164 Miguel Martínez Tapia et al. 11 The Environmental Calculator: A Tool for the Efficient Assessment of Environmental Services Loss due to Deforestation Miguel Martínez Tapia, Xanat Antonio Némiga and José Isabel Juan Pérez Autonomous University of the State of Mexico, Mexico Introduction: Why an Environmental Calculator? Forest ecosystems contribute to protect soils from erosion and to regulate watersheds and local hydrological systems by reducing variation in water flows. They also provide local and global climate regulation, carbon storage as well as air and water purification. Forests contain the largest assortment of species found in any terrestrial ecosystem and supply numerous social and cultural services. They are also part of our cultural and historical heritage (Stenger et al., 2009). Information about forest values might be needed for legal processes of damage compensation, but also for cost-benefit analyses, for the establishment of governmental regulations, for ‘‘environmental pricing’’ or simply for general information (Elsasser et al., 2009). The unavailability of cartographical values, representing differential prices for the economical value of environmental services which forest provides, make it difficult to use such resources on a sustainable basis. One major threat to forest sustainability is deforestation. Deforestation has several side effects on the ecosystem services of a site. As runoff and erosion increase, they modify soil structure, which in turn reduces water infiltration and reservoirs recharge. The associated functions that a forest cover usually plays are also affected: thermal regulation, biodiversity support, and carbon sequestration, among others. Forest resources at the Biosphere Reserve of Monarch Butterfly have historically been under heavy pressure. Therefore, deforestation at this zone has been documented, along with ecosystem deterioration and depletion of wooden resources (PROFEPA, 2001). For such reason, the tool here presented attempts to economically calculate the losses on ecosystem services that DOI 10.1007/978-94-007-1858-6_11, © Capital Publishing Company 2012 164 e , J.K. Thakur et al. (eds.), G ospatial Techniques for Managing Environmental Resources