**3. Land use, cover, and natural water resources**

Overgrazing is the major cause of desertification in the dry lands [16]. Other factors that cause desertification include urbanization, climate change, overuse of ground water, deforestation, natural disasters, and tillage practices in agriculture that make soils more vulnerable to wind [16, 17].

#### **3.1 Contextualized land uses in Kenya**

A land-use map represents the physical and biological cover over the land surface, consisting of vegetation, bare soil, water, and artificial structures. Landuse and land-cover information is significant in understanding the socioeconomic and environmental implications linked to the utilization of the available natural resources in a region. In Kenya, land use is classified into agriculture, forest, bushland, grassland, plantation, built-up and urban area, barren land, woodland, plantation, swamp, and water bodies (**Figure 2**).

Agriculture is estimated to occupy 48% of the total land area, out of which 9.8% is considered arable land, 37.4% is covered by permanent pasture, and 0.9% by permanent crops such as tea and coffee plantations. Tree cover is estimated at 6% while other land uses, such as urban areas and bare land, occupy about 45.8% [19]. Urbanization and expansion of agricultural land have increased the rate of conversion and fragmentation of the natural forest ecosystems leading to deforestation and eventually land degradation. Land-use/land-cover change is considered the primary causal agent of climate change due to environmental changes that lead to increased greenhouse gas emissions. However, the effects of climate change, viz. increased temperature and variability in precipitation, prompt the change in land use as communities try to adapt to the changing climate [20]. Therefore, the development of effective land-use management plans is crucial to ensuring Kenya's goals toward environmental sustainability under future climate scenarios. There is a need to assess the vulnerability and adaptive capacity of local communities so as to prioritize the solutions that will enable communities to cope and adapt to climate change.

#### **3.2 Contextualized tree cover types in Kenya**

Kenya's forest areas constitute a wide range of vegetation, viz. trees, shrubs, and grass species. The Kenya Tree Cover Types map (**Figure 3**) gives a detailed visual representation of the categories of different tree cover types found in Kenya. The tree cover types are mainly classified as open canopy, closed canopy, multilayered trees, and mangrove trees. Open canopy refers to a collection of relatively tall trees that are spaced and allow easy penetration of sunlight to the ground surface. Closed canopy forest is a thicket of mature trees whose leaves and branches are densely spaced

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

#### **Figure 2.**

*Mapped land-use classification for Kenya based on Kenya's geospatial data provided by the World Resources Institute [18].*

#### **Figure 3.**

*Spatial distribution of different types of tree cover in Kenya produced from the Environmental Systems Research Institute Kenya GIS data [21].*

creating a crown that encloses the understory and the forest floor. The canopy types are also distinguished based on the percentage of crown cover, that is, the proportion of the ground covered by the vertical projection of the tree canopy. The multilayered trees generally refer to the dense tropical evergreen forests having the appearance of structured layers that differ in the amount of sunlight penetration, ground cover, and water availability. The mangrove trees, which occupy about 1% of the land area in Kenya, include thickets along the coastlines, tidal estuaries, and salt marshes of Kenya. *Rhizophora mucronata* Lam is the principal species in most sites dominated by mangroves along the Kenyan Coast [22].

The closed canopy and multilayered trees each cover about 2% of Kenya's total land area and are mainly restricted to areas below an altitude of 3000 meters. Tree species dominance within this area is according to the Agro-Ecological Zone (AEZ) [23]. Moist forests occurring at 2100–3300 m above sea level, with rainfall above 1500 mm, are dominated by a variety of broad-leaved species that include *Tabernaemontana stapfiana* (Britten), *Dombeya goetzenii* (K. Schum), *Dracaena afromontana* (Mildbr), *Hagenia abyssinica* (Bruce J. F. Gmel), *Nuxia congesta* (Fresen), *Croton macrostachyus* (Delile), and *Podocarpus latifolius* (Thunb. Mirb) [23]. The drier montane forests occurring at 1800–2900 m a.s.l. with an annual rainfall of 700–1350 mm are characterized by species such as *Juniperus procera* (Endl), *Olea europaea ssp. africana* (Mill. P. Green), *Podocarpus falcatus* (Mirb.), *Cassipourea malosana* (Baker. Alston), *Acokanthera schimperi* (A. DC. Schweinf), *Ekebergia capensis* (Sparrm.), *Olinia rochetiana* (A. Juss.), *Teclea nobilis* (Delile), *Croton megalocarpus* (Hutch), and *Calodendrum capense* (L. f. Thunb) [23].

