There were four different ecological zone systems used in this study, although three of them were closely related to each other. These systems were:

1. Lavenu, F., M.F. Bellan and C. Meste (1988). Carte ecofloristique de l'Amerique du Sud. FAO, Rome.

2. Sharma, M.K. (1986). Ecofloristic zone and vegetation maps of tropical continental Asia. FAO, Rome.

FAO (1989). Classification and mapping of vegetation types in tropical Asia. FAO, Rome.

3. Sharma, M.K. (1988). Eco-floristic zone map of Africa. FAO, Rome.

4. Holdridge, L.R. (1967). Life zone ecology. Tropical Science Center, San Jose, Costa Rica.

We acknowledge FAO for the use of the FAO ecofloristic zones datasets and IIASA (through GRID) for the use of the Holdridge datasets. The correct reference for the digital version of the latter is:

Leemans, Rik, 1990. Global data sets collected and compiled by the Biosphere Project, Working Paper, IIASA-Laxenburg, Austria.

The regions in this study in which each of these was used were as follows:

These zones were overlaid upon the forests layer so that the analysis could show how much forest of each type was within each ecological zone in each region, and pinpoint unique types more accurately.

The zones systems did not correspond completely in their boundaries to the coasts and inland water bodies of land masses. This created a figure which we have called "excluded forests". These are forests which occurred in a region but were outside of the zones.