In a park that consists of a complicated mosaic of private and public holdings, they said, erosion and logging-road construction on private land could damage wetlands, streams and forests on public lands.

Airborne heavy metals may also damage high-elevation forests in the northeastern United States.

Canada contends that acid rain from the United States is damaging its lakes and forests, and wants Washington to act to reduce the damage.

Possums are perceived as the major animal pest since they damage native forests and endanger cattle production through the spread of bovine tuberculosis.

Fumes from diesel trucks are important contributors to smog, which plagues New York City, and acid rain, which damages lakes and forests in the Adirondacks.

The buildup in the environment of these acids can damage aquatic life, forests and buildings.

Skin Cancer Threat As the ozone shield thins, increased radiation from the sun is expected to cause more skin cancer and other health problems in humans, and to damage marine life, crops and forests.

But environmentalists fear that unfettered logging could damage virgin forests and the habitat of rare species in the vast Siberian wilderness.

The yellow smoke has damaged forests for hundreds of miles around.

Such radiation has been found to be a cause of skin cancer and to produce other health problems as well as to damage crops and forests.