High Mortality Reported for Eastern Trees

Trees in the biggest forest in the eastern United States appear to be dying at three times the natural rate, probably because of pollution, studies show.

The largest and most majestic trees in the forest, some of them more than 300 years old, are being hit the hardest, said Orie L. Loucks, an ecosystem scientist at Miami University in Oxford, Ohio.

“It’s a huge problem,” he said Thursday. “We are losing unique and irreplaceable older forests.”

Loucks is studying what is called the mixed mesophytic forest, which stretches from Ohio through West Virginia and Kentucky and into Tennessee.

He presented the findings at the annual meeting of the Ecological Society of America and the American Institute of Biological Sciences.

Historically, about 5% to 7% of the forest died each decade, as older trees gave way to younger growth. Loucks determined that the death rate is now as high as 15% to 20% per decade.

He said the biggest cause is probably ozone, produced by a reaction between auto exhausts and industrial pollutants. He said acid rain and nitrogen in rainfall, another consequence of pollution, are also hurting the trees.

Daniel Twardus, a forest health specialist with the U.S. Forest Service in Morgantown, W.Va., said he has seen accelerated tree mortality rates.

But he questioned whether enough data exists to blame air pollution.