Amazon River in Peru falls to second lowest level on record
September 4, 2007
The news comes as worries mount that the Amazon rainforest will face another dry year like that of 2005 when river commerce came to a standstill, stranding remote communities and leading parts of Brazil and Peru to declare states of emergency.
While variable water levels are characteristic of the Amazon river ecosystem, the increasingly extreme fluctuations are of great concern. Officials fear that low water problems will only worsen in coming years as more forest is cleared, glaciers in the Andes continue to retreat, and the Amazon continues to dry due to climate shifts.
"There are several other factors that are pushing the Amazon towards a drier future, including fresh evidence that cattle ranches and pastures are less capable of generating rain than the forests they replace because they put less water vapor into the air," said Dr. Daniel Nepstad, a researcher at the Woods Hole Research Center and one of the world's foremost experts on the Amazon rainforest. "On top of these changes in the vegetation itself we have rainfall-inhibiting smoke and the prospect of sea temperature changes--not just el Niņo which we have always known creates drought in the Amazon--but the North Atlantic tropical anomaly like we saw in 2005 when we had record drought and record fires in the Amazon. The likelihood of that type of anomaly will increase with global warming. If we start to see sea surface temperature anomalies more frequently--either el Niņo or the warming of the tropical North Atlantic (that occurred in 2005)--then the area of tropical forest that burns could explode."
"The nightmare scenario is one where we have a 2005-like year that extended for a couple years, coupled with a high deforestation where we get huge areas of burning, which would produce smoke that would further reduce rainfall, worsening the cycle," Nepstad continued. "A situation like this is very possible. While some climate modelers point to the end of the century for such a scenario, our own field evidence coupled with aggregated modeling suggests there could be such a dieback within two decades."
2007 is shaping up to be a similar year to 2005 with warming in the tropical North Atlantic (the same conditions that influence hurricane formation in the Caribbean and East Coast of the United States). Another year of drought is of great concern to researchers studying the Amazon ecosystem. Field studies by the Woods Hole Research Center suggest that Amazon forest ecosystems may not withstand more than two consecutive years of drought without starting to break down. Severe drought weakens forest trees and dries leaf litter leaving forests susceptible to land-clearing fires, which, in turn, produce smoke that hinders the formation of rain clouds. Logging and deforestation only worsen the effects, which can lead to a feedback cycle that further dries the forest.
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