Fifteen-year resilience against further degradation of Succulent Karoo vegetation in South Africa

Abstract

The Tankwa Karoo National Park (TKNP) is part of a renowned arid biome with unrivaled diversity in succulents. The park has been subject to anthropogenic pressures such as heavy grazing with climate change a recent threat. This study investigated changes in vegetation productivity between 2000 and 2014 across six vegetation types using rainfall and satellite data. The park is broadly divided into a plain at low altitude (316 m) receiving less rain and a wetter, higher terrain (1640 m). Long-term rainfall varied from 265 mm y-1 in the highland areas to 100 mm y-1 in the plains. There was a significant corresponding rise in NDVI from the low to the highlands (p < 0.001). Our analyses suggest that vegetation has stabilised since the park was proclaimed in 1984 because 81% of the area has remained uniform, on average, despite considerable variation on a vegetation type basis. Only 18% of the park had increasing productivity while just 2% experienced a decline. The patterns also suggest vegetation was principally controlled by rainfall, rather than a shift in land-use from rangeland to conservation. This implies that much of the presumably endemic degradation in the Succulent Karoo Biome is not evident in the Tankwa.