Traps and transformations : Exploring the potential of water system innovations in dryland sub-Saharan Africa

Detta är en avhandling från Stockholm : Department of Systems Ecology, Stockholm University

Sammanfattning: In semi-arid and dry sub-humid sub-Saharan Africa (SSA), high poverty levels and a heavy reliance on small-scale rainfed agriculture make rural livelihoods difficult. Upgrading current farming systems, in a way that safeguards productivity beyond field-scale, is urgent. This thesis builds on a case study of the Makanya catchment in Tanzania, and focuses on the potential of small-scale water system innovations (SWSIs), such as rainwater harvesting and conservation tillage, for increasing on-farm productivity while supporting multi-functional landscapes. The thesis consists of five papers that approach questions of alternative development trajectories for smallholder agro-ecosystems, and effects of SWSIs on key system variables, from varying perspectives. Paper I presents a conceptual model for interpreting multi-equilibrium dynamics in dryland agro-ecosystems, and analyzes Makanya's development over the past 50 years. Paper II investigates farmers' strategies to deal with drought and the impact of a local supplemental irrigation system on coping capacity. Paper III studies the effects of conservation tillage on yields and soil properties. Paper IV explores a set of future scenarios for the catchment. Paper V maps dryspell frequency and trends over time in a drylands-in-SSA perspective. The results show that smallholder farmers in agro-ecosystems such as Makanya depend on a wide array of on- and off-farm ecosystem services. The productivity of the surrounding landscape is especially important when crops fail. Furthermore, dryspells are a major constraint in these systems. In Makanya long dry-spells have become twice as common over the past 50 years, and frequently cause crop failures. This is a driver for land degradation, and maintains a climate-related poverty trap. SWSIs provide opportunities for dryland farmers to shift their agro-ecosystems to more productive trajectories through a number of mechanisms, including lowered crop failure frequency, altered on-farm water balances, and improved soil quality. Although this is promising, the task of transforming these systems is complex. For SWSIs to be effective, prerequisites are farming system solutions that integrate water- and nutrient management, and broad-based investments that focus on a much wider range of issues than only the water management technology. Moreover, given the uncertain future, investments in small-scale farming should be designed so that they benefit local communities across a range of pathways. Participatory scenario planning is useful both for identifying robust investment strategies and for navigating towards desirable development trajectories.

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