Out of the woodwork

日期:2017-04-05 05:49:06 作者:秋燹掀 阅读:

By Bob Holmes THEY may look tattered and torn, but forests that have been plundered by loggers can still retain most of their tree species diversity. Ecologists studying Southeast Asian forests that have been stripped of their most valuable timber say that the regenerating forest canopy will eventually look much like it did before the trees were felled. This is good news for conservationists, who are unlikely to succeed in getting vast areas of pristine forest set aside as preserves. “Most of the tropical forest that’s left has either been logged or will be logged,” says David Peart, a forest ecologist at Dartmouth College in Hanover, New Hampshire. Ecologists agree that clear-felled forests are unlikely ever to recover, even if the land is not converted to pasture. Most have also assumed that selective logging, in which the most valuable timber is removed, also causes lasting ecological damage. To put this idea to the test, Peart and his colleagues counted and identified all trees with a trunk diameter of 20 centimetres or more on 12 plots each measuring 0.1 hectares, in pristine, unlogged lowland forests of Kalimantan in Indonesia. They repeated the exercise on 12 similar plots that had been logged the previous year, and on nine plots that had been logged seven years before that. Although the loggers had felled only large trees from the most valuable species, they still caused extensive damage, destroying about 40 per cent of all trees on each plot. Even eight years after being plundered, logged plots contained around a third fewer trees than unlogged plots. However, logging seemed to have caused no reduction in tree species diversity. Indeed, the plots logged eight years previously actually contained more species than the pristine plots ( Science, vol 281, p 1366). “Physically, these logged forests look quite devastated,” says Peart. “There’s a tangle of vegetation, and the ground’s chewed up. So the fact that all the species seem to be there after eight years is really quite surprising to me.” This was true even for the smallest trees the researchers sampled, which would have been mere saplings when the loggers went to work, and perhaps especially vulnerable to disturbance. “That means that the little trees have since grown up rather well. That is perhaps the most encouraging thing of all,” says Peart. Some forestry experts have argued for several years that logged forests represent an important opportunity for conservation—not least because they are relatively cheap to buy. Peart’s study provides the first clear confirmation of this idea. “I’m glad somebody’s finally saying it with data,” says Francis Putz of the University of Florida in Gainesville. However, both Peart and Putz warn that this does not mean timber companies should be allowed to log with impunity. No one knows whether forests will survive selective logging equally well in other parts of the world—especially in Latin America, where the pattern of logging can be quite different. And Peart’s study does not measure an indirect effect of logging that may cause the most damage of all in the long term: