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Peering into the future with scientific arson

Scientists are setting fires in the Amazon to figure out how encroaching agriculture and climate change will affect forests.

A fire burns in the Amazon. (Courtesy Jennifer Balch)

ROME — Scientists will set fire later this month to a small patch of the Amazon forest. A line of flames will crawl across the leaf-covered ground, rip through patches of dry grass and linger over fallen logs — the victims of blazes from previous years.

Following in the fire's wake will be a phalanx of researchers, measuring temperature and humidity, trying to understand how the forest burns. “The flames are about knee-high,” said Jennifer Balch, who is  the scientist coordinating the blaze for Massachusetts’ Woods Hole Research Center and the Amazon Institute for Environmental Research. “We can actually move around and jump over them. So far, nobody has gotten singed, but by the end of it we’re definitely done with smoke and barbecues.”

The act of scientific arson is an attempt to peer into the future of the Amazon as the encroachment of agriculture and the changing of the climate subject the forest to a new array of stresses.

Charcoal layers in sedimentary deposits in lake beds show that the Amazon has burned in the past, but flames swept through only once every century or two. Recently however, fire has come under increasing use as an agricultural tool. It’s commonly used to clear forests or maintain cattle pastures. Since few measures are put in place to contain the blazes, the forest near ranches and farms can be set aflame every few years. The Woods Hole project is located on the southern stretch of the Amazon Basin in what is known as Brazil’s arc of deforestation, where the agricultural frontier meets the forest. Balch and her fellow scientists have been subjecting research plots there to annual fires since 2004. “The idea is to simulate the extreme fire frequency that is happening in the region,” Balch said.

Unlike forest fires in the United States, where flames rage into the treetops, a fire in the Amazon tends to stay confined to the undergrowth. The larger trees survive. Mid-sized ones can be damaged. Smaller trees, such as saplings, succumb to the flames.

Since the project began, the group has noticed that the number of species present in the undergrowth has dropped by half. Most of the survivors are plants that can resprout from underground roots. Some of the damaged trees have died and fallen. The canopy has begun to open.