XVI International Botanical Congess

Variations in geographical cover for different types of ecosystems recorded in Mexico are presented in this work. Habitat loss and ecosystem fragmentation were analyzed comparing the land use and vegetation maps obtained by INEGI during 1973 and 1993. Ecosystem types were grouped in 37 classes including natural ecosystems (36) and one class for modified ecosystems which included agroforestry and grazing land uses. Results show that during the last 20 years, 28 types of ecosystems have diminished considerably. The desert ecosystems such as the microphyllous desert, the Tamaulipan thorn scrub and the mesquite forests, as well as the tropical rain forest, inland freshwater ponds and oak forests are presently the ecosystems facing major threats. These record a geographical contraction ranging between 5,000 and 15,000 km2 of their recorded surface for 1973.