How climate and land-use affect future ecosystem services and resilience of mountain grassland

Mountain grasslands were used for mowing and livestock grazing for centuries. Besides their primary use for forage provision, mountain grasslands provide a variety of regulating (e.g. soil stability, water provision, carbon storage) and cultural ecosystem services (e.g. aesthetic and recreational values). Past environmental and land-use changes led to changes in ecosystem services (ES), but it remains unclear which impacts can be expected under further land-use/cover changes and accelerating climate change and little is known about the resilience of ecosystems to provide ES in the face of environmental perturbations. The objective of this study was to map and analyse future impacts on multiple mountain grassland ES and their resilience for a study area in the Central Alps (Stubai Valley, Austria). We considered three different socio-economic scenarios and projected climate variations, and accounted for natural reforestation processes of abandoned grassland as well as for shifts in species composition. Using plant trait-based models at ecosystem level, we quantified six ecosystem services, including forage production, forage quality, carbon storage, soil fertility, water quality, aesthetic value, and their resilience for current and future (years 2050 and 2100) conditions.
At the patch level, forage production was projected to increase by 9 to 18% until 2050 due to a longer growing season, while all other ecosystem services remained unchanged. After 2050, variations in species composition and plant traits resulted in changes to all ecosystem services, with varying change rates. At the landscape level, our results indicate an increase of forage production, carbon storage, and aesthetic value until 2100, whereas forage quality, soil fertility show negative tends under all scenarios. Water quality initially exhibited a negative trend, but turned into a positive trend after 2050. In general, natural reforestation of abandoned grassland had the greatest impacts on ecosystem services, causing a shift from grassland to forest services. Land-use change will have a greater influence than climate change on ES until the middle of the century, whereas climate will become the more important driver for changes in ecosystem services, especially at high altitudes, in the second half of the century. Most of the analysed ES demonstrated high resilience potential under current conditions.
Although all ES maintained their resilience when species composition and plant traits changed over time, most grassland types indicated a higher probability of transformation if resilience is lost. Consequently, management options for mountain grassland might be restricted and decision makers will be faced with the higher vulnerability of ES. The results provide valuable insights to future landscape planning and policies of both socio-economic and environmental dynamics related the management of the landscape and related ES.