Extinction Debt and Windows of Conservation Opportunity in the Brazilian Amazon

Growing Extinction Debt Predicting, and potentially preventing, extinction is a central goal of conservation biology. Wearn et al. (p. 228; see the Perspective by Rangel) describe a mathematical approach for predicting the time lags in extinction following habitat loss. The model was applied to the highly biodiverse Brazilian Amazon region, and used to reconstruct the spatial and temporal patterns of extinction and the accumulation of extinction debt from 1970 through to the present, and to extrapolate to 2050 under four deforestation scenarios. The Amazon basin sits at a critical point: Few species have been driven extinct to date, but an extinction debt is rapidly accumulating, which could lead to an increasing rate of extinction in the next four decades. Deforestation scenarios predict species extinction rates and identify targets of conservation efforts. Predicting when future species extinctions will occur is necessary for directing conservation investments but has proved difficult. We developed a new method for predicting extinctions over time, accounting for the timing and magnitude of habitat loss. We applied this to the Brazilian Amazon, predicting that local extinctions of forest-dependent vertebrate species have thus far been minimal (1% of species by 2008), with more than 80% of extinctions expected to be incurred from historical habitat loss still to come. Realistic deforestation scenarios suggest that local regions will lose an average of nine vertebrate species and have a further 16 committed to extinction by 2050. There is a window of opportunity to dilute the legacy of historical deforestation by concentrating conservation efforts in areas with greatest debt.