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In order to tackle poverty and hunger in sub-Saharan Africa (SSA) there is a strong case for a focus of effort on improving rainfed agricultural systems. The challenge is to deliver a transformation of agricultural productivity in such systems without adverse impacts on environmental goods and services. We examine the growing advocacy of 'conservation agriculture' (CA) as the desired approach and assess the evidence to support the assertion that it can deliver sustainable agricultural development in SSA. We examine in particular the evidence which derives from experience with 'zero tillage sustainable agriculture' in Brazil. We ask the question, is there a case for a paradigm shift in land husbandry? The case for a paradigm shift hangs on the premise that conventional practice promotes land degradation, while adoption of CA practice delivers a range of benefits through promoting soil ecosystem health. The guiding principle is to promote biological tillage through minimizing mechanical soil disturbance and maintaining permanent organic soil cover. We examine evidence of benefits in the context of the wider debate on low-external-input technology. We conclude that CA does not overcome constraints on low-external-input systems and will deliver the productivity gains that are required to achieve food security and poverty targets only if farmers have access to fertilizers and herbicides. We conclude also that widespread adoption of the new paradigm amongst millions of small farmers in order to achieve the 'doubly green revolution' in SSA is subject to the familiar constraints of knowledge transfer and success will depend upon creating innovation networks. Further, we conclude that amongst small-scale farmers partial adoption will be the norm and it is not clear that this will deliver soil health benefits claimed for full adoption of the new paradigm.

Land use in coastal Bangladesh is diverse, competitive and conflicting. Agriculture, shrimp farming, salt production, forestry, ship-breaking yards, ports, industry, settlements and wetlands are some of the uses. Land uses have gone through major changes. Land use in the 1950s had been mainly for paddy cultivation, but salinity intrusion and tidal flooding prevented further intensification. Hence, in the 1960s-1980s, the World Bank and others helped with large-scale polderization in order to boost rice production. A decade later, drainage congestion inside and heavy siltation outside the polders made the southwestern area unsuitable both for agriculture, and, in extreme cases, even for human habitation. However, as the region has a history of traditional shrimp farming, polders provided an opportunity for intensive shrimp farming. Crop land and mangroves were transformed to shrimp farming. This created social conflict. Planned management of diverse land use, including zoning, has been recommended since. This chapter focuses on the complexities of land use in Bangladesh and the adopted institutional approaches.

Although most recharge estimation studies apply multiple methods to identify the possible range in recharge values, many do not distinguish clearly enough between inherent uncertainty of the methods and other factors affecting the results. We investigated the additional value that can be gained from multi-method recharge studies through insights into hydrogeological understanding, in addition to characterizing uncertainty. Nine separate groundwater recharge estimation methods, with a total of 17 variations, were applied at a shallow aquifer in northwest Ethiopia in the context of the potential for shallow groundwater resource development. These gave a wide range of recharge values from 45 to 814 mm/a. Critical assessment indicated that the results depended on what the recharge represents (actual, potential, minimum recharge or change in aquifer storage), and spatial and temporal scales, as well as uncertainties from application of each method. Important insights into the hydrogeological system were gained from this detailed analysis, which also confirmed that the range of values for actual recharge was reduced to around 280-430 mm/a. This study demonstrates that even when assumptions behind methods are violated, as they often are to some degree especially when data are limited, valuable insights into the hydrogeological system can be gained from application of multiple methods.

Over the past 20 years, brackish-water shrimp cultivation in the coastal zone of Bangladesh has contributed increasingly to the national economy, but there is a lack of quantitative data on the effects of shrimp farming at the household and community levels. This chapter investigates the impact of shrimp cultivation on the environment and farmers' livelihood in a typical subdistrict of the coastal zone in Bangladesh. The variables involved with shrimp cultivation and their impact on the land are also taken into consideration and an attempt is made to analyse the patterns of land-use change that occurred between 1975 and 1999. The extensive pattern of shrimp cultivation is achieved by expansion of area rather than by intensification. The expansion of shrimp farming has resulted in decreases in crop production and many environmental problems in the form of a shortage of livestock fodder, fuel scarcity and decreases in traditional labour forces. Under the present circumstances, shrimp cultivation is no doubt beneficial for a selected group of people, but it has negatively affected the livelihoods of landless and marginal farmers, making it difficult for them to survive in the area.

Tanks are small reservoirs, which are widely distributed in South India and Sri Lanka, where they represent an important water resource for people, crops, livestock and fish. Considerable efforts have been made to rehabilitate tank irrigation systems in recent decades, but there have been few studies carried out to improve understanding of their hydrology. This paper presents a daily water balance approach, which aims to simulate the dynamic behaviour of tank storage. The model was validated over four seasons for two representative tanks within Mahaweli System H, a major irrigation system in the dry zone of Sri Lanka. Use of the model to evaluate current performance and scope for improvement is demonstrated.

The coastal zone of the Mekong river delta has experienced rapid economic and environmental changes during the last decade. Given the nature of the environment and the level of dependence on the natural resources base, policies for land and water were very influential in this process. The emphasis on rice created an imperative to control saline intrusion, which was realized through the construction of major engineering works over an extended period (1994-2000). The inertia built up by this process led to a divergence between policy and practice, and adversely affected the livelihoods of fishers and of those farmers who live on aquaculture. This prompted the government to rethink the rice-focus policy, in favor of a land and water policy for balanced rice and aquaculture production. This paper describes an analytical process, which was adopted to explore the feasibility of adopting the new policy for the balanced development of both rice and shrimp production and discusses the impact of the new policy on farmers’ livelihoods.

The coastal environment has undergone rapid change in recent times. Change in the state of the environment is multifaceted, but a key concern is the way that natural habitats -principally mangrove forests and salt marshes -have been extensively cleared and converted to shrimp farming and other uses. The expansion of shrimp farming has also encroached onto agricultural lands. Coastal shrimp farming has been practised for a very long time in some countries as part of the traditional livelihood system, but recent strong demand in global markets, together with technological advances, has fuelled rapid expansion. These rapid, and generally unplanned changes, have provoked conflicts among the three dominant resource-dependent livelihoods in the inland coastal zone: agriculture, shrimp farming and fishing.The coastal zone is characterized by ambiguities of resource ownership and a complex web of interactions among people, resources and ecosystems. Conflicts exist between the drive for short-term financial gain and the desire for long-term sustainable development. Conflicts exist between the priorities of people who derive their livelihoods from aquaculture and those who depend upon agriculture. Conflicts exist between the needs of people who may gain from intensification of land use for agriculture and/or aquaculture and other people (e.g. fisherfolk), whose livelihoods may be adversely affected by environmental impacts. This synthesis chapter presents a discussion of trends, problems and approaches to managing change in the inland coastal zone. We identify key messages from previous research and development experience and consider the supporting evidence for these messages.