Long-term ecological changes at the edge of the Mara-Serengeti ecosystem
Protected areas in sub-Saharan Africa are fast becoming islands on which to conserve biodiversity as nearby human populations grow exponentially, rangelands become urbanized, and natural habitats are fragmented. The Mara-Serengeti ecosystem is renowned for having some of the highest densities of large mammals in the world. However, human population growth outside the boundaries of this ecosystem may be affecting important ecological processes inside reserve boundaries. Elucidating the impacts of expanding human populations around protected areas is critical for regional and global conservation efforts. Here we documented ecological changes occurring between 1988 and 2013 in the Talek region of Kenya, which lies inside the Masai Mara National Reserve along its northern boundary. For 25 years, we continuously monitored temperature, rainfall, numbers of resident and migratory herbivores, and the size of the local population of spotted hyenas. We documented long-term changes in these ecological variables, and modeled trends in these data in relation to changing anthropogenic activity along the edge of the Reserve, including size of the local human population, a burgeoning tourism industry, and livestock grazing.
All resident and migratory species of mammalian herbivores monitored here declined significantly between 1988 and 2013. In contrast, the local spotted hyena population has undergone rapid and surprising growth during the last 8 years of this study. The ecotourism industry continues to grow unchecked in this region of the Masai Mara National Reserve, and local pastoralist populations continue to grow exponentially along the northern border of the Reserve. However, above all, our results indicate that the habitual, illegal grazing of livestock within Reserve boundaries is having sweeping direct and indirect effects on herbivore and carnivore populations. Whereas moderate levels of grazing by livestock may affect local wildlife positively, the habitual intensive grazing taking place in the Talek region now appears to be having profound and widespread negative impacts. Our results suggest that, if management and conservation efforts do not change drastically and soon in this region, it is likely that local wildlife diversity will continue to decline.