Remote sensing provides a progressive record of vegetation change in northern KwaZulu-Natal, South Africa, from 1944 to 2005

Abstract

Remote sensing, together with geographic information systems (GISs), provide a powerful tool for monitoring environmental processes. Aerial and satellite photographs enable the analysis of an entire landscape and, using multi-temporal sets of photographs, one is able to follow processes over time. In our study, we used multi-temporal sets of aerial photographs, taken between 1944 and 2005, to observe the phenomenon of woody plant encroachment in four neighbouring study sites in northern KwaZulu-Natal, South Africa. We also analysed rainfall and temperature trends. Woody plant encroachment was evident in all sites. We suggest possible drivers behind the bush encroachment; in particular, climatic trends. However, encroachment did not relate directly to rainfall and temperature trends. We also speculate on the effects of herbivory and fire, as well as rising atmospheric CO₂ concentrations and its effect on C₃ and C₄ plants. We suggest that increasing atmospheric CO₂ concentrations could be the overriding driver of woody plant encroachment in our study area, with other drivers, such as rainfall, temperature, fire, herbivory, and land use, playing a modifying role.

Acknowledgements

We wish to thank the Chief Directorate of National Geo-spatial Information, Mowbray, for providing the aerial photographs; SA Weather, Agricultural Research Council, and the Talana Museum for rainfall and temperature data; Brice Gijsbertsen of the Geography Department (UKZN) and Clement Adjorlolo of Natural Resources (Cedara) for assistance with analysis of the aerial photographs; and the Rattray family at Fugitives’ Drift Lodge for accommodation during field trips.

Funding

We also thank the National Research Foundation for funding DW, the Gay Langmuir Bursary Fund for funding JR, and the South African Environmental Observation Network for technical and financial assistance.