Soil erosion in East Africa: an interdisciplinary approach to realising pastoral land management change

Abstract

Implementation of socially acceptable and environmentally desirable solutions to soil erosion challenges is often limited by (1) fundamental gaps between the evidence bases of different disciplines and (2) an implementation gap between science-based recommendations, policy makers and practitioners. We present an integrated, interdisciplinary approach to support co-design of land management policy tailored to the needs of specific communities and places in degraded pastoral land in the East African Rift System. In a northern Tanzanian case study site, hydrological and sedimentary evidence shows that, over the past two decades, severe drought and increased livestock have reduced grass cover, leading to surface crusting, loss of soil aggregate stability, and lower infiltration capacity. Infiltration excess overland flow has driven (a) sheet wash erosion, (b) incision along convergence pathways and livestock tracks, and (c) gully development, leading to increased hydrological connectivity. Stakeholder interviews in associated sedenterising Maasai communities identified significant barriers to adoption of soil conservation measures, despite local awareness of problems. Barriers were rooted in specific pathways of vulnerability, such as a strong cattle-based cultural identity, weak governance structures, and a lack of resources and motivation for community action to protect shared land. At the same time, opportunities for overcoming such barriers exist, through openness to change and appetite for education and participatory decision-making. Guided by specialist knowledge from natural and social sciences, we used a participatory approach that enabled practitioners to start co-designing potential solutions, increasing their sense of efficacy and willingness to change practice. This approach, tested in East Africa, provides a valuable conceptual model around which other soil erosion challenges in the Global South might be addressed.

Bypass and hyperbole in soil research: A personal view on plausible causes and possible remedies

“…Other disciplines, for example cosmology or particle physics, also face enormous challenges, both theoretical and experimental. However, the fact that, in order to address the intimately connected processes occurring in soils, interdisciplinary or transdisciplinary approaches are mandatory (e.g., Blake et al, 2018; Dobrovol'skii, 2006; Pepper, 1996), creates its own set of daunting issues, because the structure of our institutions, the reward systems in place, and the organization of funding agencies, all conspire to discourage the close collaboration of individuals from different disciplines (Baveye, Palfreyman, & Otten, 2014). This huge complexity of soils, in and of itself, undoubtedly accounts for a tendency, by some researchers, to simplify things to make them more manageable, and more amenable to quick publications.…”

Mapping Permanent Gullies in an Agricultural Area Using Satellite Images: Efficacy of Machine Learning Algorithms

“…Globally, soil erosion poses a serious threat to natural and human environments owing to the resulting on-site and off-site problems [2][3][4]. The onsite problems include, but are not restricted to, reduction in soil fertility, loss of soil and nutrients, and destruction of man-made infrastructure (e.g., buildings, roads, bridges), whereas off-site problems include sedimentation of freshwater bodies, which in turn decreases water quality and quantity, leading to loss of freshwater biodiversity [5,6]. These effects further undermine the economic and ecological value brought about by the natural environment to societies.…”

Drivers of increased soil erosion in East Africa’s agro-pastoral systems: changing interactions between the social, economic and natural domains

“…The population in East Africa has experienced an exponential growth from an estimated 6-12 million in the 20s (Anderson 1984;Trewartha and Zelinsky 1954), 24 million in 1950, 56 million in 1980s to 173 million in 2017 (UNDESA 2017). However, scapegoating the problem to overpopulation and overexploitation of natural resources lacks understanding of the complex human-environment interactions and can potentially fuel detrimental policies (Blake et al 2018;Kiage 2013;Lambin et al 2001).…”

“…Many soils in semi-arid East Africa are particularly vulnerable to detachment processes because of a low organic matter content and weak aggregate stability. Furthermore, these soils generate more runoff through the high prevalence of crusting and overall weak structural development (Blake et al 2018;Nishigaki et al 2017). In short, due to the interaction between a distinct sloped topography, high rainfall erosivity, disequilibrium vegetation and fragile soils, catchments in East Africa naturally have high sediment yields (Vanmaercke et al 2014;Walling and Webb 1996).…”