Global rates of forest loss – everyone’s a bastard

29 04 2010

© A. Hesse

I’ve written rather a lot about rates of forest loss around the world, including accumulated estimates of tropical forest loss and increasing fragmentation/loss in the boreal forest (see Bradshaw et al. 2009 Front Ecol Evol & Bradshaw et al. 2009 Trends Ecol Evol). For the tropics in particular, we used the index that an area of rain forest about the size of Bangladesh (> 15 million hectares) was disappearing each year, and in Russia alone, annual decline in forest area averaged 1.1 million hectares between 1988 and 1993. Mind boggling, really.

But some of these estimates were a bit old, relied on some imprecise satellite data, and didn’t differentiate forest types well. In addition, many have questioned whether the rates are continuing and which countries are being naughty or nice with respect to forest conservation.

It was great therefore when I came across a new paper in PNAS by Hansen & colleagues entitled Quantification of global gross forest cover loss because it answered many of the latter questions.

Part of the problem in assessing worldwide forest cover loss in the past was the expense of satellite imagery, access problems, data storage and processing issues. Happily, new satellite streams and easing of access has rectified many of these limitations. Hansen & colleagues took advantage of data from the MODIS sensor to create a stratification for forest cover loss. They then used the Landsat ETM+ sensor as the primary data for quantifying gross forest cover loss for the entire planet from 2000 to 2005. They defined ‘forest cover’ as “… 25% or greater canopy closure at the Landsat pixel scale (30-m × 30-m spatial resolution) for trees > 5 m in height”.

For your reading pleasure (and conservation horror), the salient features were: Read the rest of this entry »