WHEN the first national parks in the United States were laid out late in the 19th century, they were conceived as islands of natural beauty to be preserved for future generations. Today, it is increasingly clear they are no longer islands, and never really were. What surrounds a park, national monument, or recreational area is as important to its preservation as what's in it. Many parks are pounded by outside influences - timber operations, water pollution, residential and resort development. More subtle influences impinge, too, such as changes in the composition and temperature of the atmosphere.
These enveloping threats will be a primary concern of the new, Bush-appointed leadership of the National Park Service. The parks will remain an invaluable recreational resource for Americans, but their managers will have to strike a better balance between serving visitors and preserving natural resources.
This need prompted the National Commission on Research and Resource Management in the national park system to call recently for a shift toward ``ecosystem management.''
Words like ``ecosystem'' may cause some eyes to glaze over. But the concept is solid. It's a matter of understanding and monitoring nature - so when a species dwindles and disappears, for instance, you know what to make of it. Or as a veteran follower of national-park issues observed, ``How do you know what to protect if you don't know what's there?''
This is particularly pertinent to the 54 million newest acres of park land in Alaska. But it has applications in every park. The complex relationships of plants, animals, and humans are only beginning to be grasped.
If it's to live up to its mandate, the Park Service needs more people and resources devoted to scientific research. A small start has been made. For instance, Glacier National Park has hired the park system's first ecosystem manager. Officials at the Everglades in Florida and at Yellowstone in Wyoming are looking for ways to control the use of ecologically vital areas surrounding their parks.
Increased federal land purchases are another part of the picture. More land insulates parks from development and helps accommodate movement of wildlife. Congress is considering legislation to set up an American Heritage Trust that would allow spending for purchases of new park land to go well above the $206 million set by the Reagan administration.
We all know the budget is tight. But most Americans put a high value on their country's natural heritage. Money for extra land or increased scientific research would be well spent. And if the money is not readily available from public coffers, especially to fund needed research, the millions who use the parks each year should be encouraged to contribute their dollars voluntarily.
The time to start establishing a policy of long-range preservation of park land is now.