Land degradation remains controversial because of the lack of scientifically objective and consistent methods for monitoring and assessing the problem. The lack of reliable data poses a fundamental bottleneck to sound development policy and for assessing progress towards goals throughout the developing world. Land health surveillance borrows many scientific concepts andprinciples from the public health sector, where surveillance systems are well established and provide the main source of information for formulation and evaluation of public policy and practice. Many aspects of land degradation share similarities with chronic human disease problems, in terms of being persistent problems that are difficult and expensive to treat, and which emerge slowly in response to a complex web of proximal and distal drivers or risk factors. The intention has been to bring across much of the scientific rigour used in public health surveillance and apply it to land health. A second key feature of this work has been to draw on latest developments in geoinformatics to build operational surveillance systems for systematic collection of data on land health and associated risk factors that can be applied in landscapes everywhere and replicated to national and regionalscales. While the emphasis of land health surveillance is to provide scientifically objective information on land health, the approaches and methods can complement and enhance efforts to develop local indicators that can be used by local communities to monitor land health.
Part 1 of this publication presents scientific concepts of land health surveillance and the methods and analytical approaches that are used to make surveillance operational. Part 2 presents a regional application of land health surveillance with a synoptic screening study of land degradation in the Sahel using historical changes in vegetation growth and rainfall patterns, based on remote sensing. Part 3, describes a sampling and measurement framework for field level assessment of land degradation based on a sentinel site surveillance scheme and illustrates its application in Segou Region in Mali. Part 4, draws out the implications of the methods and results for development policy and research and identifies priorities for further development and application of the land health surveillance framework. The final chapter provides succinct recommendations for policy action. The main findings of this report are illustrated in a separate summary for decision makers and further illustrated in Sahel Atlas of Changing Landscapes: Tracing trends and variations in vegetation cover and soil condition. Land degradation poses a very real threat to sustainable development in the West Africa Sahel.
This study has revealed an incipient trend of land degradation across the region and a crisis in Segou Region in terms of the critically poor and degraded state of soil health in the areas most suited for agricultural production.