Global remote sensing survey

The Food and Agriculture Organization of the United Nations (FAO) is distributing FAO Forest Paper 169 Global forest land-use change 1990–2005 (http://www.fao.org/forestry/fra/remotesensingsurvey/en/). Following are excerpts from the Executive Summary.

“This report presents the key findings on forest land use and land-use change between 1990 and 2005 from FAO’s 2010 Global Forest Resources Assessment (FRA 2010) Remote Sensing Survey. This survey was the result of a partnership between FAO, countries and the European Commission Joint Research Centre (JRC). It is the first report of its kind to present systematic estimates of global forest land use and change.”

“The survey is based on a systematic sample of Landsat satellite imagery for the years 1990, 2000 and 2005 located at the intersection of each degree of longitude and latitude. Globally, 15 779 sample sites were processed for land cover and land use. The final number of sample sites analysed was 13 066 after accounting for sites with no data, statistical outliers and nation-specific review and revision (see Annex 1). The area surveyed at each sample site was 10 km × 10 km, providing a sampling intensity of about 1 percent of the global land surface.”

“This report focuses on forest land use, not land cover. Forest land use is defined as areas with tree cover, or where management or natural processes will ultimately restore tree cover, and the predominant use is forestry. In some cases, forest land use may include land temporarily without tree cover, for example during cycles of shifting cultivation, forest plantations and even-age forest management. This approach is consistent with the forest definition used in FRA country reports and similar to the classes used in national reports under the United Nations Framework Convention on Climate Change.”

“The survey estimates the total area of the world’s forests in 2005 at 3.8 billion hectares, or 30 percent of the global land area.  Overall, there was a net decrease in global forest area of 1.7 percent between 1990 and 2005, at an annual rate of change of 0.11 percent. This equates to an annual shift from forest land use to other land uses of 3 million hectares per year between 1990 and 2000 and of 6 million hectares per year between 2000 and 2005.”

“Major regional differences were found in the net rates of forest area change; only Asia and North America experienced gains in forest area and all other regions saw net losses. South America had the highest net forest loss, losing some 3.3 million hectares annually between 1990 and 2005. Africa had the second highest net forest loss – 1.6 million hectares annually – during the same period. Europe, including the Russian Federation, had a net loss of 0.5 million hectares annually and Oceania lost just under 0.1 million hectares annually. North America experienced a net gain in forest area of 0.2 million hectares annually, while Asia had a net gain of 1.4 million hectares annually between 1990 and 2005.”

“For this survey, forests were categorized according to four climatic domains: boreal, subtropical, temperate and tropical. There were significant gains in forest area in the boreal (0.9 million hectares annually) and subtropical (1.1 million hectares annually) between 1990 and 2005. There was also a net gain in forest area in the temperate domain of 0.9 million hectares annually over the same period.  In contrast, the tropical domain had a net loss of forest area of 6.8 million hectares annually between 1990 and 2005. This net reduction in forest land use was nearly 2.5 times the net forest area gained in the other three domains combined.”