Climate change could affect California plant life

ShareThis

If temperatures rise rapidly in California this century, up to two-thirds of the state's native plants might lose large swaths of suitable habitat, according to a new study. Scientists from the University of California Berkeley, Duke University and other institutions released maps this week showing how 2,300 plants found only in the state might respond to the effects of global warming."The pace of climate change in the next 100 years poses a very serious threat to California's native plants," said David Ackerly, a UC Berkeley biology professor and an author of the new study, published in the PLoS One, the Public Library of Science. Plants can respond to changing climate conditions over thousands of years, Ackerly said. "But in less than a century, there is very little chance for plants to establish new populations and to migrate to keep up with these dramatic changes," he said.Over the past few decades, climate scientists have found that plants respond to rising temperatures by climbing to higher elevations seeking a cooler climate. The movement can be north or south, depending on the mountain ranges.Yet plants die when they reach mountaintops and can't move any higher, scientists have found. Movement is also hampered by loss of habitat and competition from invasive species.According to NASA, surface temperatures rose almost 1 1/2 degrees in the past century, but much of that was in the past 50 years. Eleven of the past 12 years (1995-2006) are the warmest since accurate record keeping began in 1850.California is known for its Mediterranean climate of hot, dry summers and cool, wet winters. Most susceptible to species loss would be the foothills of the northern Sierra Nevada, the study found.In contrast, researchers found that the central coast from the Big Sur region to Mendocino County would remain rich in plant life even if most plants couldn't migrate. If plants could migrate and establish new populations, they might spread north to southern Oregon, where diversity could expand.The authors of the study say they cannot predict the fate of any specific species. However, their work included focusing heavily on nearly 600 of the most-studied native plants, including the live oak, blue oak, scrub oak, California bay laurel, whiteleaf manzanita and the San Francisco wallflower.Scientists said they could not collect enough data to accurately predict what may happen to California's most iconic tree -- the redwood. They lacked the fog forecasts under global warming models that would help project the movement of the coastal trees. But the authors noted that the big established redwoods and oaks might be saved."They may become the living dead," Ackerly said. "The old ones will remain but the seedlings won't grow. All it does is forestall the inevitable."The analysis was based on two climate models. Plant location information was obtained from databases including the California Academy of Sciences and the Jepson Herbarium at UC Berkeley.If emissions continue at their current rate and carbon dioxide concentrations hit 970 parts per million in the atmosphere in the period from 2080-2099, then up to 66 percent of plants would disappear from 80 percent or more of their present ranges, the study predicts.But if the emissions drop to below 1990 levels by the end of the century, carbon dioxide concentrations would reach 550 parts per million, researchers predict. At that level, the impact would be much less on native plants, the authors of the study said. Currently, levels are 387 parts per million, up almost 40 percent since the Industrial Revolution and the highest for at least the past 800,000 years.Plants would have to move up to 95 miles to keep up with changing climate over the next century. The plants could move in different directions, potentially breaking up familiar California native plant associations, the authors said. (E-mail Jane Kay at jkay(at)sfchronicle.com)(Distributed by Scripps Howard News Service, www.scrippsnews.com.)