 Rising temperatures have forced many plants to creep to higher elevations to survive, researchers reported on Thursday. More than two-thirds of the plants studied along six West European mountain ranges climbed an average of 29 meters in altitude in each decade since 1905 to better conditions on higher ground, the researchers reported in the journal Science. "This is the first time it is shown that climate change has applied a significant effect on a large set of forest plant species," said Jonathan Lenoir, a forest ecologist at AgroParisTech in France, who led the study. "It helps us understand how ecosystems respond to temperature changes." Earlier this week, U.S. researchers warned warming temperatures could turn many of California's native plants into "plant refugees" looking for more suitable habitats. They concluded that a warming climate and rainfall changes would force many of the U.S. state's native plants to range north or to higher elevations or possibly even go extinct in the next 100 years. The French team's findings suggest plants at high altitudes face the same or greater impacts from rising temperatures, Lenoir said in a telephone interview. "Plant species move where it is optimal for them to grow," Lenoir said. "If you change these optimal conditions, species will move to recover the same conditions." Using database on plant species found at specific locations and elevations stretching back to 1905, the researchers showed many plants have steadily crept higher to conditions best suited for survival and growth. Plants move higher by dispersing their seeds in the wind, which blows them to higher elevations and cooler temperatures similar to their former location, Lenoir said. The researchers tracked 171 forest plant species during two periods -- between 1905 and 1985, and from 1986 to 2005 -- along the entire elevation range from sea level to 2,600 meters. They found that two-thirds of the plants responded to warming temperatures over that time by shifting to higher altitudes. Plants at higher altitudes also appear most sensitive to warmer conditions because slight temperature changes at higher altitudes have a bigger impact, he added.