**1. Introduction**

Desertification is at the forefront of the environmental crises currently facing the international community. In sensitive and fragile desert-adapted ecosystems, degradation processes can easily be converted into an irreversible trend. Desertification reduces access to ecosystem services, increases food insecurity and poverty, and affects communities' well-being [1]. Desertification is land degradation or the impoverishment of arid, semi-arid (drylands), and some subhumid ecosystems, resulting from many factors including human activities and climatic change. The assessment of global scale desertification vulnerability to climate change and human activity is important to help decision-makers formulate the best strategies for land rehabilitation and combat global desertification in sensitive areas [2]. The range and intensity of desertification have increased in some dryland areas over the past several decades [3].

Drought and unreliable and variable rains are recurrent problems. Even without climate change, drylands face a daunting array of threats including population pressure, social changes (e.g. settlement of traditionally nomadic peoples), and exploitive agricultural and grazing practices that increase deforestation, soil erosion,

salinization, and water depletion. Many political and institutional problems have conspired to degrade 20% of the world's drylands, including 22% of Asia's and 25% of Africa's susceptible drylands [4].

Regions like Africa are particularly vulnerable to desertification since two-thirds of the continent is made up of either deserts or drylands, while 73% of its agricultural drylands are already degraded. More than two-thirds of its population is composed of subsistence farmers, and, therefore, the impact of land degradation is immediate and devastating [5].
