Abstract:
The South African grassland biome is one of the most threatened biomes in South Africa. Approximately
45% of the grassland biome area is transformed, degraded or severely invaded by alien plants and the
remaining natural areas are highly fragmented. In this fragmented landscape, the connectivity between habitat
patches is very important to maintain viable populations. In this study we aimed to quantify connectivity of the
grassland biome in Mpumalanga using graph theory in order to identify conservation priorities and to direct
conservation efforts. Graph theory-based connectivity indices have the ability to combine spatially explicit habitat
data with species specific dispersal data and can quantify structural and functional connectivity over large
landscapes.We used these indices to quantify the overall connectivity of the study area, to determine the influence
of abandoned croplands on overall connectivity, and to identify the habitat patches and vegetation types most in
need of maintaining overall connectivity.Natural areas were identified using 2008 land cover data for Mpumalanga.
Connectivity within the grassland biome of Mpumalanga was analysed for grassland species with dispersal distances
ranging from 50 to 1000 m. The grassland habitat patches were mostly well connected, with 99.6% of the total
habitat area connected in a single component at a threshold distance of 1000 m. The inclusion of abandoned
croplands resulted in a 33% increase in connectivity at a threshold distance of 500 m. The habitat patches most
important for maintaining overall connectivity were the large patches of continuous habitat in the upper and lower
centres of the study area and the most important vegetation types were theWakkerstroom Montane Grassland and
the EasternTemperate FreshwaterWetlands.These results can be used to inform management decisions and reserve
design to improve and maintain connectivity in this biome.
