June 25, 2008 -- The ranges of up to two-thirds of the 2,387 plant species found only in California may shrink by more than 80 percent under predicted climate change.
An 80 percent reduction in habitat in 100 years is the threshold for classification as "critically endangered" by the International Union for the Conservation of Nature, which maintains the well-known Red List of Threatened Species.
"This is the first time that anyone has made the attempt to look at so many species, and I think it's kind of a wake-up call that we can expect some pretty dramatic changes," said plant ecologist Philip Rundel of the University of California, Los Angeles, who was not a part of the study.
"It's very clear that we're going to lose a lot of species to global warming, and when you get to species that are narrowly restricted like so many in California, the problem is worse," added Peter Raven, President of the Missouri Botanical Garden in St. Louis.
To make the predictions, a team led by David Ackerly at the University of California, Berkeley, combined regional models for predicting climate change with known information about the current range of California plants to predict what regions would have a matching climate in the future.
In general, plants will retreat northward or to higher elevations as climate warms, the researchers reported online in the journal PLoS ONE.
"We found several places we're calling 'climate change refugia,'" said the study's first author, Scott Loarie of Duke University in Durham, N.C.
"These are places where a large diversity of these species might persist. What's important about these refugia is that they include the plants that are really going to be threatened," he added. "It's important that these areas are set aside, but also whether these plants can get to them."
Indeed, how quickly and successfully plants can move across the landscape is one of the big uncertainties in the projections, Loarie said.
"The changes expected to occur are 10 times faster than the last ice age," he said. "This is happening faster, and it's happening against a much more fragmented landscape. As these patches of native vegetation become increasingly smaller, it's hard to imagine, say, a native wildflower going from the Sierra Nevada foothills and crossing Sacramento to the coastal mountains."
Maintaining corridors for plants to move through should be a priority, both Raven and Rundel told Discovery News.
"We tend to think about corridors for wildlife, but in the longer run we need to think about genetic corridors," Rundel said. The genetic variation present in a particular plant species at the southern end of its range may be important for its survival in more northerly environments as the climate warms, for instance.
Another uncertainty in the current projections is how much temperatures will rise, Loarie said. However, current emissions are on pace to exceed the more extreme climate scenario the group considered, the previous worst-case scenario considered by the Intergovernmental Panel on Climate Change.
Refining these models to include other local conditions like soil type should be the next step, Rundel said.
"If you talk to anyone that's a park superintendent today, one of the questions they're being asked is, 'What are you going to do about climate change? Are our parks going to be in the right place?'" he said.
Botanical gardens and seed banks may become important resources for assisting with the plants' migration, Raven said. Those kinds of organizations "are always interested in restoration. The difference is, you might be restoring them in different places."
Related Links:
Discovery News blog: Environmental CaseMaps Showing Plant Ranges in California
How Stuff Works: Climate Change Discovery Earth Liveour sites
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