A discussion of the impacts of grazing is provided in the preceding section and will not be considered further here, but grazing is without doubt one of the major forces effecting change in pastoral systems.
Livestock can and do compete with several species of wildlife for forage in eastern Africa, but this may vary according to rainfall. Wildlife appear to avoid heavily grazed areas completely in arid northern Kenya (De Leeuw et al., 2001), but mix more closely with livestock in semi -arid rangelands in southern Kenya (Waweru and Reid, unpub. data).
Wildlife probably avoid areas close to settlements because livestock remove most of the forage. Around Samburu pastoral settlements in northern Kenya, Grevy's zebra graze away from the settlements during the day, but move close to them during the night (Williams, 1998). Samburu build their settlements along riverine areas, within walking distance of streambeds where Samburu dig wells. After livestock are put into their corrals for the night, zebra come down to the streambeds to drink and leave by the next morning. They may also come close to the settlements at night for better predator protection as well.
In the group ranches around the Maasai Mara game reserve, wildlife avoid areas very close to settlements, but cluster at intermediate distances from settlements (Reid et al., 2001). Wildlife may cluster around settlements to have access to moderately grazed grasslands, where their access to energy and nutrients is very high. They may also graze close by for protection from predators. Current settlements tend to be built on areas that have been settled for a long time and contain numerous old settlement scars where nutrient enrichment in the soils below old livestock corrals can last for a century or more (Muchiru, Western and Reid, submitted).
Livestock grazing and less frequent rangeland burning can strongly affect the state of the vegetation in rangeland systems. Wildlife and livestock systems, when side-by-side, often are of two different vegetative states: wildlife systems remain grasslands if elephants and fire are present (e.g. Dublin, 1995), while neighbouring livestock systems are much more woody (Western, 1989). Traditional rangeland burning is an essential practice to maintain the grassland state critical to grazers, but may reduce the amount of carbon sequestered in these ecosystems.
Fragmentation can also occur when fence lines are built to prevent the spread of disease or to prevent wildlife from foraging in enclosed pastures. This fragmentation prevents both livestock and wildlife from reaching parts of the landscape; often the fenced parts contain key resources like swamps and riverine areas. Impacts on wildlife are not entirely known, but decreases in population sizes and viability can be expected. Eventually, fragmentation can completely exclude species from an area.
Recent evidence suggests that the impact of cultivation on vegetation, wildlife and soils in pastoral ecosystems is greater than that of livestock. Expansion of cultivation fragments rangeland landscapes when farmers convert rangeland into cropland (Hiernaux, 2000). Land degradation through crop cultivation has been documented (Niamir-Fuller, 1999), but the impacts of livestock use and crop cultivation (or any other land uses) has rarely been compared. The conversion of savannah to cultivation in parts of the Mara ecosystem of Kenya, along with poaching and drought, has caused more than a 60 percent loss in resident wildlife populations in the Mara ecosystem in the last 20 years (Ottichilo et al., 2000; Homewood et al., 2001; Serneels, Said and Lambin, 2001).
In non-cultivated areas, mixed livestock-wildlife systems may be more productive than either wildlife-only or livestock-only systems (Western, 1989). These mixed systems, when maintained at moderate livestock grazing levels, coupled with pastoral rangeland burning, may support higher levels of plant and animal biodiversity than livestock-only or wildlife-only systems, analogous to the increase in plant diversity seen at the edge of wildlife reserves frequented by pastoralists and their livestock (Western and Gichohi, 1993). Further, it is hypothesized that when livestock populations are moderate in size or mobile, pastoralism produces significant global benefits in the form of biodiversity conservation, carbon sequestration, soil retention, soil fertility maintenance and catchment protection.
Estimates of how the expansion of cultivation will affect pastoral systems over the next half century are based on scenarios of human population growth and climate change for the year 2050 from Reid et al. (2000a) and Thornton et al. (2002). Surprisingly, these changes may bring about an absolute expansion of cultivation of only 4 percent, or a relative increase of about 15 percent (Figures 2.8 and 2.9). Most of the change will probably occur around the edges of currently cultivated land in areas with the most rainfall. Thus pastoral areas are expected to continue to contract further in the future and pastoral peoples to either continue to adopt agropastoralism or become restricted to drier and drier land.
It is not clear whether current changes in the eastern Africa n rangelands (land use change, overgrazing, fragmentation) are causing a net release or net accumulation of carbon, either above or below ground. Expansion of cultivation into rangelands probably strongly reduces carbon below ground, but may increase carbon above ground if farmers plant significant numbers of trees (the success of which depends on rainfall). If overgrazing converts grassland to bushland, then above-ground carbon will increase, but below-ground effects are unknown. In addition, rangelands are a significant carbon sink (IPCC, 2000), but the potential of these areas for further sequestration is not clear.
Figure 2.8 - Estimated extent of cropland and urban areas in eastern Africa in 2000. From Thornton et al., 2002.
