Biomass Productivity-Based Mapping of Global Land Degradation Hotspots

Abstract

Land degradation affects negatively the livelihoods and food security of global population. There have been recurring efforts by the international community to identify the global extent and severity of land degradation. Using the long-term trend of biomass productivity as a proxy of land degradation at global scale, we identify the degradation hotspots in the world across major land cover types. We correct factors confounding the relationship between the remotely sensed vegetation index and land-based biomass productivity, including the effects of inter-annual rainfall variation, atmospheric fertilization and intensive use of chemical fertilizers. Our findings show that land degradation hotpots cover about 29 % of global land area and are happening in all agro-ecologies and land cover types. This figure does not include all areas of degraded lands, it refers to areas where land degradation is most acute and requires priority actions in both in-depth research and management measures to combat land degradation. About 3.2 billion people reside in these degrading areas. However, the number of people affected by land degradation is likely to be higher as more people depend on the continuous flow of ecosystem goods and services from these affected areas. Land improvement has occurred in about 2.7 % of global land area during the last three decades, suggesting that with appropriate actions land degradation trend could be reversed. We also identify concrete aspects in which these results should be interpreted with cautions, the limitations of this work and the key areas for future research.

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“…Degraded elements include eroded, scalded, salinised or waterlogged soils, and overgrazed vegetation. It is estimated that land degradation hotspots cover around 29% of the global land surface area, with grasslands most severely affected (Le et al 2014). Of primary concern in this paper are managed, multi-value landscape elements, in which agricultural production and environmental conservation are both important goals.…”

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“…Secondly, the protection and sustainable use of natural resources by small farms is becoming a critical aspect of their productivity. For example, land degradation is found to affect more than three billion people around the world, the majority of whom are small farmers and pastoralists in developing countries (Le et al 2014), and has serious economic consequences for them (Nkonya et al 2011). Thirdly, globalization and changes in markets offer new opportunities and competitive threats for small farms.…”

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“…Secondly, the protection of natural resources and their sustainable use by small farms is becoming a critical aspect of farm productivity. For example, land degradation is found to affect more than 3 billion people around the world, the majority of whom small farmers and pastoralists in developing countries (Le et al 2014), and has serious economic consequences for them (Nkonya et al 2011). Thirdly, globalization and changes in markets offer new opportunities and competitive threats for small farms.…”

“…Sources: Lowder et al (2014), FAO; Le et al (2014) At the micro-level, Ali and Deininger (2015) also find that soil fertility is higher in smaller plots in Rwanda. It may be that farmers cultivate more fertile lands first, and move to less fertile lands while expanding their operations, or smaller farmers take better care of their land.…”