Publications

How old is old growth?

AMC Outdoors, September 2000

By Michele Pavitt

"Old growth" is a term that most people probably associate with the towering redwoods or giant sequoias in northern California. In the East, the term applies to a different sort of forest — broadly, one that looks largely like the original woodlands that covered America in the early 1600s, when the first European settlers arrived. These rare sites exist in their natural state because they have not been significantly disturbed by human action for hundreds of years. But that doesn't mean these areas have never been harvested; often, some early cutting has occurred, but nature has then taken over. The sites are usually made up of mosaics of multiaged trees — some saplings, some mature trees, and some "legacy" trees 150 years old or more. Another clue to identifying eastern old growth is the presence of large dead trees — some standing, called snags, and some rotting on the forest floor, says David Publicover, AMC's forest ecologist.

To the uninitiated, that may sound like a reasonable explanation of the term. But it's not so clear-cut in the world of forest ecology, I've discovered. Robert Leverett, generally considered a guru in the field, has classified competing definitions of "old growth" into four different categories in his writing. Even then he probably didn't include all perspectives on the subject, he says.

"If you get a bunch of [forest ecologists] in a room, we'd probably enjoy the argument but we wouldn't likely come to any agreement," says Leverett. The term "old growth" may have outlived its usefulness, he adds, since the forests are not always identified by age. They are also defined by their "naturalness" — or the extent to which they've been undisturbed by people.

The flap over definitions arises in part because of the varied topography of the East. A good portion of eastern old growth is found at high elevations where thin soils and harsh weather prevent trees from reaching a large size, says Publicover. Those forests don't have much in common with, say, a stream-side stand of 200-year-old hemlocks. It's also been more difficult to identify fragments of old growth in the East simply because tree species here don't grow as big as in the West.

"The tremendous size of the trees [in the West] makes the older forests very visibly distinct from the younger forests," says Leverett, adding that tree-destroying hurricanes, wind storms, and ice storms are far more common in the eastern U.S. The largest trees in an eastern forest might be only 20 to 30 percent larger than the mid sized ones. "That wouldn't even catch the eye of a casual observer," he says. The oldest eastern trees tend to be spruce and hemlock, which can live more than 400 years and grow as tall as 150 feet; some hardwoods live as long as 350 years. In comparison, the redwoods and giant sequoias of California live as long as 3,000 years and can grow to 375 feet tall.