improved resource use, and ecosystem efficiency and productivity. For example, biodiverse grasslands outperform the best monocultures, producing better and storing more carbon (Tilman et al., 2002). In general, there is a positive correlation between species richness and productivity, and ecosystem resilience to drought (Tilman, 1997). In SSA, diversified farming reflects local knowledge and farmer innovations (Crucible II Group, 2000). AKST has built on traditional practices. For instance, live fences contribute to the ecological integrity of agricultural landscapes (Harvey et al., 2005) in the Sahel. Research in Uganda found species utility and occurrence is related to farmer socioeconomic status (Eilu et al., 2003). Concern for the loss of biodiversity and its impact on food security and productivity is an important driver of AKST. Wild biodiversity contributes significantly to the productivity and sustainability of agriculture, forestry and fisheries, and is addressed directly within some integrated natural resource management strategies (Lemons et al., 2003).

3.4.3.1 Agrobiodiversity
AKST has had a fundamental influence on agricultural biodiversity and has affected African production systems and development goals. SSA is the center of diversity for several of the world’s most important crops, including coffee, sorghum, lentil, wheat, barley, African rice, oil palm, yam
and cowpea (IAC, 2004). Over the years, large investments have been made in developing complementary genetic conservation combining in situ and ex situ technology (Damania, 1996). In situ conservation is vital because it provides a pathway for preserving complete biological diversity. It continues important basic necessities, such as medicines, fodder, food cosmetics, industrial products, fuelwood and timber, upon which most humankind depends. Wild species, including relatives of cultivated plants, are crucial in crop improvement programs as sources of genes for disease and pest resistance, environmental adaptability and nutritional qualities. In situ conservation evolved to establish and sustain
a broad genetic base, stabilize and maintain populations and present opportunities for expanding agricultural systems (Chang, 1994).

Species conserved in situ with different AKST approaches are likely to have uses as components in industry, medicine or breeding, for cultural uses and biocontrol programs. In situ conservation continues the cultivation and maintenance of landraces on farms, in the areas where they evolved and developed their distinctive properties. Such conservation may provide farmers with the incentive to act as custodians of traditional varieties nurtured in their fields and backyards (Altieri and Merrick, 1987). Crop diversity conserved in situ encourages traditional culture and agriculture. The domestication of trees and crops and their integration into agricultural landscapes has led to diversified production systems and increased agricultural productivity, while helping provide options and averting risks against crop failure.

3.4.3.2 Tree diversity
About 10,000 tree species are native to Africa, comprising about a fifth of the world’s tropical tree species. Few welldocumented germplasm collections of African tree species

exist. Exceptions include those for Acacia karroo, Allanblackia spp., Irvingia gabonensis, Prunus africana, Sesbania sesban, and Uapaca kirkiana. Few molecular genetic taxa have been investigated (Dawson and Powell, 1999). While substantial tree planting has taken place in some areas, it has been limited to a few taxa (Simons et al., 2000; Kindt et al., 2004). Concerns about overdependence on a few taxa have been borne out by pest problems on Cupressus lusitanica and Leucaena leucocephala. Farmers, however, can only plant what is available, and the tree germplasm available is inadequate.

The inadequacy of tree germplasm in SSA has been recognized for some time. The FAO Global Programme for Conservation and Management of Forest Genetic Resources set up in the 1960s and 1970s brought the attention of governments and donors to the situation in Africa. The approach taken was to provide support for breeding programs of industrial tree species, especially tropical pines and eucalypts (Barnes and Simons, 1994). Both international and national government tree seed centers were established to multiply and distribute improved germplasm to plantations. The 1980s and 1990s saw the interest in social and development forestry trigger the formation of other central national tree seed centers, often working with many multipurpose tree species. Subsequent monitoring, however, revealed that these centers only covered the formal market, which in several countries was estimated at less than 10% of the tree seed market (Lilles et al., 2001). This shortfall in achieving development objectives was apparently because tree seed centers had been established by national tropical forestry action plans, which had largely ignored emerging informal and on-farm activities.

3.4.3.3 Livestock
Various domesticated livestock species were introduced to Africa between 5000 BCE and 2300 BCE, mostly from western Asia and the Near East. Over the centuries, African farmers and herders selected animals for specific attributes. There are currently more than 50 types of cattle and several breeds of sheep and goats.

AKST ex situ innovations for conserving genetic resources are developing improved varieties and building upon the variability of on-farm varieties. The conservation of germplasm has ensured the long-term availability of this vital raw material. Technology for ex situ conservation includes gene banks as sources of diversity for crop improvement programs. Currently, a large number of crop varieties are held in gene banks throughout Africa, mainly through partnerships involving CGIAR centers and NARIs. Examples include in vitro gene banks for banana in Gitega, Burundi, and ex situ seed banks developed with the assistance of Bioversity International in Ethiopia, Kenya, Sudan and Zambia, plus other countries. Agricultural science and technology has been used to characterize and evaluate the conserved genetic resources of germplasm, using widely available descriptor lists developed by different CGIAR centers and NARS.

Farmers over the millennia have helped protect agrobiodiversity. However, germplasm in gene banks has, in many instances, been reintroduced into agricultural production