Developing Soil Conservation Strategies with Technical and Community Knowledge in a Degrading Sub‐Humid Mountainous Landscape

Abstract

Worldwide, soil erosion has greatly decreased agricultural productivity and continues unabatedly despite decades of developing sustainability and soil conservation strategies. Current strategies need integrated interdisciplinary perspectives to develop more effective measures, especially in degrading mountainous landscapes where rising sediment concentrations persist. By comparing spatio‐temporal field observations and community perceptions with the Geographic Information System (GIS)‐based universal soil loss equation (USLE), this study critically examined theorized erosion patterns (by USLE) in a degraded landscape (Shanko Bahir, Ethiopia) to improve soil conservation strategy development. Daily hydro‐sedimentological data (showing 792 mm of rainfall leading to 3·2 Mg ha−1 y−1 of sediment yield) revealed mild but variable erosion patterns in 2012. Overlooking hydrology hindered the USLE's suitability for conservation planning. For instance, the median infiltration rate (33 mm h−1) was rarely exceeded (3·5% of events), meaning runoff‐induced erosion risk were not well predicted spatio‐temporally by the USLE R‐factor. Conversely, heterogeneous local perspectives explicitly considered accumulated runoff, saturation (“the water at the top level rests on the bottom”), fertility, and gullies as drivers of erosion (“black soil breaks and forms gorges”). Additionally, they designated steeper mono‐cropped lands as at risk (incidentally also highlighted by USLE). Observational evidence showed steeper midslope areas decreasing in topsoil depth by 14 mm, flatter downslope areas by 0·8 mm, and the mild upslope areas increasing 2 mm. Operationalizing effective soil conservation strategies will require expanding beyond (USLE‐based) technical knowledge to incorporate local stakeholders and consider the main hydrological processes causing erosion in sub‐humid mountainous landscapes: saturated pathways, downslope saturation, subsurface flow, and gully formation. Copyright © 2017 John Wiley & Sons, Ltd.

GUEST EDITORIAL—SPECIAL ISSUE: Mapping and modelling soil erosion to address societal challenges in a changing world

“…The final group of articles documents examples of successful cooperation between scientists and nonacademic stakeholders in research and management planning. Guzman et al (2018) used a combination of hydrological and erosion monitoring, soil erosion modelling, and participatory approaches (group discussion, transect walk, participatory mapping) to evaluate the most suitable methods for soil conservation planning in Ethiopia. Waltner et al (2018) used reports from a farm management system to assess the precision of model‐based soil erosion risk maps in Hungary.…”

Gullies, a critical link in landscape soil loss: A case study in the subhumid highlands of Ethiopia

“…Organized implementation of soil and water conservation (SWC) started in the 1970s after land degradation was identified as the main reason causing famine during periods of drought (Bewket & Sterk, ). Short‐term studies labeled these works as ‘impressive’ but studies that evaluated them over a longer period revealed that while performing well in the semi‐arid regions by increasing water retention (Herweg & Ludi, ; Nyssen et al, ), effectiveness was minimal in the subhumid and humid monsoonal climates (Guzman et al, ). Despite previous experience, in 2010, the government of Ethiopia implemented an extensive nationwide ecological restoration program, which was aimed at doubling agricultural productivity and on enhancing infiltration (Dagnew et al, ).…”

Improving watershed management practices in humid regions

“…Finally, technical solutions for conserving soil will not perform optimally without local input. Farmers have considerable local knowledge and skills that will make any of the proposed practices more suitable and appropriate to their own conditions (Guzman, Tilahun et al, ; Pretty & Shah, ). By strengthening local organizations through participatory processes, practices will better function because detailed information on alternative site‐specific designs for policymakers are currently lacking and these practices will be more sustainable because of ownership by the community (Pretty & Shah, ; Ayele et al, ).…”

“…In Ethiopia, poorly placed soil and water conservation practices are responsible for one third of the erosion loss (Hagmann, ; Haile, Herweg, & Stillhardt, ). This reveals an ongoing and unaddressed gap in our understanding of hydrology, water management, and soil erosion in developing countries and around the world (Forsyth, ; Guzman, Tilahun et al, ; Hoben, ; Stocking, ).…”