Table 2

Forest cover changes in the humid tropics from June 1990 to June 1997. All area figures are × 106 ha. The forest class definitions were made according to those applied by the FAO Forest Resource Assessment Exercise (11) using two parameters: tree cover (canopy density within a forest stand) and forest proportion (forest stand density within the mapping unit). An area assigned to one of the forest classes had a forest proportion of more than 40% in which the forest stands have a tree cover of more than 10%. When the forest proportion was at least 70%, the area was considered closed forest if the tree cover was more than 40% and open forest if the tree cover was between 10 and 40%. When the forest proportion was between 40 and 70%,the area was defined as fragmented forest. Plantations and forest regrowth are grouped as nonnatural forest. Referring to the nonforest classes, mosaics were defined as containing a forest proportion between 10 and 40%. Other natural vegetation such as shrub or grassland, but also agricultural land, may have still contained a forest proportion or a tree cover up to 10%. For forest cover calculations, we applied forest cover weights per class as determined by an independent postassessment of the observation site results (8). The total forest cover estimates in 1990 and 1997 were derived by the addition per class of the weighted forest cover areas. Bold figures indicate the total forest cover in 1990 and 1997; underlined figures indicate the unchanged area for each land cover class between the two dates.

19901997Forest classesNonforest classesForest cover in 1990
ClosedOpenFragmentedPlant/regrowMosaicsNaturalAgricultureUnvegetated
Cover weight 100 100 75 100 25 0 0 0 Per class Total
Closed100902.311.24.11.14.63.416.31.1944
ForestOpen1001.7120.62.40.11.21.62.30.2130
classesFragmented751.81.037.80.13.01.03.10.236
Plant/regrow1000.00.10.07.20.10.31.20.19
NonforestMosaics250.90.10.50.1108.53.210.40.631
classesNatural01.00.40.20.34.1377.121.61.40
Agriculture00.60.30.30.32.63.6232.90.60
Unvegetated00.00.00.00.10.00.80.533.70 1150
Forest cover in 1997Per class90813434931000
total 1116