Soil erosion and sediment transport in Tanzania: Part II – sedimentological evidence of phased land degradation

Abstract

Soil resources in parts of Tanzania are rapidly being depleted by increased rates of soil erosion and downstream sediment transport, threatening ecosystem health, water and livelihood security in the region. However, incomplete understanding to what effect the dynamics of soil erosion and sediment transport are responding to land-use changes and climatic variability are hindering the actions needed to futureproof Tanzanian land-use practices. Complementary environmental diagnostic tools were applied to reconstruct the rates and sources of sedimentation over time in three Tanzanian river systems that have experienced changing land use and climatic conditions. Detailed historical analysis of sediment deposits revealed drastic changes in sediment yield and source contributions. Quantitative sedimentation reconstruction using radionuclide dating showed a 20-fold increase in sediment yield over the past 120 years. The observed dramatic increase in sediment yield is most likely driven by increasing land-use pressures. Deforestation, cropland expansion and increasing grazing pressures resulted into accelerating rates of sheet erosion. A

Soil erosion and sediment transport in Tanzania: Part I – sediment source tracing in three neighbouring river catchments

“…Since river catchments systems are dynamic, they have variable amounts of discharge, sediment transport and source contributions (Lizaga et al, 2019(Lizaga et al, , 2020a. This is especially so in the context of semi-arid East Africa, which is further explored in the paired article of Wynants et al (2021). The lack of high temporal resolution sampling is thus a major source of uncertainty in this study.…”

“…How to cite this article: Wynants, M., Munishi, L., Mtei, K., Bodé, S., Patrick, A., Taylor, A. et al (2021)…”

“…Estimations of source zone contributions to riverine sediment are particularly valuable for designing targeted management interventions to maintain both soil health and water quality. This article is the first part of an article pair, wherein the second article studies the changes in soil erosion and sediment transport in the region over the past 120 years (Wynants et al, 2021).…”

Evolution and copula modelling of drought duration and severity over Africa using CORDEX‐CORE regional climate models

“…Several studies on drought have been conducted in East Africa, West Africa and South Africa (Ogunjo & Olusola, 2022; Orimoloye et al, 2022; Sivakumar, 1991). In East Africa and other parts of SSA, access to freshwater is in a very critical state as a result of drought (Ntale & Gan, 2003; Orimoloye et al, 2022; Thomas et al, 2021; Verschuren et al, 2000) and other factors such as but not limited to sedimentation (Ashley et al, 2004; Reed & Cumberlidge, 2006), pollution, land degradation (Maitima et al, 2009; Stahl et al, 1993; Wynants et al, 2021), high rates of evaporation from Lake Victoria (Nicholson et al, 2021; Yin et al, 2000; Yin & Nicholson, 1998) and the anoxic situation in Lake Tanganyika (Huc et al, 1990; Nahimana et al, 2008; Rudd, 1980). In Southern Africa, most countries such as South Africa, Botswana, Namibia and Zimbabwe present a lower than global average mean annual precipitation (Shongwe et al, 2009) that impacts rainfall–runoff relationships, economic growth and hydrological cycle dynamics.…”

Building Climate Change Adaptation and Resilience through Soil Organic Carbon Restoration in Sub-Saharan Rural Communities: Challenges and Opportunities

“…In East Africa, soil loss has been largely attributed to erosion by water with an estimated mean soil loss of around 6.3 t/ha/yr, half of which is likely to be derived from croplands [7]. Efforts to reduce erosion by water must consider landscape connectivity in a holistic manner, which considers social and economic frameworks alongside an understanding of landscape hydrology [8][9][10]. Crucially, assessment and development of sustainable land management (SLM) must be embedded within a participatory approach, drawing on local knowledge and building practical systems of change from within the local community, ultimately fostering community-led management, which is not reliant upon but supported by external services [10][11][12][13][14][15].…”