Internal report on scenario outputs for long-term assessment regarding climate change resilience, productivity, and environmental impacts - D7.3

Analyses of the historical weather data from 2018 to 2022 in the Niakhar region have revealed irregular patterns characterized by alternating periods of both low and high annual precipitation. This unpredictable variation underscores the importance of carefully evaluating future climate projections to make well-informed decisions regarding future agricultural systems and food production strategies. Future climate projection anomalies of precipitation and air temperature for the Niakhar region used for this assessment were obtained from the global climate model (GCM) compilations of the Coupled Model Inter-comparison Projects (CMIP6), which form the data foundation of the Intergovernmental Panel on Climate Change (IPCC) Assessment Reports.

The modeled precipitation and air temperature were based on the compilation of outcomes of multi-model ensemble (MME) simulations, representing the spectrum and distribution of the most feasible projected changes in the climate system at a monthly spatial resolution. Two shared Socioeconomic Pathway (SSP) climate scenarios, SSP–1.91 and 8.5 for the periods 2020–2039 (near future) and 2080–2099 (far future) were used for this report.

The model scenarios presented in this report (D7.3) centered on diverse management and land-use systems, specifically focusing on the Niakhar MARP report (WP2) and outcomes of innovation platform (IP) meetings where partners have implemented crop–shrub–livestock (CSL) systems. In summary, soil amendment systems involving locally available organic resources (e.g. Guiera s. biomass, cow dung manure), mineral fertilizer, and their mixture applied to Millet (Pennisetum glaucum) - Groundnut (Arachis hypogaea) intercropping systems. In addition, varying planting densities of Guiera s. under pruning practices of managed residue and no residue retention were intercropped with Millet.

These CSL systems were chosen based on their capacity to improve the efficiency of resource utilization, such as biomass production, grain yields, nutrient cycling, and soil organic C accumulation. Moreover, the selected CSL systems are expected to improve resilience to various stresses, such as limited water availability, and rising temperatures. These scenarios were run under the Niakhar historical weather conditions and the projected future climate scenarios of the Niakhar region for ten years using the Land Use Change Impact Assessment (LUCIA) model.

The simulations showed that Millet AGB and grain yield production increased in the long–term under sole organic soil amendments and their combination with mineral fertilizer compared to sole mineral fertilization. This was associated with a decline in SOM under mineral fertilizer-managed soils during the ten-year simulation period. With regard to climate change, a strong negative impact on millet yield, particularly during drought years and the more severe SSP-8.5 scenario was simulated under the longer-term climate trends.

The simulated AGB of Guiera s. increased under the high planting density. Almost all the future climate scenarios decreased the AGB growth of Guiera s. compared to the historical, especially SSP–8.5 (2080-2099). Over the course of the ten–year simulation, SOM increased with increasing Guiera s. planting density for every climate scenario. The positive contribution of residue retention to SOM was only visible under historical conditions. The reasons for these impacts need further investigations.