The Environmental Legacy of Modern Tropical Deforestation

Summary

Tropical deforestation has caused a significant share of carbon emissions and species losses, but historical patterns have rarely been explicitly considered when estimating these impacts [ 1]. A deforestation event today leads to a time-delayed future release of carbon, from the eventual decay either of forest products or of slash left at the site [ 2]. Similarly, deforestation often does not result in the immediate loss of species, and communities may exhibit a process of “relaxation” to their new equilibrium over time [ 3]. We used a spatially explicit land cover change model [ 4] to reconstruct the annual rates and spatial patterns of tropical deforestation that occurred between 1950 and 2009 in the Amazon, in the Congo Basin, and across Southeast Asia. Using these patterns, we estimated the resulting gross vegetation carbon emissions [ 2, 5] and species losses over time [ 6]. Importantly, we accounted for the time lags inherent in both the release of carbon and the extinction of species. We show that even if deforestation had completely halted in 2010, time lags ensured there would still be a carbon emissions debt of at least 8.6 petagrams, equivalent to 5–10 years of global deforestation, and an extinction debt of more than 140 bird, mammal, and amphibian forest-specific species, which if paid, would increase the number of 20 ^th-century extinctions in these groups by 120%. Given the magnitude of these debts, commitments to reduce emissions and biodiversity loss are unlikely to be realized without specific actions that directly address this damaging environmental legacy.

Highlights

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  Time lags in historical tropical deforestation ensure an emission debt of 8.6 PgC

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  Tropical deforestation resulted in a debt of more than 140 forest-specific vertebrates

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  The carbon emissions debt is equivalent to 5–10 years of global deforestation

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  The extinction debt would increase 20 ^th-century extinctions in vertebrates by 120%

Abstract

Rosa et al. estimate that historical tropical deforestation has indebted the future with 5–10 years of global deforestation’s worth of carbon emissions and more extinctions than estimated to have already occurred since 1900. Habitat protection alone will do little to avoid paying these debts that have already accumulated from historical habitat loss.