The revival of the American chestnut could catalyze the first large-scale success in restoration ecology, which aims to bring entire ecosystems to working health. This branch of ecology, still young, differs from movements such as permaculture, which encourages people to devise strategies to make healthy ecosystems flourish and endure. (Like sustainable agriculture, with which it overlaps, permaculture looks for ways to let people live off the land without fundamentally altering it.) Restoration ecologists have looked to ruined ecosystems such as strip-mined land and watersheds wrecked by logging—challenges requiring help from governments and landowners, who usually don't want to give it. Restoring the chestnut forest is a more straightforward goal.
The chestnut was the challenge facing early-twentieth-century American botanists. For decades, however, chestnut blight, which kills by girdling the tree with cankers that work inward and choke off its food supply, resisted all attempts to keep it in check or circumvent it. Because the fungus that causes it lives in the bark of other trees, such as oak and ash, without killing them, the blight still thrives in the chestnut's original range, killing off chestnut seedlings as they reach maturity. (Blight doesn't affect the root system; seedlings grow on stumps, sometimes for several years, before blight fells them.) Researchers crossed the blight-resistant Asian chestnut trees with American chestnuts and then, in classic fashion, crossed resulting generations, too, with Asian chestnuts, in order to introduce as many Asian genes as possible; no one knew which genes or how many conferred resistance. The work was terribly slow: it takes three to five years to prove that a cross is blight resistant. The crosses seemed certain to look like Asian trees, which are far shorter than the American species and shaped differently. And every cross failed. The intensive efforts that had begun in the 1920s petered out in the 1960s.
In the late 1970s Charles Burnham, a well-known plant geneticist, offered fresh hope. He hypothesized that blight resistance could be conferred by crossing American-Asian hybrids in the opposite direction—to American rather than Asian chestnuts, continually diluting out most Asian genes except those few that carried blight resistance. Burnham began working to create a blight-resistant tree that would preserve many more American characteristics, collaborating with Philip Rutter, a biologist and ecologist who was already trying similar breeding experiments.
The goal suddenly seemed decades, not centuries, away. The federal government had ended the chestnut program it had sponsored since the 1930s, so a group of independent researchers who had been seized by the chestnut dream formed the American Chestnut Foundation in 1983, with the grandiose aim of repopulating the Appalachians with American chestnuts. The smaller nuts of a true American chestnut, or something as close to it as possible, might not bring as high a price as the Asian chestnuts under commercial cultivation in California—but the benefits to wildlife populations would be incalculable. The oaks that took the place of chestnuts in many areas produce acorns irregularly, whereas chestnuts drop huge crops of easy-to-eat nuts year after year. The forests would benefit too. Rutter, who served as the foundation's president for ten years, estimates that a forest dominated by chestnut trees grows 30 percent faster than one dominated by oaks; the hyperactive chestnut produces sugar from sunlight all winter, staying bright green beneath its thin bark year-round. Also, the chestnut is a gorgeous tree.