Remote sensing and change detection in rangelands

Abstract

During the 20^th century, we have witnessed an improvement in the quality of imagery available for rangeland auditing, from the earliest mono-chromatic aerial photographs, followed by the first infra-red images, to the abundance of high resolution, multi-spectral imagery currently available. Of overwhelming concern is the difficulty of translating this information into a useful tool for making decisions about land management and intervention strategies. At one level, the land manager is always playing catch-up, as the technology for viewing and analysing imagery improves and out-strips his capacity. He is close to the land, making daily decisions about production and condition, but the images are snapshots taken two to three months earlier. To most land managers, remote sensing has remained illusive, seldom allowing the manager to use it to its full potential. In contrast, the policy maker, backed by GIS laboratories and remote sensing specialists, is confronted by plausible scenarios of degradation and transformation. After intervening, he is seldom active long enough to witness changes in the remotely derived land condition indices and fails to adapt decisions. Bridging this divide remains a challenge to the remote-sensing community and some possible mechanisms are suggested.



The major limiting factor for the wider utilisation of satellite imagery in rangeland assessment remains the cost of the imagery. Unless first world data suppliers show their commitment to sustainable development in real terms, data costs will remain a limiting factor.



Keywords: degradation, desired state, landscape function, production, transformation



African Journal of Range & Forage Science 2004, 21(2): 123–128