Land-based climate change solution options for Sahelian West Africa from land-used and land-cover model

Abstract

Assessing the impacts of anthropogenic land use and land cover change (LULCC) on climate extremes is crucial for understanding the complex interactions between the land surface and the atmosphere, significantly influencing regional climate dynamics. Therefore, the study is essential in Sahelian West Africa, where rapid population growth, desertification, and agricultural expansion intensify environmental changes and amplify climate variability and extremes. Despite numerous studies, there needs to be more consensus on the regional effects of LULCC on climate extremes in West Africa. This research provides the first multidisciplinary systematic review of biophysical LULCC impacts in West Africa. Additionally, high-resolution (15 km) LULCC simulations spanning 2012 to 2022 were performed to investigate these effects in Sahelian West Africa, using a fully coupled Weather Research and Forecasting (WRF-Only) system integrated with the Noah-MP land surface model with dynamic vegetation. Also, the WRF for hydrological forecasting (WRF-Hydro) system was employed, coupled with Noah-MP. These experiments aimed to elucidate the potential impacts of anthropogenic LULCC on regional climate extremes, providing critical insights into land-atmosphere interactions in this vulnerable region. Results indicate that deforestation contributes to regional warming, with significant historical temperature increases of +0.26 ± 0.12 °C and projected increases of +0.88 ±0.25 °C under future scenarios. Conversely, afforestation could significantly cool the climate, reducing temperatures by -0.24 ± 0.14 °C historically and -0.22 ± 0.14 °C in future scenarios, excluding carbon sequestration effects. Deforestation historically decreases regional precipitation by -47.45 ± 29.2 mm/year and -55 ± 102.2 mm/year under future scenarios. In contrast, large-scale afforestation could substantially mitigate droughts, increasing precipitation by +200 ± 124 mm/year historically and +635 ± 521 mm/year in future projections. Analysis of 12 climate indices (mean and extreme) reveals that LULCC negatively affects temperature extremes, with modest average warming. This effect is more pronounced in WRF-Hydro simulations (+2.6%) compared to WRF-Only simulations (+1.88%). Similarly, precipitation increases are more significant in WRF-Hydro (+4.86%) than in WRF-Only (+3.16%). Extreme climate indices demonstrate greater sensitivity to LULCC than mean conditions. The findings emphasize the critical role of hydrological processes in WRF-Hydro, which improves model performance, contributing up to +0.95% for temperature and +2.45% iii for precipitation on average. Exceptions are seen in TXn and CCD indices, where hydrological contributions decrease by -0.3%. Land surface temperature shows a maximum increase of up to +0.5 K with WRF-Only and +0.6 K with WRF-Hydro during the wet-to-dry seasonal transition (August to January), primarily driven by reduced plant transpiration (ΔEt) due to decreased canopy foliage. Over the entire year, LULCC induces a slight rise in land surface temperature (<0.3%) in both WRF-Only and WRF-Hydro simulations, with a marginally stronger response in WRF-Hydro. These findings underscore the importance of fully coupled modelling frameworks that integrate the complexities of LULCC and land-atmosphere interactions. Such approaches are essential for effectively evaluating land-based mitigation strategies, enhancing regional climate resilience, and supporting improved livelihoods in Sahelian West Africa.