SOIL-SAFE: Employing archaeological insights in the co-design of agricultural soil erosion mitigation

Soil health is fundamental to agricultural production and by extension to ensuring food security and achieving the UN Sustainable Development Goals, particularly SDG 2 (Zero Hunger) and SDG 15 (Life on Land). Where soil is at risk of erosion, measures are often put in place to prevent it, most commonly by the construction of agricultural terracing designed to stop erosion before it occurs and thus preserve soils in situ. However, archaeological research from Tanzania and Ethiopia demonstrates that food security was achieved in the past by initially allowing soil erosion to occur - and perhaps even encouraging it - since this permitted the capture of eroded soils in river-side sediment traps. This has several important benefits, because sediments transported and deposited by water are fine in texture making them easy to till and for roots to penetrate, whilst repeated depositions lead to the accumulation of deep deposits of fertile sediments in irrigable locations and enable prolonged irrigation without salinization - a common problem in irrigated soils. Indeed, in the ancient examples examined in Tanzania and Ethiopia salinization was avoided for centuries. The sediment traps may thus represent historic examples of the recent concept of 'land degradation neutrality' that is integral to SDG 15: degradation in one part of the landscape is mitigated by increases in capacity elsewhere. Sediment traps could therefore act as models for sustainable agricultural development, but to fully assess this it is essential to quantifying the trade-offs between erosion losses and the benefits of sediment capture. Building on relationships with agricultural NGOs in the UK, Europe and eastern Africa, this partnership will combine archaeological, ethnobotanical and development studies research to co-design an interdisciplinary method of assessing the costs and benefits of sediment traps that can be applied by NGOs and researchers (either jointly or separately), and which is sufficiently flexible to be applicable in a range of social and ecological environments worldwide.