Tropical deforestation has caused a significant share of global carbon emissions and species
losses, but the patterns of land cover over time have rarely been explicitly considered when estimating
these impacts of deforestation [1]. A deforestation event today leads to a time-delayed release of
carbon into the future, either from the eventual decay of forest products or from the decay 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 deforestation 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 Pg, equivalent to five to ten years of global
deforestation, and a species extinction debt of more than 140 bird, mammal and amphibian forestspecific
species, which if paid, would increase the number of 20th Century extinctions in these groups
by 120%. Given the magnitude of these debts, high-profile commitments to reduce emissions and
biodiversity loss are unlikely to be realised without specific actions, including habitat restoration and
targeted interventions for threatened species, which directly address this damaging environmental
legacy.