Half of Amazon Forest Being “Profoundly” Damaged

Half of the Amazon rain forest is being damaged by the pollution caused by forest burning, a new study has revealed.

Half of the Amazon rain forest is being damaged by the pollution caused by forest burning, a new study has revealed.

Previous concerns about the world’s largest rain forest have focused on the burning itself, which has now destroyed 14 percent of the forest’s five million square kilometres. But the new research shows that half of the remaining pristine forest is being degraded by the gases and particulates released by the burning.

Paulo Artaxo, who conducted the work with colleagues at the Universidade de SÐo Paulo in Brazil, told New Scientist: “This is causing a profound effect on the health of the ecosystem – there is no doubt about it. “

The pollution caused by burning will also impact on the Amazon forest’s critical role in the global climate, affecting the production of water vapour in the tropics.

Daniel Rosenfeld, at the Hebrew University of Jerusalem, points out that particulate pollution has an immediate impact and is also a concern across the world: “Greenhouse gases will dominate climate change in the long term but we should give similar priority to what happens to climate in this generation as a result of particulate pollution. We have a very different climate to what we would have if we had kept our atmosphere clean.”

Shade and light

Artaxo’s work calculates for the first time the amount of the sunlight absorbed by the pollution caused by forest burning. The 150 Watts/m2 of heat absorption is equivalent to an average cooling on the ground of 3 °C. The average cooling caused by greenhouse gases is less than 3 Watts/m2.

The cooling is produced by tiny aerosol particles in the air which have a very significant effect on photosynthesis. In some places there is 40 percent reduction in the total radiation that would have reached the surface, says Artaxo.

A second effect is the poisoning of vegetation by ozone, a phytotoxic gas produced by burning. Natural levels of ozone are no higher than 15 ppm, says Artaxo, but in affected areas in Amazonia levels are nearly seven times higher. The ozone can travel up to 1500 kilometres from the site of the burning, meaning vast tracts of untainted forest are affected.

“Other studies in China show that ozone pollution has reduced the production of crops by 20 to 25 percent,” he adds.

Amazonia has suffered tremendous land use changes in last 20 years, says Artaxo, but one programme Brazil is currently promoting to tackle the problem is to persuade farmers to cut down forest, not burn it. An additional agricultural benefit of this is that, if the felled vegetation is left on the ground for 12 to 18 months, its nutrients leach into the soil rather than being lost to the air.

This research was presented at the American Association for the Advancement of Science’s 2002 annual meeting in Boston.

Author: Damian Carrington

News Service: New Scientist

URL: http://www.newscientist.com/news/news.jsp?id=ns99991942

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