Evaluaciones de recursos forestales mundiales

FRA 1990 and 2000 Pan-Tropical Remote Sensing Surveys

The first FRA remote sensing survey was implemented as part of FRA 1990, aiming at complementing the assessment based on country information by providing consistent and quality-controlled estimates of forest cover and change of the pan-tropical region. The survey relied on statistical sampling (10 %) of the world's tropical forests through 117 sample units located throughout the Pantropical zone, representing 87 percent of the world’s tropical forests. Each sample unit consisted of multi-date Landsat satellite images which provided the raw material for producing statistics on forest and other land cover changes from 1980 to 1990. The survey produced estimates of state and change at regional, ecological and pan-tropical levels but not at the national level.

The FRA 2000 pan-tropical remote sensing survey built on the FRA 1990 survey, and complemented the sample units with more recent Landsat satellite images in order to assess forest and land cover changes for both the period 1980 to 1990 and 1990 to 2000.

Important products generated through these surveys include change matrices for the tropics as a whole (developing country areas) and for Africa, Asia and Latin America separately. The matrices the various forest and land cover classes and how they have changed over the past two decades, and for the first time a consistent methodology was used for assessing forest cover change between two assessment periods (1980 to 1990 and 1990 to 2000). Correlations between the remote sensing survey results and the country statistical data for the tropics summed at regional levels were good, although the remote sensing survey indicated a lower level of deforestation than the aggregate national findings for Africa.

Results of these surveys at the pan-tropical level indicate that the world's tropical forests within the surveyed area were lost at the rate of about 8.6 million hectares annually in the 1990s, compared to a loss of around 9.2 million hectares during the previous decade. While this change fell within the margin of error for the tropics as a whole, statistically significant decreases in deforestation were detected in tropical moist deciduous forests. In contrast, smaller increases in deforestation (not statistically significant) were detected in both tropical rain forests and dry forests. Across the tropics, most of the deforestation was due to the direct conversion of forests to permanent agriculture or pastures and, to a lesser degree, to the gradual intensification of shifting agriculture.

Key outputs

Forest resources assessment 1990. Survey of tropical forest cover and study of change processes
FRA 2000 Main Report