1.1. Problem statement
How can 870 million people (FAO, 2009) avoid food insecurity? How are we going to feed an extra two billion people by 2025 (UN, 2009)? Can these objectives be met without exacerbating water scarcity or causing major losses in ecosystem services (Millennium Ecosystem Assessment, 2005)? Water shortage and food insecurity have negative economic consequences, worsen poverty, and affect hundreds of millions of people across Africa, particularly in rural communities in arid and semi-arid areas (UN, 2015). Nine billion people will demand an increase in food production from today's levels by mid-century. With rising food consumption, competition for energy, land, and water will inevitably increase (Park, 2016). Rural production systems will account for a large portion of this output, putting them at the center of the sustainable development agenda (Nicol et al., 2015). Irrigated agriculture presently consumes around 80% of the world’s freshwater, and this level of use will not be sustainable in the future. With expected population expansion, more available water resources, such as rainfall, will need to be used for domestic, municipal, industrial, and environmental demands. However, most of the prevailing poverty and food insecurity in Africa's arid and semi-arid regions is due to rainfall fluctuation and a lack of capability to manage that variability (IWMI, 2015) rather to cumulative annual and seasonal rainfall (Nicol et al., 2015; Rockström and Falkenmark, 2015). Climate change has reduced the length of farming seasons and has forced many smallholder farmers out of production (Ndlovu et al., 2020). Drought and intra-seasonal dry periods are more likely as a result of such erratic patterns, resulting in unpredictable and decreased crop yields, permanent food shortages, widespread poverty, and disruptive conflicts over the use and access to remaining water supplies (Ngigi, 2003).
The issue of land degradation is also one of the most serious concerns threatening agricultural productivity and, as a result, food security. Around 40% of agricultural lands in the globe are moderately degraded, and around 9% are severely degraded, lowering global food productivity by as much as 13% (Mohamed et al., 2019). In dry and semi-arid environments, soil erosion is the primary source of land degradation (Chen et al., 2013; Pena et al., 2020). Soil erosion degrades on-site soil qualities while also causing severe damage off-site (Pimentel and Burgess, 2013). Each year, 75 billion metric tons of soil are lost to erosion, the majority of which comes from sloping lands (Wei and Li, 2006). Soil erosion is predicted to cost the European Union between €0.7 and 14 billion a year (Montanarella, 2007), $37.6 billion in the United States (Uri, 2000), and $400 billion globally (ELD Initiative, 2015). Soil erosion is most commonly thought of as a phenomenon induced by water and wind that redistributes soil throughout the terrestrial environment and carries it to aquatic bodies (Fiener et al., 2018).