The authors point out that even when there's technically no net deforestation, tropical forests can still suffer. For example, if degraded natural forests are replaced by plantations of invasive exotic trees or low water-use efficiency trees, biodiversity will diminish, wildlife could suffer and soil erosion could render streams unusable by local villagers.
"When you save a forest from deforestation, it's great, but you might not have gotten the full package of what you wanted," he said.
The discussion, Putz said, needs to center on the definition of "forest." The Food and Agricultural Organization of the United Nations describes it as an area of more than 0.5 hectares, or a little more than an acre, with trees taller than about 16 feet and more than 10 percent canopy cover. Using that definition could obscure great losses of forest values, he said.
In general, the benefits of a forest are jeopardized when land-use decisions are based on that overly loose classification, according to the paper.
Under that designation, for example, tree plantations qualify as forests. Although plantations can supply services to society such as slope stabilization, firewood and carbon, they can also result in avoidable losses of biodiversity. They have less value in some ways, Putz said, and more value in others.
But once people differentiate among types of forests, alternatives to environmentally destructive management will become real options. Then, decision-makers can fully examine the local, regional and global benefits of natural forests versus their economic priorities.
"We need to demand clarity about what's meant by 'forest' and what the full range of costs are of different interventions," Putz said. "Then we need to figure out the mechanism to get decision-makers to employ the interventions that are least damaging to naturalness but that still satisfy their other desires."
|Contact: Francis E. Putz|
University of Florida