Abstract: Tropical forests around the world face severe forest loss and fragmentation due to anthropogenic pressure, breaking apart once continuous forest into small non-continuous fragments isolated by human made landscapes. While biodiversity loss and altered ecosystem functions, such as carbon sequestration and water regulation, are attributed to forest loss, the effects of fragmentation independent from forest loss are still not clear due to a lack of regional level data that is often unavailable. Our ability to track fragmentation effects through space and time is is critical for direct management strategies, yet this requires difficult or logistically challenging fieldwork. The goal of this study is to provide an analytical approach including regional level data obtained from Landsat and MODIS satellites to 1) track changes in climate, forest cover, and fragmentation over a 20-year period at Los Tuxtlas Biosphere Reserve, Veracruz, Mexico, and 2) monitor shift in ecosystem functions such as productivity and drought regulation. Forest loss was determined by looking at the reduction in forest cover while fragmentation was characterized using fragment area, amount of edge habitat, shape complexity and isolation or distance from once continuous forest. We defined three areas of varying forest loss and fragmentation severity within the study region, spanning an elevational and temperature gradient with variable productivity and water regulation. As forest loss and fragmentation increased, productivity and water regulation tended to decrease. In addition, we assessed the direct and indirect effects of forest loss and fragmentation on ecosystem functioning and found that fragmentation related impacts on productivity and water regulation were explained by forest loss indirectly. Furthermore, as forest loss and fragmentation became more prominent over time, productivity and water regulation decreased especially in more vulnerable areas of the Biosphere. Results of this study highlight the need to integrate regional and landscape level analyses to better detect the spatial and temporal effects of forest loss and subsequent fragmentation on ecosystem functioning.
