Amazon rainfall projections ‘underestimated’

Amazonian forests may be less vulnerable to dying off from global warming than feared because many projections underestimate rainfall, Reuters reports.

A study by UK researchers suggested that Brazil and other nations in the region would also have to act to help avert any irreversible drying of the eastern Amazon, the region most at risk from climate change, deforestation and fires.

“The rainfall regime in eastern Amazonia is likely to shift over the 21st Century in a direction that favours more seasonal forests rather than savannah,” the team write in the journal Proceedings of the National Academy of Sciences.

Seasonal forests have wet and dry seasons rather than the current rainforest, which is permanently drenched.

It is argued that this shift in precipitation patterns could result in the emergence of new species of trees, other plants and animals.

The findings challenge past projections that the Amazon forest could die and be replaced by savannah.

The Intergovernmental Panel on Climate Change reported in 2007: “By mid-century, increases in temperature and associated decreases in soil water are projected to lead to gradual replacement of tropical forest by savannah in eastern Amazonia.”

The new study said that almost all of 19 global climate models underestimated rainfall in the world’s biggest tropical forest.

Lowland forests in the Amazon have annual average rainfall of 2,400 mm (94 inches), it said.

Projected cuts in rainfall meant the region would still be wet enough to sustain a forest.

The experts also examined field studies of how the Amazon might react to drying.

It said that seasonal forests would be more resilient to the occasional drought but more vulnerable to fires than the current rainforest.

“The fundamental way to minimise the risk of Amazon dieback is to control greenhouse gas emissions globally, particularly from fossil fuel combustion in the developed world and Asia,” said Yadvinder Malhi, the lead author from Oxford University.

But he said that governments led by Brazil also needed to improve their forest management policies.

Global warming is “accompanied by an unprecedented intensity of direct pressure on the tropical forests through logging, deforestation, fragmentation, and fire use,” the scientists wrote.

And fires, including those touched off by lightning, were more likely to cause wide damage to forests already fragmented by roads or by farmers clearing land to plant crops, such as soya beans.

Source: Reuters

Date: 09/02/2009

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