California trees, shrubs flee uphill as climate disrupted


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Whither California’s golden cup oak trees, its lilacs and its agave plants? They are creeping up mountainsides, no longer able to survive at their normal elevations. That’s the conclusion of two University of California, Irvine researchers who compared a 1977 study of the vegetation on the north face of Santa Rosa Mountains, near Idyllwild, with the conditions today.

The mean elevation of nine of the 10 most abundant species studied rose, with an average gain of 213 feet.


The culprit is clearly climate change, the researchers said, a phenomenon that scientists concur is caused by emissions of carbon dioxide and other greenhouse gases from coal and gas-fired power plants, automobiles and other industrial sources. Warmer temperatures and longer dry spells have killed thousands of trees and shrubs over the past 30 years, the researchers said in the study that will be published online this week in the Proceedings of the National Academy of Sciences.

‘Plants are dying out at the bottom of their ranges, and at the tops of their ranges they seem to be growing in and doing much better,’ said Anne Kelly, a graduate student at UCI who conducted the survey with Earth System Science professor Michael Goulden.

In the past 30 years, temperatures rose an average of 2 degrees Fahrenheit in the area, and extended droughts occurred in 1987-1990 and 1999-2002. In the UCI study, 141 species were identified, with a focus on the 10 most abundant at different elevations: white fir, Jeffrey pine trees, golden cup oak trees, sugar bush, California lilac, Muller scrub oak, creosote bush, ragweed, brittle bush shrubs and agave plants.

The findings in the Santa Rosa mountains echo a survey published in June in the the online journal PLoS One, which predicted that two-thirds of California’s unique plants, some 2,300 species that grow nowhere else in the world, could be wiped out across much of their geographic range by the end of the century, due to climate change.

-- Margot Roosevelt