(Agencies)
Updated: 2007-12-30 11:37

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"They could be wiped out of California depending on how quickly the change happens," said Cameron Barrows, who studies the effects of climate change for the Center for Conservation Biology in Riverside.

Farther north, where wet, cold winters are crucial for the water supply of the entire state, warmer temperatures will lead to more rain than snow in the Sierra Nevada and faster melting in the spring.

Because 35 percent of the state's water supply is stored annually in the Sierra snowpack, changes to that hydrologic system will lead to far-reaching consequences for California and its ever-growing population.

Some transformations already are apparent, from the Sierra high country to the great valleys that have made California the nation's top agricultural state.

The snow line is receding, as it is in many other alpine regions around the world. Throughout the 400-mile-long Sierra, trees are under stress, leading scientists to speculate that the mix of flora could change significantly as the climate warms. The death rate of fir and pine trees has accelerated over the past two decades.

In the central and southern Sierra, the giant sequoias that are among the biggest living things on Earth might be imperiled.

"I suspect as things get warmer, we'll start seeing sequoias just die on their feet where their foliage turns brown," said Nate Stephenson, a US Geological Survey ecologist who is studying the effects of climate change in the Sierra Nevada. "Even if they don't die of drought stress, just think of the wildfires. If you dry out that vegetation, they're going to be so much more flammable."

Changes in the mountain snowpack could lead to expensive water disputes between cities and farmers. Without consistent water from rivers draining the melting snow, farmers in the Central and Salinas valleys could lose as much as a quarter of their water supply.

Any drastic changes to the state's $30 billion agriculture industry would have national implications, since California's fertile valleys provide half the country's fresh fruits, nuts and vegetables, according to the Union of Concerned Scientists' study.

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