Man-induced changes in vegetation cover in the Iztaccíhuatl-Popocatepetl Region

Abstract

An analysis has been carried out on the changes in natural communities in the Iztaccíhuatl-Popocatépetl region in the period 1986 to 1997 using satellite images and vegetation ground data. The ecological impacts of these recent changes are discussed in relation to the increase in human pressure and future hazards. The most obvious changes were observed in the forested parts (2,500 – 4,000 m) of the area. More sparse Pinus hartwegii stands were found at the highest forest sites in 1997 than in 1986; secondly, dense Pinus, Abies or mixed forest decreased in density at the lower slopes. Finally, a large increase in area with shrubs and very sparse tree cover was found in the central-eastern slopes over a large altitudinal gradient. Via cross comparison it became evident that total forest density decreased with 13.2 %, and forest fragmentation increased, too. A detailed cross-comparison showed that the observed deforestation rate is strongly influenced by its accessibility (distance to trails and its steepness). Three main causes have been identified for this decline in forest cover, viz. (a) enhanced frequency of burning, associated with more livestock grazing; (b) more destructive forestry activities, and (c) increased settlements, especially at the eastern part of the region. A considerable part of this high volcanoes region has an increased risk of erosion because of this deforestation. In addition, non-fossil CO₂ emission will strongly increase by the deforestation process. Finally, this gradual degradation may lead to a decline in typical, partly endemic biodiversity in future. It is concluded that adequate natural resource management is highly needed in the near future.