Changes in pasture productivity may affect potential soil erosion under climate change. The case study of Mera watershed.

The Mera River watershed in the Rhaetian Alps, between Italy and Switzerland, is subject to distributed erosion, and soil degradation, affecting slope stability, and sediment transport in the river. In the future under climate change, erosion is projected to increase especially in winter, as due to larger rainfall share, and smaller snow accumulation. It is therefore necessary to develop best practices for the maintenance of slopes, such as terracing, to reduce erosion and soil loss in the area. We present the results of the recent GE.RI.KO Mera Interreg, and IPCC MOUPA projects.

We first calibrate a hydrological model Poli-Hydro in the study area during 2010-2019, against discharge data, and snow cover area from satellite. Then a Dynamic-RUSLE (D-RUSLE) model is used to simulate spatially distributed soil erosion. The model considers snow melt/accumulation, and the year round dynamics of vegetation. Potential soil erosion is validated against sediment transport data taken in a sample station in the Mera River.

The dynamics of snow cover is simulated using Poli-Hydro, while the C-factor of land cover is corrected using NDVI (Normalized Difference Vegetation Index) from satellite images, accounting for variable vegetation stages, and larger leaf cover (LAI) in summer. The C-factor is further corrected for pasture areas, using productivity data as calculated using the Poli-Pasture model, mimicking pasture growth and biomass productivity. We considered two index species for high/low altitudes, and inter-specific competition.

We then project future scenarios of climate change, and impacts thereby. Six GCMs and four SSPs of the IPCC AR6 are used, to develop 24 climate change scenarios for precipitation and temperature. We also consider changes in CO₂ concentration, and temperature increase, upon land cover, through variation of timberline and growing season. Based upon our results, conservative practices may be devised, to help improvement of pasture productivity, and reduce soil erosion.