Figure 2.9 - Projected extent of cropland and urban areas in eastern Africa in 2050. From Thornton et al., 2002.
Although grazing effects can be difficult to disentangle from the effects of climate, those that have attempted to do so show that livestock grazing can drive grassland systems into bushland (Archer, Scimel and Holland, 1995). Heavy livestock grazing can convert grassland to bushland in eastern Africa, analogous to that observed in southern Africa (Ringrose et al., 1990). Sometimes this conversion forms a monospecific stand of persistent woody species, which greatly reduces biodiversity (de Queiroz, 1993).
Rehabilitation of grasslands usually involves use of exclosures and restricted access to allow the vegetation to recover and natural species to re-establish from the seed bank in the soil or from spread of plants by vegetative means. Grime (1979) recognized a variety of mechanisms of regeneration, with different types of revegetative strategies based on disturbance, vegetative cover and management, and proposed a model of vegetative succession and vegetation dynamics. Vegetative expansion is associated with undisturbed habitats with few seedlings and relies on rhizomes and stolons of perennial grasses. Seasonal regeneration of gaps involves synchronous germination of seeds from abundant seeders. Regeneration from persistent seed banks and wind dispersed seeds is associated with spatially unpredictable disturbances. Woody species also have persistent seed and seedling banks but opportunities for recruitment are infrequent. Disturbances alter ecosystem processes and may alter the equilibrium balance of the system (Chapin, 2003). Disturbances are usually revegetated by species of the original community and return to the previous species composition within a few years (Belsky, 1986). Introduction of new species through colonization and recruitment following disturbances may result in system change, and plant traits may be important indicators to predict the consequences of global change (Chapin, 2003).
Many previous attempts at rehabilitation have not been successful due to lack of consultation and involvement of local communities and their customs, and a perception that traditional systems need changes. Many technological interventions have been tested in the rangelands of southern Ethiopia but lack of development impact is linked to unrealistic expectations of development planners and poor appreciation of social values and production rationale of pastoralists (Coppock, 1994). Community participation in rehabilitation of degraded rangelands is an important step in promoting the success of current projects. A system in Samburu District in Kenya built on local knowledge and traditions to work in partnership with local people on local problems is having some success (Herlocker, 1999).
Rehabilitation offers an opportunity to sequester carbon through forestation, grass and shrub establishment. This is particularly important because pastoral lands are so extensive and they sequester large amounts of carbon. Rangelands are only second to tropical forests in the amount of carbon they sequester, although most of this sequestration is unseen below ground in rangelands, in contrast to carbon above ground in rain forests (IPCC, 2000). Poor use of rangelands can cause up to a 50 percent loss in soil carbon, so the potential gains from rehabilitation are substantial (Cole et al., 1989; IPCC, 2000; Reid et al., 2003).
Reseeding has been tried, with limited success, using thirty-two different species of grasses in Kenya (Bogdan and Pratt, 1967), although disturbance with subsequent colonization and regrowth was found to be successful for revegetation in the Serengeti Plains of Tanzania (Belsky, 1986). Options to improve success in Kenya were identified as selection of appropriate species for the ecosystem, good quality seeds, integration of reseeding with overall land management policy, adequate seedbed preparation, reasonable rain and a complete rest from grazing during the establishment period (Bogdan and Pratt, 1967). Chloris roxburghiana was difficult to establish in the south Kenya rangelands using seeds collected from natural stands (Mnene, Wandera and Lebbie, 2000). While there is the opportunity to introduce more productive exotic species into the system, these may often not be as well suited to the environment as the indigenous species and may not establish well. The study by Mnene indicated that ecotypes of the same species from different areas also showed poor establishment compared with seeds collected from populations in the same area.
Seed supply to support reseeding is a major constraint in eastern Africa and most species have to be collected from the wild (Bogdan and Pratt, 1967), a situation that has changed little over the past 30 years. Most succession in pastoral areas is through natural means, such as wind dispersal, although some projects are collecting seeds from natural stands for revegetation purposes. A limited number of cultivars of Rhodes grass, setaria, coloured guinea grass (Panicum coloratum) and signal grass (Urochloa decumbens) are available in Kenya from the Kenya Seed Company. These are useful for pasture establishment but have limited use for reseeding rangelands, except for revegetation of the Hyparrhenia tall-grass region as described by Herlocker (1999) and other areas where these grasses are an important part of the natural ecosystem. These species can also be used for range improvement due to their high palatability and nutritive value, but establishment is often poor due to low rainfall and competition, as well as open grazing during the establishment phase (Bogdan and Pratt, 1967).
In the late 1970s, the World Bank withdrew 98 percent of its funding to pastoral research and development because there had been little progress in improving the intensity of production in livestock-dominated systems (de Haan, 1999). The pressure to intensify existed despite the fact that crop cultivation of ten failed in these systems and often was unsustainable over the long term (Niamir-Fuller, 1999). Intensification of production has had such success in higher potential land that policy-makers assumed it was appropriate for pastoral lands, particularly because most policy-makers have received their training in cropping systems for wet areas, with no personal experience in extensive rangelands (Horowitz and Little, 1987). It might be that the intensification paradigm is inappropriate for pastoral lands and that the success and sustainability of production depends on extensification rather than intensification, maintaining mobility and flexibility for opportunistic production (e.g. Sandford, 1983; Scoones, 1995).
