DURHAM, N.C. -- A scientific study shows that, eight years after their marketable timber was logged, parcels of Indonesian rain forest contained levels of tree species diversity comparable to those measured in nearby unlogged forest land.
"These results go against a lot of popular dogma," said Charles Cannon, a Duke University doctoral student in botany who is lead author of a report on the work to be published in the Aug. 28 issue of the journal Science.
"The results to me are very preliminary, but I think the main point to take from this is that logged forests are not necessarily destroyed," Cannon said in an interview at Duke. "If they're selectively logged in one cut, there is a great deal of disturbance and damage. But the forests are more resilient than perhaps people have given them credit for.
"This is not pro-logging," he added. "It's not saying that forests are going to be improved upon by logging. And it's not saying that logging doesn't need to be carefully controlled and managed well."
The Science report was co-authored by David Peart, an associate professor in biological sciences at Dartmouth College, and Mark Leighton, director of the Laboratory of Tropical Forest Ecology at Harvard University's Peabody Museum. Funding for the research described in the Science report came from the Conservation, Food and Health Foundation Inc., and the U.S. Agency for International Development.
Both Peart and Leighton were involved in the study's design. And the sampling method used was modeled after one Leighton devised for his own field research site at Gunung Palung National Park.
That park, in Indonesian Borneo, is close to where Cannon collected his tree data in the early 1990s within a lowland forest that had been logged of commercial tree species, mostly three types of Philippine mahogany.
"Everyone talks about logging in such tropical forests, but there is surprisingly little information about what happens to them after they're logged, particularly in Asia," said Cannon, who had graduated from Harvard with a bachelor's degree in biological anthropology in 1989.
To fill that gap, Cannon and his co-authors selected sites that had been "selectively" logged -- meaning harvested of commercially desirable trees above a certain size -- either one or eight years before.
The logged sites also were intermixed with areas that had not been previously harvested because they were inaccessible to heavy machinery or otherwise not worth the loggers' time. That proximity of undisturbed and disturbed areas let the researchers assess the overall impacts caused by logging.
Indonesian government rules, which Cannon noted are not rigorously enforced, restrict logging activities to trees at least 50 centimeters (about 1.6 feet) in diameter as measured at chest height. Thinking ahead to the next generation, Cannon, with help from his co-authors, decided to do detailed inventories of smaller trees, between 20 and 30 centimeters in diameter, at the study sites.
Their rationale was that the young would be the ones robust enough to eventually fill the gaps created by felled timber and the damage of harvesting machinery, as well as produce the seeds that would regenerate the area, Cannon said.
Detailed comparisons showed that areas logged just a year before had 43 percent fewer different species of these smaller trees than did unlogged sites. But the picture was far different at sites that had been given eight years to recover from logging.
Overall, the "species richness of small trees in the eight-year logged site approached that of unlogged forest," said their Science report, which also acknowledged that the reason for this is unclear.
It is important to emphasize that these sites "are not going to recover to their former natural state," Cannon added in his interview. "They've changed." In fact, the study notes that logging seemed to increase the numbers of a commercial camphor tree family that produces wood as well as edible fruits and seeds.
Studying such disturbed forests, in addition to places like Gunung Palung National Park, is crucial, Cannon argued. "We should not just focus our resources and energy on pristine forests that have not been tampered with in any way, because those areas are probably not going to be large enough to maintain populations of plants and animals in the future.
"We also need to know more about the areas surrounding these protected forests and investigate their conservation potentials," he said.
Dartmouth's Peart added: "If our results hold up to further testing, logged forests may be our best, indeed our only opportunity for effective conservation of tropical diversity. Logged forest could be the key to keeping many of Earth's species alive as the human population reaches its peak over the next several decades."
Since 1994, Cannon has been a Duke graduate student pursuing a Ph.D. in systematics, an older academic field of plant and animal classification that has recently been revitalized by the tools of molecular biology.
Note to editors: Charles Cannon can be reached by e-mail at