Desertification

Principal Investigator:

Stephen D. Prince

Non-degraded grazing land, at near potential productivity (NPP set by the climate and soil.)

Dryland degradation or desertification is widely believed to be a major global environmental threat, to which the international community has responded with the United Nations Conference on Desertification (UNCOD) and a Convention to Combat Desertification. Yet no objective definition or operational measurement techniques have been agreed for global application. Existing field and regional reports are subjective, qualitative and inconsistent, inhibiting regional and global assessment. In this project this problem is addressed at local to regional and global scales

Earlier work on this topic was undertaken in the Sahel (the southern fringe of the Sahara stretching from the Atlantic to the Red Sea). The region was the cradle of the desertification debate and it suffered several devastating droughts and famines between the late 1960s and early 1990s.

Desertified (degraded) grazing land in northern South Africa. Note sparse vegetation and soil erosion

We have demonstrated that reductions of potential primary production in drylands is a reliable indicator of the "diminution or destruction of the biological productivity of the land" - the UN Conference on Environment and Development definition of desertification (UNCED, Brazil 1992). The earth observation satellite record of the past 25 years is being used to estimate net primary production, thus providing an objective measurement of desertification. The results are the first objective map of current degradation in the world's drylands.

Recent work has been undertaken in known areas of desertification in southern Africa, including Zimbabwe and northern South Africa.The techniques have also been applied at the global scale. An important application of the new global inventory is to study the impact of degradation on the function of the Earth as a whole and also on the well-being of the vast population that lives in the semi-arid parts of the world.

Example publications: Prince S.D. and Wessels K.J. 2005. Satellite remote sensing and desertification. In: Millennium Ecosystem Assessment.
Wessels K.J., Prince S.D., Malherebe J. and others (submitted) Land degradation monitoring using remotely sensed estimates of vegetation production: controlling for inter-annual variation of rainfall in South Africa. Global Chance Biology.
Prince, S. D. 2002. Spatial and temporal scales of measurement of desertification. In Global desertification: do humans create deserts? M. Stafford-Smith and J. F. Reynolds. Berlin, Dahlem University Press. Pp 23-40.
Wessels, K., Prince, S.D., Frost, P., and van Zyl, D. 2004. Assessing the effects of human-induced land degradation in the former homelands of northern South Africa with a 1km AVHRR NDVI time-series. Remote Sensing of Environment. Volume 91(1), 47-67.