*4.3.5 Biodiversity conservation in Kenya*

Although Kenya's biodiversity remains highly protected, declines are common phenomena due to a number of anthropogenic threats that have led to numerous conservation challenges [57]. Nevertheless, the country explores all avenues to ensure that efforts to win the war against biodiversity losses are sustained. Examples of progress made in research and development for drylands afforestation in Kenya include the following:

#### *4.3.5.1 Selection of appropriate tree species*

Until the 1980s–90s, when it became a government policy in Kenya to promote the replanting of indigenous rather than exotic tree species, most of the work on the selection of trees of arid and semiarid lands in Kenya was with exotic fastgrowing species [53]. Since then, selection criteria have continued to evolve with consideration around preferences of local communities, availability of quality genetic material for propagation, and site biophysical conditions. Currently, a large number of tree species have been recommended for the drylands of Kenya [52, 53]. In the dryland areas of Kitui and Kibwezi (Eastern Kenya), tree species grown and recommended include *Azadirachta indica*, *Jatropha curcas*, *Senna siamea*, *Leucaena leucocephala*, *Croton megalocarpus*, *Casuarina equisetifolia*, *Melia volkensii*, *Eucalyptus camaldulensis*, and *Dovyalis caffra* [4].

In Kenya, the area under *Eucalyptus* is likely to increase as a result of high demand for transmission poles, for construction, fuelwood, carbon sequestration, and mitigation of the effects of climate change [58]. However, there is much unease about Eucalyptus water consumption as compared to other woody flora. On a positive note, studies have established that Eucalypts exhibit high efficiency in water use for biomass accumulation. It has been established that eucalyptus requires less water to produce one (1) kg of biomass than most crops [59].

*Melia volkensii*, an important timber species that grows well in well-drained soils, is a promising indigenous tree species found in the drylands of Kenya. It is fast growing, drought tolerant, and produces high-quality hardwood timber for furniture. However, this species is heavily exploited in its natural stands and the trend has been worsening over the last decade owing to shortage of alternative hardwood species in drylands. As a result, programs promoting domestication of the species as a plantation species are ongoing [60–62].

#### *4.3.5.2 Development of suitable methods for propagation*

Poor propagation of some promising tree species in the drylands of Kenya has slowed down the country's efforts to increase its forest cover to the targeted 10%. For example, lack of seedlings attributed to poor seed germination is experienced with *Terminalia brownii*, a drought-tolerant species, which can be used to rehabilitate degraded drylands through reforestation and agroforestry approaches [63]. The current demand for Terminalia seedlings is higher than the supply. Research has focused on development of technologies ranging from breakage of dormancy to plant-tissue cultures to improve germination propagation of such species. Studies have been conducted to investigate the dormancy and germination of *T. brownii* seeds collected from various dryland sites in Kitui, Makueni, Tharaka-Nithi, and Baringo Counties of Kenya. Extracted seeds recorded the highest germination with the best at 76% compared to nipped seeds (13%) and those subjected to other treatments [63]. *Melia volkensii* Gurke is another drought-tolerant tree native to the drylands, of which cultivation is limited by difficulties in propagation via conventional means. Full exploitation of the ability of thidiazuron to elicit regeneration in plant-tissue cultures, as a sole plant growth regulator, was found to be hampered by high costs. Alternative effective and low-cost agrochemical thidiazuron for in vitro propagation of *M. volkensii* was found to be Kingtai-TDZ, which has a high potency and suitability for use in tissue culture of the species [61]. Because of difficulties in seed germination, land users sometimes go for the use of plants produced from root and stem cuttings, rather than from seedlings, and researchers have focused on the possibility that root and stem cuttings may be used for propagation, rather than seedlings [62]. However, if cuttings

are used to circumvent the problems of seed germination, alternative methods of controlling competition, such as root pruning, need to be considered.