In addition, recent re-evaluations have recognized that livestock production is not the sole value of pastoral lands; rather, the focus might be more appropriately placed on improving pastoral livelihoods and maintaining ecosystem health in these vast lands (de Haan, 1999; Niamir-Fuller, 1999). A consensus is emerging that pastoral lifestyles are more compatible with maintenance of rangeland integrity than are other types of land use.
Pastoral systems in eastern Africa are rapidly evolving, driven by a combination of policy changes, drought, migration and human population pressure. Research and development efforts need to recognize such change and develop ways to understand and mitigate the effects of these changes.
Eventually, if major constraints are removed, it may be possible for pastoralists to herd more productive livestock breeds in eastern Africa n pastoral ecosystems. Until that happens, the focus should be less on production increases per se and more on diversifying livelihoods and maintaining environmental goods and services in pastoral lands (de Haan, 1999). There is good potential for alternative sources of income within pastoral areas from plant products (resins, medicinal plants), pastoral ecotourism and wildlife tourism (de Haan, 1999). There is some suggestion that income from ecotourism will surpass income from beef production in these lands in the developed world over the next decade (de Haan, 1999). Analogous to the Clean Development Mechanism of the Kyoto Protocol, it eventually may be possible to pay pastoralists (through biodiversity credits, for example) for maintaining ecosystem goods and services that have global benefits.
Recent reviews of pastoral development emphasize the probable failure of many technical interventions in pastoral ecosystems. Blench (2000) suggests that the best way forward is better provision of high quality information to pastoralists, by asking the question: What will pastoralists do if they have access to more and better information? Pastoralists, because of their mobility and loose connections to national economies, are likely to be some of the last to have access to information in any form, particularly high technology information.
In many parts of eastern Africa, pastoralism is the only way to convert sunlight into food. In these systems, new policies and management practices can still learn from the wisdom of Stephen Sanford (1983): opportunistic management of widely varying forage resources will be essential to reducing pastoral vulnerability. This means that maintenance of mobility and flexibility in grazing management strategies will remain particularly important. Another issue in eastern Africa is security - pastoral livelihood will hardly improve in areas where there is armed conflict. Asset and income diversification and improved access to information and external resources will also help. Improved risk management will enable pastoralists to take action to reduce the chance of losing assets, income or other aspects of well -being (Little et al., 2001).
We conclude this chapter with a number of questions that remain either unanswered or partly answered, but that must be addressed fully in eastern African rangelands. How many pastoralists are there in eastern Africa? How poor are pastoralists compared with people in crop-livestock systems? What is the evidence that eastern African rangelands are degraded (Niamir-Fuller, 1999)? Does the magnitude and variability of rainfall modify the effect of the driving forces of change in pastoral ecosystems? How does extensification of pastoral systems in eastern Africa affect ecosystem goods and services? What are the ecological and economic costs and benefits of different land use practices and land use change in these systems? How do pastoral land use practices (adoption of cultivation, abandonment of nomadism, permanent settlement, landscape fragmentation) affect the distribution, diversity and viability of nutrients, vegetation, biodiversity and landscapes in pastoral ecosystems in eastern Africa? How do changes in land tenure and economic policy affect pastoral ecosystem structure and function? How do changes in pastoral ecosystems affect household incomes and nutrition? What are the economic, social and ecological values of global ecosystem goods and services provided by pastoral ecosystems in eastern Africa (Homewood, 1993; Niamir-Fuller, 1999)? What are the most reliable and broadly comparative indicators of ecosystem change across eastern African pastoral systems (e.g. microbes, soil crusts)? What forces serve to enhance or maintain complexity in pastoral ecosystems and livelihoods, and what decreases complexity? How do we establish benchmarks for ecosystem and livelihood change in pastoral systems that are already heavily used?
Does the addition of livestock to wildlife -only systems in eastern Africa improve biodiversity and nutrient cycling? What social institutions best promote mobility and flexibility of land use among pastoralists and what policy alternatives can strengthen these institutions (de Haan, 1999)? What information is most useful to pastoralists and policy-makers, and in what form is it most easily accessible to each group? What types of incentive encourage extensification rather than intensification of pastoral ecosystems? How can pastoralists be compensated for protecting environmental goods and services of benefit to the globe? Will carbon credits work for pastoral lands? How can pastoralists take advantage of global conventions and funders (UN Convention to Combat Desertification (CCD); Global Environment Facility (GEF))? How can pastoralism be better integrated with crop cultivation in areas where such integration would be beneficial? How and when is co-conservation (integration of pastoral production and biodiversity conservation) most successful in eastern Africa?
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