Mongabay - Fragmented Tropical Forests Significantly Drier Than Intact Areas

[hatrack]

A new study in Biological Conservation has shown that edge forests and forest patches are more vulnerable to burning because they are drier than intact forests. Using eight years of satellite imagery over East Amazonia, the researchers found that desiccation (extreme dryness) penetrated anywhere from 1 to 3 kilometers into forests depending on the level of fragmentation.

"Fire is one of the biggest threats to the world's tropical forests, but in general, rainforests will not burn because they are too moist. But logged forests and edge forest can burn," tropical ecologist Susan Laurance, one of the study's authors, told mongabay.com. "We now think we understand why this happens. During the dry season these forests near the edge are drying out increasing their vulnerability to fires, whereas intact rainforests do not dry out over the same period."

The study also found that the age of the deforestation and fragmentation made a difference. Younger edge forests were drier, and thereby more prone to fire, than older edge forests where new trees and plants have begun to grow back perhaps protecting the forests from desiccating winds.

To the question of why fragmented and edge forests are drier than intact forests, Laurance admits: "we do not know for sure." But she adds "we suspect it could be the water table and local climate conditions such as low humidity, increased drying winds, or perhaps even a decline in rainfall." Laurance says the study may point to even larger to date unrecognized impacts happening in edge forests: " suggests that deforestation along the eastern Amazon frontier is influencing local weather but we do not have direct evidence for this and there are so few weather stations in the region there is not any data to say for sure."

EDIT

http://news.mongabay.com/2010/1013-hance_fragmented_dry.html