National assessment of the fragmentation, accessibility and anthropogenic pressure on the forests in Mexico

Forest managers and policy makers increasingly demand to have access to estimates of forest fragmentation,human accessibility to forest areas and levels of anthropogenic pressure on the remaining forests to integrate them into monitoring systems,management and conservation plans.Forest fragmentation is defined as the breaking up of a forest unit,where the number of patches and the amount of expose edge increase while the amount of core area decreases.Forest fragmentation studies in Mexico have been limited to local or regional levels and have concentrated only on specific forest types.This paper presents an assessment of the fragmentation of all forest types at the national level,their effective proximity to anthropogenic influences,and the development of an indicator of anthropogenic pressure on the forests areas.Broadleaf forests,tropical evergreen forests and tropical dry deciduous forests show the greatest fragmentation.Almost half(47%) of the tropical forests are in close effective proximity to anthropogenic influences and only 12% of their area can be considered isolated from anthropogenic influences.The values for the temperate forests are 23% and 29% respectively.Anthropogenic pressure in the immediate vicinity of anthropogenic activities is much higher in the tropical forests(75 in a scale 0-100) than in the temperate forests(30).When considering these results jointly,the tropical forests,and more specifically,the tropical evergreen forests and tropical dry deciduous forests are under the greatest pressure and risks of degradation.