Geophys. Res. Lett. http://doi.org/3f6 (2015)

Terrestrial ecosystems have taken up about a quarter of anthropogenic CO2 emissions over the last 50 years or so. However, emissions from fire, logging and cropland expansion — collectively known as land-use and land-cover change — offset some of the carbon taken up. Assessment of the amount of carbon released from tropical deforestation relies in part on remotely sensed data from satellites, so quantifying historical deforestation and associated carbon release that predate the satellite era is difficult.

One approach to quantifying the net contribution of anthropogenic land-use change is to estimate the difference between current aboveground biomass and its potential without past human interference. To do this for the Amazon Basin, Jean-Francois Exbrayat and Matthew Williams from the University of Edinburgh, UK, constructed two maps of potential aboveground biomass based on the relationship with climate and topography in intact forest landscapes. Their reconstructions suggest a current deficit of 11.5–12% in aboveground biomass — or a net loss of ∼7-8 PgC — compared with current estimates for the Amazon Basin.