New satellite-based analysis of forest cover in the humid tropics from 1990 to 2010 contradicts previous estimates of rate of loss.

The road to tracking changes in forest cover in the tropics has been bumpy. Although tropical deforestation was the most egregious man-made source of greenhouse gas emissions in the 1990s, statistics on modifications to forest area in this region before 2000 have been shaky.

Critics have lambasted the United Nations Food and Agriculture Organization (FAO) Forest Resources Assessment (FRA) for incorrectly estimating deforestation rates in the 1980s and 1990s, which was especially true in the tropics, where FRA reported that deforestation rates declined between the 1980s and 1990s. Satellite-based data suggested otherwise. This inaccurate assessment was due, in part, to FRA’s inconsistent definitions of forest and a reliance on national self-reporting.

Now prodigious advances in data availability and processing power have allowed high-resolution assessments of national and global forest cover change, all thanks to long-term archives of satellite imagery. Kim et al. have performed the first pantropical assessment of changing deforestation rates in 34 tropical countries across 2 decades, and their conclusions are grim.

After analyzing 5444 Landsat scenes from the Global Land Survey collection, taken between 1990 and 2010, with a consistent definition of forest cover, the team calculated that deforestation rates in the humid tropical forests accelerated by a whopping 62% from the 1990s to the 2000s. This rate was largely influenced by increased forest loss in tropical Latin America. This flies in the face of the FAO FRA estimates, which reported a 25% reduction of total deforestation rates in the same regions during the same time period.

Despite slow and steady global gains from 1990 to 2000, 2000 to 2005, and 2005 to 2010, the team reports, forest cover in these regions experienced significant losses between 2000 and 2005, which negated any previous gains. Overall, this analysis suggests that deforestation rates in the humid tropical forests underwent an acceleration from the 1990s to 2000s, rather than a deceleration as previously reported by FRA. (Geophysical Research Letters, doi:10.1002/2014GL062777, 2015)

—Julia Calderone, Freelance Writer

Citation: Calderone, J. (2015), Tropical deforestation accelerated faster than initially thought, Eos, 96, doi:10.1029/2015EO037979. Published on 27 October 2015.