“Cutting down trees doesn’t kill a bird directly. It takes a lot of time for those birds to actually die. They’re all crammed into the habitat that’s left. Then gradually you’ll have this increased mortality,” explains Robert Ewers, an ecologist at Imperial College London and the study’s lead author.
The deaths of species over a few generations, instead of as an immediate reaction to changes, leads to an ‘extinction debt’ that will, unfortunately, be paid in full. By some estimates, 80 percent of extinctions in the Amazon are still impending due to the damage that’s already been done and species are expected to continue to go extinct for decades even if deforestation is stopped.
The researchers who completed the study examined what would happen in the future with four scenarios: “‘business as usual’, or little regulation; ‘governance’, or some regulation; ‘strong’, or reducing deforestation by 80 percent by 2020, in accordance with the Brazilian government’s goal; and ‘end of deforestation’ by 2020.”
If development continues at the current ‘business as usual’ rate, between 80 and 90 percent of predicted extinctions will happen over the next 40 years. According to Ewers, “that will add up to an estimated 40 to 50 species of birds, mammals and amphibians that will likely go extinct by 2050 and another 100 expected to be lost after that.”
“For now, the problem is along the arc of deforestation in the south and east where there is a long history of forest loss. But that is going to move in the future. We expect most of the species there to go extinct, and we’ll pick up more extinction debt along the big, paved highways which are now cutting into the heart of the Amazon,” Ewers told the Guardian.
The good news, according to the study, is that there is a window of opportunity to concentrate conservation efforts in the areas with the greatest debt.
“I think this is good news, I think it’s really good news,” said Thiago Rangel, an ecologist and biogeographer at the Federal University of Goiás in Brazil. “First, deforestation in Amazonia has not been as huge as we expected about 10 years ago. Second, there’s still time to prevent local extinctions as a consequence of accumulating deforestation over the last 30 years. There’s still time to start implementing conservation strategies to prevent these local extinctions.”
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