Western US - Dying forests and lack of water for crops

Study: Western forests dying at increasing rate

(AP) Trees in old growth forests across the West are dying at a small, but increasing rate that scientists conclude is probably caused by longer and hotter summers from a changing climate.

While not noticeable to someone walking through the forests, the death rate is doubling every 17 to 29 years, according to a 52-year study published in the Friday edition of the journal Science. The trend was apparent in trees of all ages, species, and locations.

"If current trends continue, forests will become sparser over time," said lead author Phillip J. van Mantgem of the U.S. Geological Survey's Western Ecological Research Center.

"Eventually this will lead to decreasing tree size," he said. "This is important because it indicates future forests might store less carbon than present."

Old growth forests, particularly those in the Northwest, store large amounts of carbon, making them a resource in combatting global warming, said Jerry Franklin, a professor of forest ecology at the University of Washington. But as trees die, they decompose and give off carbon dioxide, contributing to the amount of greenhouse gases. Young forests store very little carbon, and it takes hundreds of years to replace old growth, he said.

The researchers considered several other possible causes for the higher death rate — air pollution, overcrowding of young trees, the effects of logging, large trees falling on small ones, and a lack of forest fires, which keep forests healthy. But the data showed the trend affected trees young and old, in polluted and clean air, in crowded and sparse stands and at different elevations.

The likely cause, they concluded, was warmer average temperature across the West, about 1 degree over the study period, said co-author Nathan L. Stephenson, also of the USGS Western Ecological Research Center. That results in greater stress on the trees from lack of water, leaving them vulnerable to disease and insects.

Stephenson said the rising death rate could also produce a cascading decline in forests that leads to less habitat for fish and wildlife, an increased risk of wildfires, and a vulnerability to sudden forest die-offs.
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Meanwhile: Calif. farmers slash planting to cope with drought

(AP) Some of the nation's largest farms plan to cut back on planting this spring over concerns that federal water supplies will dry up as officials deal with the drought plaguing California.

Farmers in the Central Valley said Thursday they would forego planting thousands of acres of water-thirsty canning tomatoes and already have started slashing acreage for lettuce and melons.

As growers in Fresno and Kings counties prepared to sow their dry fields with tomato seeds this week, the giant water district that supplies the irrigation for their sprinklers warned them to think again.

Computer models of the state's parched reservoirs and this year's patchy snowfall showed shortages so extreme that federal officials could slash supplies down to zero, managers at the Westlands Water District told their members in an emergency conference call.

"We thought it was important to talk to our growers so they can make important planting decisions," said Sarah Woolf, a spokeswoman for Westlands, the coalition of giant agribusinesses in the state's fertile interior.

Officials with the U.S. Bureau of Reclamation and the state Department of Water Resources plan to announce next month how much water they'll speed to farms and cities.

But farmers say that's too late, since they need to decide what to plant now, as they negotiate with banks for crop loans. Growers who are struggling to revive shriveled vines and dying trees say they're panicked at the thought of having to solely rely on well water of dubious quality.

"It's ugly," said Shawn Coburn, who grows 1,000 acres of almonds in Fresno County. "I've heard from probably eight to 10 guys whose lines of credit are frozen until they can show they have water."