|Cloud Forests in the Humid Tropics: A Bibliographic Review (UNU, 1987, 81 pages)|
|2. Cloud forest distribution in the humid tropics|
The following is an attempt to determine the extent of the principal areas of cloud forests in the humid tropics within the zone defined in the introduction (see figure 1). Boekor (1979) estimates the total surface of cloud forests in the humid tropics at 500,000 km2 which would be equivalent to approximately 10% of the existing "tropical rain forest" according to Persson (1974) and would correspond, for example, to the total area of Kenya or Thailand.
Given that the occurrence of cloud forests is strongly linked to geographic and climatic factors, different sources are used to define the distribution of the cloud forests and indicate their limits in a general fashion in figure 6. The principal references used are: Martin (1955), Schweinfurth (1957), Lauer (1968), Wiebecke (1971), Paijchmans (1975) and IUCN (1982).
It is important to mention here that figure 6 is only an attempt to give a general idea of the geographic distribution of cloud forests in the humid tropics, due to considerations of scale and to lack of sufficient secondary information for the African and Asian tropics. For this reason figure 7, which shows the contiguous distribution of the Cyatheaceae according to Kroener (1968), is added for comparative purposes and as an additional indicator. As already mentioned in chapter 1, various authors indicated that the presence of Cyatheaceae was typical of tropical cloud forests. Comparing the two maps (figures 6 and 7), one can observe that in the humid tropics the distribution of cloud forests coincides, to a very great degree, with the contiguous distribution of the Cyatheaeeae.