**2. Desertification process and Kenya's context**

Drylands occupy 41% of the earth's land surface and are home to 35% of its population. They occur in every continent but are most extensive in Africa. The drylands include desert, grassland, and savanna woodland biomes. In Kenya, the drylands make up 84% of its total land surface, support about 9.9 million Kenyans (about 34% of the country's population), and account for more than 80% of the country's ecotourism interests, 60% of the nation's livestock, and up to 75% of the national wildlife population [5, 6]. Although rich in natural resources, the increased human pressure on forests and woodlands has created conditions conducive to degradation, deforestation, and desertification. The drylands environment poses formidable problems for sustainable development. Among these are unpredictable and severe drought, desiccation or aridification due to persistent drought, and dryland degradation or desertification [7]. However, drylands in Kenya are vast and offer a great potential for intensified afforestation toward achieving the national objective of 10% tree cover.

Desertification is defined as land degradation in arid, semiarid, and dry subhumid areas resulting from many factors, including climatic variations and human activities. These areas are characterized by low and erratic rainfall, high evapotranspiration, shallow soils with low water-holding capacity, and low soil fertility [8]. Drought is a common occurrence in the Arid and Semi-Arid Lands (ASALs) and is exacerbated by climate change [9]. It is caused by rainfall deficit; it leads to shortage of water and unusually high temperatures. Anthropogenic causes of desertification include overgrazing, deforestation, and removal of the natural vegetation cover by taking too much fuelwood, the build-up of salt in irrigated soils, topsoil erosion, and agricultural activities in the vulnerable ecosystems of arid and semiarid areas that are thus strained beyond their capacity. These activities are triggered by population growth, the impact of the market economy, and poverty. The phenomenon reduces agricultural output, contributes to droughts, and increases human vulnerability to climate change.

The differences and interlinkages between desertification, drought, desiccation, and climate change and their causal factors have been outlined in many texts [7]. Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become increasingly arid [10]. Land degradation is a process in which the value of the biophysical environment is affected by a combination of human-induced processes acting upon the land [11]. It is viewed as any change or disturbance to the land perceived to be deleterious or undesirable. Permanent changes in climate, particularly rainfall, are responsible for natural desertification. Desertification may alter the living conditions of the local flora and fauna that makes it impossible for animals and plants to sustain their populations. After desertification, regions suffer from water shortages due to climate change and animals may suffer and die since water is vital for all life on the planet. Desertification results in persistent degradation of dryland and fragile ecosystems due to man-made activities and variations in climate. Desertification, in short, is when land that was of another type of biome turns into a desert biome because of changes of all sorts.

*Combating Desertification through Enhancement of Woody Floral Diversity in the Drylands… DOI: http://dx.doi.org/10.5772/intechopen.100399*

Desertification affects topsoil, groundwater reserves, surface runoff, human, animal, and plant populations. A study conducted in the Mutomo District, Kenya, confirmed that the main use of selectively harvested trees was charcoal production [12]. This consequently led to degradation of the woodlands through reduction in tree species richness, diversity, and density. Water scarcity in drylands limits the production of wood, crops, forage, and other services that ecosystems provide to our local communities. The United Nations Convention to Combat Desertification states on its website that, globally, more than 12 million hectares of land are lost annually to desertification, drought, and degradation and that over 1.5 billion people are directly dependent on land that is being degraded, leading to loss of US dollars-equivalent billions of earnings each year [13]. In Africa, three million hectares of forest along with an estimated 3% of Gross Domestic Product (GDP) are lost annually due to depleted soils. The result is that two-thirds of Africa's forests, farmlands, and pastures are now degraded.

The dry lands on average receive an annual rainfall of between 250 and 1000 mm. **Figure 1** shows the extent and levels of aridity in Kenya. The rains are typically of short duration but of high intensity and therefore highly erosive. The rate of evapotranspiration is also high. The aridity values on the map legend are based on the generalized climate classification scheme for Aridity Index values [15] as follows (**Table 1**). No region in Kenya is classified as Hyperarid (Aridity Index Value <0.03).

The main challenge in developing dry lands is how to increase availability and access to information and technology for the development and management of natural resources.

#### **Figure 1.**

*Kenya aridity index map produced based on the Global Aridity Index and Potential Evapotranspiration (ET0) Climate Database v2 [14].*


**Table 1.**

*Aridity context in Kenya.*
