Fencing protected areas: A long-term assessment of the effects of reserve establishment and fencing on African mammalian diversity

Conservation of biodiversity is one of the great challenges faced by present societies. Establishment and fencing of protected areas to isolate biodiversity from human activities is one of the most popular methods for achieving this protection. Here we analyze two long-term (∼50 years) datasets on a diverse mammal community of 38 regularly occurring species including many of international conservation importance such as the rare, endemic mountain bongo (Tragelaphus eurycerus isaaci), the black rhino (Diceros bicornis), the elephant (Loxodonta africana), and the lion (Panthera leo). These data were collected in two different locations within a flagship protected area in East Africa. Our primary objective was to investigate patterns of wildlife populations and diversity before and after the installation of a perimeter electric fence. We find strong evidence for long-term human-induced edge effects at the site that is closest to the border of the protected area (Treetops); this site registered the strongest losses in total wildlife population numbers, aggregate wildlife biomass, and species richness. In contrast, wildlife populations at the site farther away from the edge of the protected area (The Ark) have remained relatively stable over the duration of the dataset. Our data reveal clear differentiation in the temporal changes of wildlife populations between the two sites. Establishment of the fence in 1989 led to temporary increases in wildlife populations near the park margins, but since the late 1990s these gains have been reversed and wildlife populations have continued to decline near the edge of the reserve. Without the intention of undermining the potential value of fences as conservation tools, our data suggest that fences are only as effective as the management and enforcement efforts that accompany them.