Edinburgh scientist offers hope on climate change

AN EDINBURGH academic has been involved in scientific reports which reveal climate change may have been slowed by an increase in the growth rate of trees in the Amazon rainforests.

But although the growth rate of trees in pristine rainforests has nearly doubled in recent decades, the death rate of those forests has also accelerated, according to reports in a British scientific journal.

In an issue devoted to tropical rainforests, the Proceedings of the Royal Society carries 17 reports from scientists in many countries, from Britain, Italy and Germany to Brazil, Peru and the United States.

In three of the papers, scientists report that in areas of unspoiled Amazon forest, both the growth rate and the death rate are increasing.

Yadvinder Malhi, of the University of Edinburgh, is a contributing scientist and one of the publication’s editors. He said the change in these pristine areas - making up more than half of the Amazon rainforests - may have acted as a brake on global warming.

But Oliver Phillip, of the University of Leeds, one of the contributing scientists and co-editor of the publication, said computer model simulations suggest the benefits cannot be taken for granted.

"The process could be reversed in as short a space of time as the next two decades, by the combined effects of deforestation and global warming," he said.

The scientists report that tropical forests globally have warmed by half a degree Celsius (0.9F) in the past 20 years. That is expected to increase by 3C to 8C (5.4F to 14.4F) by the end of the century, they say.

Mr Malhi said the scientists have no idea of the upper threshold of the trees’ temperature tolerance.

They may not be able to survive the heat, and if the forest dies back, the brake on global warming goes too.

Several papers in the issue debate the possible cause of the growth changes.

The most likely causes are identified as increases in atmospheric concentrations of carbon dioxide and surface air temperatures, and possible continent-wide changes in sunshine.

While pristine rainforests in the Amazon Basin are increasing in biomass, others appear to be breaking up under a combination of climatic and human pressure.

Selective logging punctures the forest canopy and allows sunlight to penetrate to the forest floor, Mr Malhi said, drying it out and making it much more vulnerable to fire.