7:10 AM Mar 13, 1996


Penang, Malaysia, Mar 12 (TWN/Peter Montague ) - Trees across the United States are sick or dying from pollution and destructive logging, prompting frantic scientists to study ways to stem the trend, but forest authorities seem to want to believe otherwise.

A new book that takes a close look at forests in the United States says the high rate of tree deaths is widespread but it describes as disappointing the attitude of the U.S. Forest Service toward the problem.

The book 'The Dying of the Trees' by Charles Little, blames tree deaths on either acid rain as is the case in New England, North Carolina and Indiana, or killer smog in the case of California. In Arizona and New Mexico and elsewhere, it's excessive ultraviolet light filtering through the earth's damaged ozone shield, it says.

In other places, it's pesticides, or toxic heavy metals released by burning coal and oil, or rising temperatures as a result of global warming in the case of Alaska.

In Colorado, Oregon and Washington state, trees are succumbing to destructive forestry practices that leave forests weak and unable to withstand extremes of weather or attacks by insects or fungi, the book says.

It says scientists are playing catch-up now, conducting studies that may explain the phenomenon.

The book cites a study by botanist Hubert Vogelmann of the University of Vermont on Camel's Hump, a 1,245-metre peak in the Green Mountains.

His study of the 'undisturbed' forest began in 1965 with no particular purpose in mind other than to gather knowledge about nature. Describing Camel's Hump as a healthy ecosystem, he studied the types of trees, measured their sizes and gathered data on the other aspects of the ecosystem.

Periodically, he re-surveyed Camel's Hump and a pattern began to emerge: the trees were dying. His survey in 1979, compared to the baseline study of 1965, showed a 48 per cent loss of red spruce; a 73 per cent loss of mountain maple; a 49 per cent loss of striped maple, and a 35 per cent loss of sugar maple.

Results of Vogelmann's study bore similarities to those made on the Black Forest of Germany and in southern Canada, which pointed to acid rain as the most likely cause of the tree deaths.

Acid rain occurs when coal and oil are burned, releasing sulphur which combines with rain (or fog or snow) to make acid precipitation.

After World War-II, the US saw a massive rise in use of fossil fuels, coal and oil. The resulting smoke was obviously harmful. In Donora, Pennsylvania in 1948, 20 people were killed and half the town's population fell ill because of coal smoke in the air. In London, in 1952, 4,000 people were killed by coal smoke during a pollution episode.

The official response in the 1950s was to build smokestacks hundreds of metres high to dilute the pollution. Today, the Ohio River valley is still dotted by enormous coal-burning power plants with stacks as high as 300 metres. The tall stacks allow the sulphurous pollution to travel 1,500 km or more, where it forms acid rain across the Adirondack Mountains of New York, and across northern New England and southern Canada.

What Vogelmann revealed by studying Camel's Hump for 30 years, the book says, is that acid rain does not affect just the trees, but the soil and thus the entire ecosystem.

Soil contains a large amount of aluminum silicates, which acid rain dissolves. These then find their way into the roots and into the vascular system, clogging the roots and preventing plants from taking in adequate nutrients and water. The trees are weakened as a result and may then fall prey to extreme cold, or to insects or pathogens.

Acid rain also releases other minerals -- calcium, magnesium and phosphorous -- which are fertilisers to trees. The fertilisers are washed out of the soil, leaving the soil depleted of nutrients.

Little said these findings are worrying and yet the US Forest Service seems to be downplaying their importance. He cited a case in 1991 when the Procter Maple Research Centre at the University of Vermont pinpointed acid rain and other air pollutants as the causes of decline of sugar maples in Vermont. "We think we are looking at the early stages of an epidemic problem," the Centre's report said.

But the following year the U.S. Forest Service issued a report saying that 90% of the sugar maples surveyed were healthy and the overall numbers and volume of sugar maples were increasing.

It turned out that the Forest Service used a tricky way of counting dead trees: only the standing dead were counted, those lying on the ground were not.

Changes in the leadership of the Forest Service in 1992 infused the agency with more candour. A report issued that year said timbre mortality, volume-wise, increased 24 per cent between 1986 and 1991 "in all regions, on all ownerships, and for both hardwoods and softwoods." Hardwoods were particularly affected, specifically in the south where the mortality increase was 37 per cent, it said.