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Toward an integrated global assessment
Attention to land degradation and environmental pollution has increased significantly in the past 25 years, largely due to greater levels of international cooperation and recognition that local changes in land resources have global impacts. As the world’s focus on climate change increases, so, too, does the attention being paid to drought and its rise in frequency and severity. Despite this heightened global awareness, action to prevent or mitigate land degradation and drought at national or international levels has been limited, primarily because there are limited assessments regarding the cost of land degradation. Past global assessments have largely focused on the biophysical impacts of land degradation while little has been done to assess its global economic costs or the costs-versus-benefits of preventing or mitigating it. Additionally, past studies have largely focused on loss of on-site productivity and have paid limited attention to the off-site costs of land degradation and off-site benefits of land improvement. As part of the effort to address these and other gaps, this study was undertaken to prepare a framework for global assessment of the economics of desertification, land degradation, and drought (E-DLDD).
A review of literature on global evaluations of land degradation shows a significant development in methods and approaches to mitigate it. Earlier evaluations based their assessments on expert opinion and concentrated on only a few types of land degradation—namely soil erosion and deforestation. Recent studies have expanded the types of land degradation assessed to include other major indicators of terrestrial ecosystem services—made possible, in part, by rapid technological development. Specifically, satellite imagery has been used to assess vegetation land cover using normalized difference vegetation index (NDVI), which is a measure of plant growth vigor, vegetation cover, and biomass. The time series NDVI data are appealing because they are readily available, however, there has been criticism on use of NDVI as an indicator of land degradation or improvement.