Study says warming behind plants' move
LOS ANGELES - Striking new research in the Southern California mountains suggests recent warming is behind a massive die-off and rapid migration to higher ground by nine different plants, from desert shrubs to white firs.
Within 30 years, most had moved to elevations 200 feet above their previous growth range. The findings provide a glimpse of what could happen to the world's vegetation as the Earth faces global warming.
Scientists have long warned that human-caused climate change threatens to turn plants into refugees as they migrate to higher, cooler spots to survive. The latest study is the first to physically measure changes in plants' locations in connection with regional warming, whether man-made or part of a normal cycle, over the past three decades.
"The speed [of the plant movement] is alarming," said ecologist Travis Huxman of the University of Arizona in Tucson, who did not participate in the study. "It means that we'll likely see vegetation shift a lot faster than we might think."
However, at least one specialist suggested that prolonged drought, not climate change, could be the cause of the die-off and migration.
Researchers from University of California, Irvine, in 2006 studied the 10 most common plant species in the Santa Rosa Mountains east of Los Angeles at different elevations. With a measuring tape, they recorded the type of plant every 400 feet from sea level to over 8,000 feet, and compared the distribution to a survey that was done in the same area in 1977.
The Santa Rosa Mountains host diverse habitats, including conifer forest, chaparral, woodland, and desert scrub. Since the 1970s, the region has seen average temperatures rise 2 degrees as well as extended periods of drought. To scientists' surprise, they found scores of dead trees and shrubs at lower altitudes, but flourishing plants uphill. The habitats of nine of the 10 plant species studied crept an average 213 feet up the mountain face, the study found.
"The plant death was striking, and occurred in most species," said study coauthor Michael Goulden of UC Irvine. "The occurrence of plant death was obvious to everyone living in that area."
The results appear in yesterday's issue of the journal Proceedings of the National Academy of Sciences.
