Elephant space use and impacts on vegetation in response to habitat expansion in succulent thicket

Elephant alter vegetation composition and structure, and at high densities biodiversity declines. While habitat expansion is one of several tools proposed to mitigate such effects, its effectiveness remains untested. Despite previous incremental expansions of the Addo Main Camp section of the Addo Elephant National Park to reduce the impacts of elephant on vulnerable Succulent Thicket habitats, significant declines in plant species richness, density and biomass were recorded. During 2010 the addition of the Colchester section effectively doubled the area (120 km2 to 230 km2) available to elephant, presumably releasing browsing intensity in the Addo Main Camp section, hence allowing for the regeneration (through growth and resprouting) of the vulnerable canopy shrubs (a key functional guild). I aim to test this hypothesis. I use space use data from before and after expansion to track the distribution of elephant utilization across the park. Additionally, I use data collected between 2008 and 2015 on shrub composition and structure and the structure of individual canopy species, to illustrate the long-term trends in elephant impact. I firstly show that although elephants shift a proportion of their utilization distribution into novel habitat, they continue to show a strong preference for the Addo Main Camp section, with its higher water availability yet heavier utilized vegetation. I also illustrate that within 5 years of the expansion, effects on the canopy shrub community declined, presumably by spreading impacts to novel areas. Specifically, I show that vegetation composition and structure (volume and density) remained stable during this period. While these results indicate that range expansion might be a viable tool to mitigate the impact of elephant on vegetation composition and structure, at least in the short-term, the consequences for ecological functioning remain to be measured. In the long-term, I predict that attempts to use range expansion as a management tool may fail if implemented without limiting population numbers and controlling the distribution of local densities (e.g. by managing surface water availability)