The FAO Forest Resources Assessment:
A remote sensing survey on forest cover changes 1980-2000
During FRA 1990, FAO carried out a pan-tropical survey of
forest cover changes based on a sample and remote sensing data.
The main objectives of the survey were to complement country
information data and to provide consistent and reliable
detailed information on change processes for the period
1980-1990 at pan-tropical, regional and ecological zone
levels. 117 sampling units covering 10% of the pan-tropical
area were selected. For each of them satellite imagery was
acquired at two points in time close to 1980 and 1990, and
photo-interpreted with particular attention to the
recognition of changes between nine land cover classes.
In the framework of FRA 2000, the same sampling units
were re-visited, adding a third image close to 2000.
It allowed a three-date time series study covering the
period 1980-2000 and an unprecedented assessment of
trends by comparing the two studied periods.
The objectives of the FRA 2000 remote sensing survey were to:
monitor tropical forest cover state and change for the past 20 years, and current change trends at regional and higher levels;
study the dynamics of change in forest cover and identifying causal mechanisms of deforestation;
complement existing country information by providing spatially and temporally consistent data on forest state and change.
The survey provided a number of estimates on forest cover
and forest cover changes at different levels. The most
important results consisted in 10-year transition matrices
describing changes from one class to another from 1990 to 2000.
Each sampling unit was interpreted at three points in time
with imagery acquired as close to the reference years 1980,
1990 and 2000 as possible. The designations T1, T2 and T3
were assigned to imagery corresponding to the data sets
1980, 1990 and 2000 respectively.
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