As deforestation has accelerated in the Brazilian Amazon over the last 40 years, scientists have been watching for an equally rapid rate of extinctions among animals that are losing their habitats.
But so far, no species have disappeared from the region as a whole, and only a small percentage of those predicted to be at risk have gone extinct on a local basis. Instead, there has been a delay between forest loss and species loss, putting the Amazon in debt.
It owes extinctions and nature will come soon to collect.
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Over the next 40 years, found a new study, if deforestation and development occur at their current rate, up to 90 percent of predicted local extinctions will finally occur.
The silver lining is that there may be a window of opportunity for protecting threatened species before they're gone. Conservationist's eyes are now turned to the Brazilian government, whose upcoming rulings about deforestation regulations and development issues will determine whether many species stay or go.
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"While we haven't seen extinctions yet, we're basically just stacking them up for the future -- there is a whole list of extinctions waiting to happen," said Robert Ewers, an ecologist at Imperial College London. "Decisions in the Brazilian congress will have very different futures depending on which whey they go."
Forty percent of the world's tropical rainforest and a large portion of its biodiversity lie in the Brazilian Amazon, which has also borne the brunt of deforestation in the last few decades.
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And while experts have long expressed concerns about the species loss that is sure to follow habitat destruction, until now researchers have not made any hard-number estimates of how many species we can expect to lose in the region as a result of human activities.
To fill in that gap, Ewers and colleagues created a model that took into account rates of deforestation throughout the Brazilian Amazon from the 1970s through 2008. Then, referencing studies that relate habitat loss with losses of mammals, birds and amphibians, they projected future extinction rates through 2050. They also considered four scenarios with varying levels of protection and destruction.
Compared to previous studies that have predicted quick and devastating species loss from deforestation, the researchers report today in the journal Science that extinctions have so far, been happening much more slowly than expected. It can take generations for species to finally reach their tipping points in response to changing conditions.
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But if Brazil proceeds with a "business as usual" scenario, between 80 and 90 percent of predicted extinctions will finally occur over the next 40 years, the study found. That adds up to an estimated 40 to 50 species of birds, mammals and amphibians that will likely go extinct by 2050, Ewers said, and another 100 expected to be lost after that.
Using a grid that considered the Amazon in 50-kilometer (31-mile) by 50-km (31-mile) squares, the researchers were also able to pinpoint regions where species loss is likely to be most extreme. Those results differed depending on which scenario they looked at. And in some cases, certain types of animals fared worse in certain regions.
In an extreme scenario with extra-high levels deforestation, at least 10 species of amphibians, 15 species of mammals and 30 species of birds could disappear from about half of the Amazon.
Such regional detail should prove invaluable for planning conservation efforts.
"Because we can now say exactly which parts of the Amazon are likely to have higher debt," Ewers said, "it means that we can get in there and do conservation actions to save them in those locations."
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With major reductions in deforestation and other protective measures, the study also found that future losses could be reduced by up to two-thirds.
"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."
Now is a critical time to make things right, Rangel added. To counteract economic crisis, the Brazilian government is considering relaxing forest protections and increasing development of power plants and other infrastructure projects. The new study points out how strongly politics can affect the environment.
"We are in a very crucial moment to make the right political decisions about where we are going with Amazonia," Rangel said. "This is a wake-up call."
