Traditional land-use systems and patterns of forest fragmentation in the highlands of Chiapas, Mexico

The influence of slash-and-burn agriculture and tree extraction on the spat ial and temporal pattern of forest fragmentation in two municipalities in t he highlands of Chiapas, Mexico was analyzed. The data series were derived from two subsets of satellite images taken in 1974 and 1996. The analysis w as based on area, edge, shape, core area, and neighbor indices. During the 22 years, the dense forest decreased by 8.9%/yr in Huistan and by 8.6%/yr i n Chanal, while open/disturbed forest, secondary vegetation, and developed area increased in both municipalities. The total number of fragments increa sed by 1.4%/yr and 2.3%/yr in Huistan and Chanal, respectively. Dense fores t showed the highest increase in the number of fragments (6%/yr in Huistan and 12%/yr in Chanal), while edge length, core area, and number of dense fo rest core areas decreased. The larger fragments of dense forest present in 1974 were divided into smaller fragments in 1996; at the same time, they ex perienced a process of degradation toward open/disturbed forest and seconda ry vegetation. Two different fragmentation patterns could be distinguished based on agricultural or forestry activities. Forest fragmentation did not occur as a continuous process; the pattern and degree of fragmentation were functions of land tenure, environmental conditions, and productive activit ies. The prevalence of rather poor soil conditions, small-holdings, growing human population densities, increasing poverty, and the absence of alterna tive economic options will maintain a high rate of deforestation and forest fragmentation in the studied region.