The open canopy trees and shrubs, woodland, and grassland vegetation are estimated to cover 65% of the total land area and represent the dominant vegetation type in the Arid and Semi-Arid Lands of Kenya [24, 25], with the dominant tree species being *Acacia mellifera*, *Acacia senegal*, *Acacia reficiens*, *Acacia tortilis*, and *Commiphora* sp. [26]. Presently, climate change is a major driver of the rate of encroachment into forested areas and the destruction of grasslands in the country. Climate change has led to competition for arable land resources due to declining water resources coupled with droughts and scarcity of arable land.

Evidence of climate change in Kenya has been manifested in the increased frequency of droughts and floods, changes in rainfall intensity and distribution patterns, and increased minimum and maximum temperatures. Future climate projections estimate that most regions in Kenya will experience a 100-mm decrease in long-season (March–May) rainfall by 2025 [27]. Increased climatic variability poses a threat to the trees and associated vegetation cover with regions such as the ASALs being most vulnerable to the adverse impacts. The projected climatic impacts are likely to exacerbate the rate of land degradation and desertification in the country.

#### **3.3 Contextualized water resources in Kenya**

**Figure 4** shows the distribution of Kenya water resources. The country relies mainly on freshwater resources represented by lakes, rivers, swamps, and springs as well as dams, water pans, and groundwater. Kenya's annual freshwater resources endowment is estimated to be 20.2 BCM (billion cubic meters) or 548 m3 per capita per year [28]. These surface water resources are highly dependent on the country's forested areas and highland ecosystems that serve as water catchments. The watersheds depicted on the map include the Ewaso-Samburu, Mt. Kenya and Aberdares, Mau and Western, Amboseli and Chyulu, and the Coastal forest and Marine watersheds. The major lakes in the country include, inter alia, Lake Victoria, Lake Nakuru, Lake Naivasha, and Lake Elementaita. Some of the major rivers include the Tana River, Mara River, Athi-Galana-Sabaki River, Tsavo River, Ewaso Ng'iro River,

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

#### **Figure 4.**

*Map of natural water resources in Kenya based on Kenya GIS data provided by the Environmental Systems Research Institute Kenya GIS data [26].*

and Nzoia Rivers. The wetlands represented on the map are classified into fresh water marshes, saline/alkaline marshes, mangrove, lake shorelines, and saltpans [29]. Despite harboring some of the great water towers of East Africa, Kenya is among water-scarce countries, with its per capita renewable freshwater potential being 235 m3 per annum [30].

Coupled with extreme climatic events, such as droughts and floods, the water resources in the country continue to show a declining trend and threaten the availability of water for economic and domestic use. In the past, prolonged dry seasons have led to 37% decline in the water levels in dams and other reservoirs subsequently causing crop failure, loss of livestock, and limited access to freshwater [31]. Additionally, increased frequency of floods has led to the destruction of land resources due to soil erosion, disruption of water supply systems, and the contamination of freshwater resources. Overall, climate change, destruction of water catchment areas and deforestation continue to increase water scarcity in Kenya.

#### **4. Preventive and corrective initiatives**

#### **4.1 Background on combating desertification in Kenya**

Like many other nations around the world, Kenya is threatened by desertification, land degradation, and drought. In some of the dryland areas such as in the North and North-Eastern Kenya, the deserts have eaten the once-potential landscapes turning them into inhabitable landscapes that cannot support humans, livestock, and even wildlife [3]. The government of Kenya, recognizing the importance of the country's dry lands to the country's socioeconomic development and realizing that they are being degraded fast, has sought ways of restoring and rehabilitating dry forests and woodlands, among other ecosystems in these lands. These ecosystems are comprised of trees that are specially adapted to the harsh climatic and edaphic conditions, providing important ecosystem services for communities in an environment where other types of tropical tree species would not survive. These trees are threatened and call for restoration and rehabilitation initiatives by the government through support and participation in thematic forestry research and development activities. These activities include restoration and sustainable management of woody resources through biodiversity assessments, conservation, rehabilitation, afforestation, and reafforestation in order to enhance plant diversity.
