U.S. experts Monday pleaded for boosted efforts to protect tropical forests, which are key to ensuring biodiversity and fighting climate change but are increasingly threatened by deforestation.

“I am gravely concerned about what is happening with tropical forests,” William Laurance, a researcher with the Smithsonian Tropical Research Institute in Panama told AFP.

“There is a very high rate of destruction of the old growth, ancient forests.”

He said the equivalent of 50 football pitches of virgin rainforest was being destroyed every minute amid global warming, large scale habitat fragmentation, and changes in rainfall.

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Intense hunting in areas of the tropics was also leading to the disappearance of “hundreds of species of amphibians,” he said.

“Now we have synergy among those different threats,” Laurance said.

“So when you talk about global warming for example because it’s getting hotter, species in the tropics, where it’s possible, will naturally try to move up to higher elevations where it’s a little bit cooler.

“In many cases they will be trapped by habitat construction, cattle pass, degraded lands,” he warned.

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Laurance is one of the authors of a report presented Monday to a conference organized in Washington by the Smithsonian Natural History museum.

“Indonesia is now in terrible shape, losing more than two million hectares (4.9 million acres) of forest per year. Borneo is being devastated,” he said.

More than half of the planet’s 20 million square kilometers (eight million square miles) of rainforests has already been cleared for human use, while another five million square kilometers (two million square miles) has been selectively logged, said Greg Asner from the Carnegie Institution.

But he said major swathes of land, or some 350,000 square kilometers (140,000 square miles), have been abandoned by human inhabitants and are beginning to grow back.

“Moreover, the regrowth is relatively quick. The forest canopy closes after just 15 years. After 20 years, about half of the original biomass weight has grown back,” he said.