Vegetation change in northern KwaZulu-Natal since the Anglo-Zulu War of 1879: local or global drivers?

摘要

The quality of the landscape is declining in many grassland and savanna areas of Africa as a consequence of woody plant encroachment. We investigated the changes in vegetation at selected sites on the battlefields of the Anglo-Zulu War of 1879 in KwaZulu-Natal. We used fixed-point repeat photographs to compare the landscape at the time of the Anglo-Zulu War with the same landscape in 2011. Nine photo-pairs were analysed, covering three specific sites: Isandlwana, Fugitives' Drift and Rorke's Drift. A further eight photographs from these sites, taken during the intervening years, were matched and compared with the present landscape. All sites we analysed showed an increase in woody cover since 1879. We used the Whittaker plant diversity sampling method to determine current woody and grass species composition on the sites. We also investigated the effect of catena, aspect, rockiness and land use on the bush encroachment. Rainfall and temperature data were also analysed. The observed large increases in woody cover cannot be explained by land use or by local climatic conditions only. The changes are also consistent with global climate change effects, most likely due to increasing atmospheric CO2.