Global warming threatens forests, study says

By Azadeh Ansari | CNN

Forests in the Pacific Northwest are dying twice as fast as they were 17 years ago, and scientists blame warming temperatures for the trend, according to a new study.  The study, to be released Friday in the journal Science, is the first large-scale analysis of environmental changes as contributing factors in the mortality of coniferous forests.

The data for this research was gathered by generations of scientists over a 50-year period at multiple sites in Oregon, Washington, California, Arizona, Colorado, New Mexico and southwestern British Columbia. Seventy-six forest plots, all more than 200 years old, were monitored by scientists doing some of the most rudimentary research — counting trees.

“It’s not a happy story, but, an important one,” said Phillip van Mantgem, a research ecologist with the U.S. Geological Survey and the lead author of the study. “These are beautiful places. They do change and respond to their environment, sometimes quickly.”

“If in your hometown where you live, the death rates of your friends and neighbors doubled and there are no compensating birth rates, wouldn’t you want to figure out what’s going on?” said Nathan Stephenson, research ecologist with the U.S. Geological Survey and one of the authors of the report.

The study primarily focused on three types of coniferous trees: pines, firs and hemlocks. Older-growth forests — some up to 500 years old — have trees of all ages, and researchers found that mortality rates have increased for all age groups. Since mortality rates went up across the board, scientists ruled out a number of other possible causes, including ozone-related air pollution, long-term effects of fire suppression and normal forest dynamics.

Read on here.


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