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.

Land degradation is occurring in almost all terrestrial biomes and agro-ecologies, in both low and high income countries. However its impact is especially severe on the livelihoods of the poor who heavily depend on natural resources. Despite the severe impact of land degradation on the poor and the crucial role that land plays in human welfare and development, investments in sustainable land management (SLM) are low, especially in developing countries. This chapter summarizes the results from global and regional levels as well as 12 case study countries. The chapter also draws conclusions and implications for taking action against land degradation. Land degradation stretches to about 30 % of the total global land area and about three billion people reside in degraded lands. The annual global cost of land degradation due to land use/cover change (LUCC) and using land degrading management practices on static cropland and grazing land is about 300 billion USD. Sub-Saharan Africa (SSA) accounts for the largest share (22 %) of the total global cost of land degradation. Only about 46 % of the cost of land degradation due to LUCC-which accounts for 78 % of the US$300 billion lossis borne by land users and the remaining share (54 %) is borne by consumers of ecosystem services off the farm. This further illustrates that land degradation is a global problem even though its impact is much greater on poor land users. The cost of taking action against land degradation is much lower than the cost of inaction and the returns to taking action are high. On average, one US dollar investment into restoration of degraded land returns five US dollars. This provides a strong incentive for taking action against land degradation. This study shows that simul

Land degradation is an important problem in Ethiopia, with more than 85 % of the land degraded to various degrees. Recent estimates using satellite imagery show that land degradation hotspots over the last three decades cover about 23 % of the land area in the country. The assessment of nationally representative household survey shows that important drivers of sustainable land management in Ethiopia are biophysical, regional and socio-economic determinants. Specifically, access to agricultural extension services and markets and secure land tenure are important incentives to adoption of sustainable land management practices. Thus, policies and strategies relating to securing tenure rights, building the capacity of land users through access to extension services, and improving access to input, output and financial markets should be considered in order to incentivize sustainable land management. Important local level initiatives and institutions to manage grazing lands and forests through collective action should also be encouraged. We use the Total Economic Value approach (TEV) to estimate the cost of land degradation in Ethiopia. The annual cost of land degradation associated with land use and cover change in Ethiopia is estimated to be about $4.3 billion. Only about 51 % of this cost of land degradation represents the provisioning ecosystem services. The remaining 49 % represent the loss of supporting and regulatory and cultural ecosystem services. Use of land degrading practices in maize and wheat farms resulted in losses amounting to $162 million-representing 2 % equivalent of the GDP in 2007. The costs of action to rehabilitate lands degraded during the 2001-2009 period through land use and cover change were found to equal about $54 billion over a 30-year horizon, whereas if nothing is done, the resulting losses may equal almost $228 billion during the same period. Thus, the costs of action against land degradation are lower than the costs of inaction by about 4.4 times over

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Land degradation-defined by the Millennium Ecosystem Assessment report as the long-term loss of ecosystems services-is a global problem, negatively affecting the livelihoods and food security of billions of people. Intensifying efforts, mobilizing more investments and strengthening the policy commitment for addressing land degradation at the global level needs to be supported by a careful evaluation of the costs and benefits of action versus costs of inaction against land degradation. Consistent with the definition of land degradation, we adopt the Total Economic Value (TEV) approach to determine the costs of land degradation and use remote sensing data and global statistical databases in our analysis. The results show that the annual costs of land degradation due to land use and land cover change (LUCC) are about US$231 billion per year or about 0.41 % of the global GDP of US$56.49 trillion in 2007. Contrary to past global land degradation assessment studies, land degradation is severe in both tropical and temperate countries. However, the losses from LUCC are especially high in Sub-Saharan Africa, which accounts for 26 % of the total global costs of land degradation due to LUCC. However, the local tangible losses (mainly provisioning services) account only for 46 % of the total cost of land degradation and the rest of the cost is due to the losses of ecosystem services (ES) accruable largely to beneficiaries other than the local land users. These external ES losses include carbon sequestration, biodiversity, genetic information and cultural services. This implies that the global community bears the largest cost of land degradation, which suggests that efforts to address land degradation should be done bearing in mind that the global community, as a whole, incurs larger losses than the local communities experiencing land degradation. The cost of soil fertility mining due to using land degrading management practices on maize, rice and wheat is estimated to be about US$15 billion per year or 0.07 % of the global GDP. Though these results are based on a crop simulation approach that underestimates the impact of land degradation and covers only three crops, they reveal the high cost of land degradation for the production of the major food crops of the world. Our simulations also show that returns to investment in action against land degradation are twice larger than the cost of inaction in the first six years alone. Moreover, when one takes a 30-year planning horizon, the returns are five dollars per each dollar invested in action against land degradation. The opportunity cost accounts for the largest share of the cost of action against land degradation. This explains why land users, often basing their decisions in very short-time horizons, could degrade their lands even when they are aware of bigger longer-term losses that are incurred in the process.

Kenya is an agricultural nation, with over 12 million people residing in areas with degraded lands. Unfortunately, the food crop productivity growth in the country has failed to exceed the population growth. The growth of agricultural output in Kenya is constrained by many challenges including soil erosion, low productivity, agro-biodiversity loss, and soil nutrient depletion. Land exploitation devoid of proper compensating investments in soil and water conservation will lead to severe land degradation. This will translate to loss of rural livelihoods, diminished water supplies and threaten the wildlife habitat. This study explores the causes, extent and impacts of land degradation in Kenya, discusses the costs of action versus inaction in rehabilitating degraded lands, and proposes policy options for promoting sustainable land management (SLM). In order to appropriately support SLM, there is a need to account for the total economic value (TEV) of land degradation, i.e. including the value of both provisioning and indirect ecosystem services of land. Using such a TEV approach, findings show that the costs of land degradation due to land use and land cover changes (LUCC) in Kenya reach the equivalent of 1.3 billion USD annually between 2001 and 2009. Moreover, the costs of rangeland degradation calculated through losses in milk and meat production, as well as in livestock live weight decreases reach about 80 million USD annually. Furthermore, the costs of "soil nutrient mining" leading to lower yields for three crops, namely wheat, maize and rice in Kenya were estimated at about 270 million USD annually. The cost of taking action to rehabilitate lands degraded through LUCC is found to be lower than the cost of inaction by 4 times over a 30 year period, i.e. each dollar invested in land rehabilitation is likely to yield four dollars of returns. This may strongly justify the urgent need for taking action against land degradation. Addressing land degradation involves investments in SLM. Our econometric results show that improving access to information on SLM and to the markets (input, output, financial) may likely stimulate investments into SLM by agricultural households.

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