The main objectives of the present assessment were: (i) to provide reliable and globally consistent information on the state of the tropical forests by 1990 and the rates of change during 1981 to 1990 and (ii) to undertake studies on the process of deforestation and forest degradation and their environmental implications.

This issue of Unasylva focuses on the recently completed FAO assessment of forest resources at a global level, with 1990 taken as the reference year (a similar assessment was undertaken a decade ago). The articles presented in this issue consider the data generated in the assessment as well as some of the difficult underlying questions inherent in forest resource assessment.

In the context of developing a practicable and cost effective method for obtaining a country’s forest area by remote sensing, the computer processing of NOAA AVHRR HRPT data covering Liberia was investigated. The only cloud-free scene then recorded turned out to be severely and unevenly affected by atmospheric haze. To mitigate the effects of this, the country was divided into six areas (strata) of more uniform haze conditions.