Old growth western US forests struggling for survival

Trees in old growth forests across the Western US are dying at a small, but increasing rate. Global warming which decreases the moisture in the trees as the temperature rise invites bark beetles to take up residence in them.captphoto_1232692085846-1-0

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 Journal Science.  Apparently trees of all ages, species, and locations are falling. “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 combating 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.

Other possible causes for the higher die off include air pollution, overcrowding of young trees, the effects of logging, large trees falling on small ones, and a lack of forest fires. The data shows this trend affected trees young and old, in polluted and clean air, in crowded and sparse stands and at different elevations.
Warmer than average temperatures across the West, about 1 degree over the study period, said co-author Nathan L. Stephenson of the USGS Western Ecological Research Center cause greater stress on the trees from lack of water, leaving them vulnerable to disease and insects. This decline could lead to less habitat for fish and wildlife, an increased risk of wildfires, and a vulnerability to sudden forest die-offs. The death rate increase varied, with the highest in California’s Sierras, from about 0.9 percent in 1980 and rising to about 1.3 percent.

Not everyone agrees with the above consensus however, Barbara Bond, a professor of forest physiology at Oregon State who was not involved in the study, much additional work would have be done before any rational scientist would draw some cause and effect,” she said.

The geological survey paid for the study, which examined data between 1955 and 2007 in 76 research plots in British Columbia, Washington, Oregon, California, Idaho, Colorado and Arizona. The average age of the forests examined was about 450 years, with some as old as 1,000 years. Of the 59,736 trees counted, 11,095 died over the study period.

Now is the time to do all we can one person at a time to help the trees by cutting our carbon foot print and decreasing pollution and use less  microwave energy. – Mother Nature

Study: Western forests dying at increasing rate – JEFF BARNARD, AP

Friday January 23, 2009 as reported in Yahoo News. dyingforests


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