Burnt forest in the Amazon. Photo by: Alexander Lees.
Once habitat is lost or degraded, a species doesn’t just wink out of existence: it takes time, often several generations, before a species vanishes for good. A new study in Science investigates this process, called “extinction debt”, in the Brazilian Amazon and finds that 80-90 percent of the predicted extinctions of birds, amphibians, and mammals have not yet occurred. But, unless urgent action is taken, the debt will be collected, and these species will vanish for good in the next few decades.
“This time delay offers a window of conservation opportunity, during which it is possible to restore habitat or implement alternative measures to safeguard the persistence of species that are otherwise committed to extinction,” the researchers write.
As of 2008, the Brazilian Amazon lost nearly 20 percent of its forest, comprising over 720,000 square kilometers—an area larger than all of Afghanistan. Despite this, many animals are still holding on. Using complex modeling, the researchers predicted how species will fare through 2050 under four deforestation scenarios.
“The future of biodiversity in the Brazilian Amazon currently stands at a critical juncture. Under business as usual, the Amazon will continue to collect extinction debt for decades to come. On the other hand, with an ambitious program of basinwide conservation investment, the Brazilian Amazon could enter 2050 with minimal (less than 5 percent) species loss and extinction debt,” the researchers write.
However, the two most optimistic deforestation scenarios—an 80 percent reduction in deforestation by 2020 or deforestation ending for good in the same year—are unlikely to occur according to the researchers due in part to recent changes in Brazilian Forest Code.
The most likely scenario then would see around 5 percent extinctions in birds, mammals, and amphibians by 2050 with an increased extinction debt of around 9 percent in these three groups. In other words, total extinctions eventually mounting to around 14 percent of these family groups in the region.
“The declines in deforestation rates over the period 2005 to 2010 have helped widen the window of conservation opportunity for the highly biodiverse Brazilian Amazon,” the researchers conclude. “Continuing legislative and other land development and conservation choices made in the coming months and years will accordingly widen or narrow this window.”
It should be noted that insects, which make up the bulk of biodiversity in the Amazon, were not included in the study—neither were reptiles, fish, plants, of fungi—because scientists simply know too little about the number of these species and their distribution, yet it’s important to note that many of extinctions in the Amazon may be hidden, i.e. species vanishing that have not even been discovered yet by scientists.
CITATION: Oliver R. Wearn, Daniel C. Reuman, Robert M. Ewers. Extinction Debt and Windows of Conservation Opportunity in the Brazilian Amazon. Science. Vol 337. 2012.
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