NbS-TISE: nature-based solutions tool for assessing the full impact of soil erosion. NC-International integration project for theme 2: assessing net zero plus trade-offs

Marthews, Toby ORCID: https://orcid.org/0000-0003-3727-6468; Feeney, Christopher ORCID: https://orcid.org/0000-0003-2175-1842; Holden, Petra; Onyeagoziri, Assumpta. 2025 NbS-TISE: nature-based solutions tool for assessing the full impact of soil erosion. NC-International integration project for theme 2: assessing net zero plus trade-offs. UK Centre for Ecology & Hydrology, 51pp.

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Abstract/Summary

•Soil erosion is one of the main drivers of land degradation, reducing the resilience of terrestrial ecosystems to future climate change and threatening food security worldwide. Sub-Saharan Africa (SSA) is one of the most adversely affected regions, with 60-80% of people working as smallholder farmers reliant on local agriculture for their livelihoods as well as their direct food supply. Nature-based Solutions (NbS) are often cited as important strategies to mitigate the impacts of global environmental change on land degradation and its impacts. However, their efficacy relies on building an accurate evidence base of likely co-benefits and trade-offs to environment and society (e.g. economic costs, food security and biodiversity conservation). •For this pilot project, we developed a new tool called NbS-TISE (Nature-based Solutions Tool for assessing the full Impact of Soil Erosion). This new tool allows us to efficiently integrate processes of weather and climate, land use change and surface runoff to make robust estimates of soil erosion rates over space and time. The tool was developed through integration of work packages 1B and 2C in the NC-International programme under Theme 2 (assessing Net Zero Plus trade-offs), combining expertise on the JULES land surface model with experience applying the RUSLE soil erosion model in SSA. •Soil erosion routines based on the RUSLE model were coded as a post-processing workflow based on outputs from the JULES model. Because JULES also has existing code structures that can predict the spatial occurrence of surface runoff, this makes it possible to simulate a wider set of erosional processes and sediment transport over the land surface. The model and workflow were then tested over two small catchment areas in South Africa’s Western and Eastern Cape regions where there is an extensive knowledge base of NbS from staff at the African Climate & Development Initiative (ACDI; University of Cape Town). In addition, the InVEST Sediment Delivery Ratio (SDR) model, which uses RUSLE, was used to simulate erosion in these same catchment areas to provide both a comparison against JULES simulation results and additional outputs including the role of land cover and management in inhibiting further erosion and sediment delivery to rivers. •Patterns of soil erosion and sediment yield from existing third-party datasets indicate that soil erosion is generally most severe towards the Eastern Cape and steeper sloping areas in the Western Cape. Our modelling appears to reflect this, albeit, with some subtly different spatial patterns and higher predicted values compared to the South African national RUSLE map from 2008, which most likely stem from our simplified estimates of rainfall erosivity, land cover and management, and the lack of adequate consideration of agricultural and conservation practices in the region, due to a lack of spatially explicit data on these practices. SDR model results highlight that a large proportion of potential soil erosion (assuming a landscape completely bare of vegetation cover) is mitigated by existing land cover and management factors, which will be useful for informing future NbS strategies in the region. Results from the JULES model, conversely, draw attention to additional factors, such as the occurrence of runoff-based erosion in topographic valleys where rainfall is non-negligible. •Through further development and application, the new NbS-TISE tool will be able to provide valuable decision-support information to directly inform on two aspects of Net-Zero-Plus: maintaining a healthy and productive environment and adapting and building resilience to a changing climate. We suggest several key areas to work with other work packages within NC-International and international partners to apply this tool elsewhere, including: across a wider set of catchments in Sub-Saharan Africa, linking with ongoing work in East Africa (WP2C) as well as West Africa (WP3C); within Malaysia and Indonesia (linking with WP2B) to assess the vulnerability of oil palm plantations to soil erosion and flash flooding, particularly the scale of the increased risk compared to naturally forested conditions. •Furthermore, we would look to develop soil erosion capabilities that are more sophisticated than RUSLE alone and include runoff-based processes. This would allow us to address erosion following short, high magnitude weather events (e.g. floods and wildfires) as well as consider additional important processes including river channel changes and gullying. Potential future directions include: integrating MUSLE (a version of RUSLE that uses daily surface runoff instead of long-term rainfall erosivity estimates); integrating a wider ensemble of daily time-stepped erosion models to allow for more robust scenario modelling in future; experimenting with channel erosion modelling routines that can capture processes like riverbank erosion and gullying.

Item Type:	Publication - Report (Project Report)
UKCEH and CEH Sections/Science Areas:	Environmental Pressures and Responses (2025-) Water and Climate Science (2025-)
Funders/Sponsors:	NERC
Additional Information. Not used in RCUK Gateway to Research.:	Full text freely available.
NORA Subject Terms:	Ecology and Environment Agriculture and Soil Science
Related URLs:	Project Website
Date made live:	01 Apr 2025 13:37 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/539194

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