resources.
"When we're working on solving these other problems we should make sure
the solutions don't negatively impact biodiversity."

"These extinctions may well rank as one of the top five drivers of
global change," said Brad Cardinale, a University of Michgan ecologist
and co-author on the study.

"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 new
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."

Global synthesis

In their study, Hooper and colleagues used combined data from a large
number of published studies to compare how various global environmental
stressors affect two processes important in all ecosystems: plant
growth and the decomposition of dead plants by bacteria and fungi. The
new study, funded by the National Science Foundation and the National
Center for Ecological Analysis and Synthesis, involved the construction
of a database drawn from 192 peer-reviewed publications about
experiments that manipulated species richness and examined the impact
on ecosystem processes.

This global synthesis found that in areas where local species loss this
century falls within the lower range of projections (loss of 1 to 20
percent of plant species), very few impacts on plant growth will
result, and changes in species richness will rank low relative to the
impacts projected for other environmental changes.

In ecosystems where species losses fall within intermediate projections
(21 to 40 percent of species), however, species loss is expected to
reduce plant growth by 5 to 10 percent, an effect that is comparable to
the expected impacts of climate warming and increased ultraviolet
radiation due to stratospheric ozone loss.

At higher levels of extinction (41 to 60 percent of species), the
impacts of species loss ranked with those of many other major drivers
of environmental change, such as ozone pollution, acid deposition on
forests 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 was surprised, and most of the people in the study were surprised,
to see species loss rank up there with all these other changes," UVM's
Adair said.

Policy points

The strength of the observed biodiversity effects suggests that
policymakers searching for solutions to other pressing environmental
problems should be aware of potential adverse effects on biodiversity,
as well, the researchers said.

"For example, one of the things we can do about climate change is to
use biofuels," say Adair, "but some biofuels incentives result in
rainforest destruction -- palm oil plantations and soybeans instead of
rainforests -- so you're losing diversity." Instead, Adair points
towards several international projects that seek to decrease greenhouse
gas loads and also preserve biodiversity.

Still to be determined is how diversity loss and other large-scale
environmental changes will interact to alter ecosystems. "The biggest
challenge looking forward," said J. Emmett Duffy of the Virginia
Institute of Marine Science, a co-author of the paper, "is to predict
the combined impacts of these environmental challenges to natural
ecosystems and to society."

This story is adapted from materials prepared by Jim
Erickson at the University of Michigan.

Related Link: Nature Study -
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11118.html

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