Uncertainties in the adaptation of alpine pastures to climate change based on remote sensing products and modelling

Over the last century, the management of pastoral systems has undergone major changes to meet the livelihood needs of alpine communities. Faced with the changes induced by recent global warming, the ecological status of many pastoral systems has seriously deteriorated in the western alpine region. We assessed changes in pasture dynamics by integrating information from remote-sensing products and two process-based models, i.e. the grassland-specific, biogeochemical growth model PaSim and the generic crop-growth model DayCent. Meteo-rological observations and satellite-derived Normalised Difference Vegetation Index (NDVI) trajectories of three pasture macro-types (high, medium and low productivity classes) in two study areas -Parc National des ' Ecrins (PNE) in France and Parco Nazionale Gran Paradiso (PNGP) in Italy -were used as a basis for the model cali-bration work. The performance of the models was satisfactory in reproducing pasture production dynamics (R2 = 0.52 to 0.83). Projected changes in alpine pastures due to climate-change impacts and adaptation strategies indicate that: i) the length of the growing season is expected to increase between 15 and 40 days, resulting in changes in the timing and amount of biomass production, ii) summer water stress could limit pasture produc-tivity; iii) earlier onset of grazing could enhance pasture productivity; iv) higher livestock densities could in-crease the rate of biomass regrowth, but major uncertainties in modelling processes need to be considered; and v) the carbon sequestration potential of pastures could decrease under limited water availability and warming.

Automated summary

Over the past century, pastoral systems have experienced significant changes in management to meet the livelihood needs of alpine communities. However, global warming has resulted in a serious decline in the ecological status of pastoral systems in the western alpine region. Using remote-sensing products and process-based models, we evaluated changes in pasture dynamics and projected the impacts of climate change on alpine pastures. The findings suggest that the growing season will lengthen, water stress may limit productivity, earlier grazing onset could enhance productivity, higher livestock densities may increase biomass regrowth, and carbon sequestration potential could decrease due to limited water availability and warming.