Synergies and trade-offs between ecosystem services in an alpine ecosystem grazed by sheep – An experimental approach

• Published in: Basic and applied ecology 2016-11, Vol.17 (7), p.596-608
• Main Authors: Austrheim, Gunnar, Speed, James D.M., Evju, Marianne, Hester, Alison, Holand, Øystein, Loe, Leif Egil, Martinsen, Vegard, Mobæk, Ragnhild, Mulder, Jan, Steen, Harald, Thompson, Des B.A., Mysterud, Atle
• Format: Article
• Language: English
• Subjects: Biodiversity; Carbon capture and storage; Density; Ecosystem services; Ecosystems; Grazing; Habitats; Herbivory; Livestock; Management; Mountains; Optimal stocking levels; Overgrazing; Sheep; Threshold
• ISSN: 1439-1791
• DOI: 10.1016/j.baae.2016.06.003

Domestic livestock drives ecosystem changes in many of the world's mountain regions, and can be the dominant influence on soil, habitat and wildlife dynamics. Grazing impacts on ecosystem services (ES) vary according to densities of sheep, but an ES framework accounting for these is lacking. We devised an experiment to evaluate synergies and trade-offs of ESs and components of biodiversity affected by sheep density at the alpine landscape scale in southern Norway. We examined the effects of increased (80 per km2), decreased (0 per km2) and maintained sheep densities (25 per km2) on ‘supporting’, ‘regulating’ and ‘provisioning’ services and biodiversity (plants, invertebrates and birds). Overall, ESs and biodiversity were highest at maintained sheep density. Regulating services, including carbon storage and habitat openness, were particularly favoured by maintained densities of sheep. There was no overall decline in ESs from maintained to increased sheep densities, but several services, such as runoff water quality, plant productivity and carbon storage, declined when grazing increased. Our study provides experimental evidence for a positive effect of grazing on ES, but only at maintained low sheep densities. By identifying ES and biodiversity components that are traded-off at decreased and increased grazing, our study also demonstrates some of the negative impacts on ecosystems that can occur in mountain regions if management does not regulate herbivore densities. Viehhaltung bewirkt in vielen montanen Regionen der Welt Veränderungen am Ökosystem und kann der dominante Einfluss auf die Dynamik von Böden, Habitaten und Wildtieren sein. Die Einflüsse der Beweidung auf Ökosystemdienstleistungen variieren mit der Dichte von Schafen, es fehlt aber ein System der Ökosystemdienstleistungen, das dies berücksichtigt. Wir entwarfen ein Experiment, um die Synergien und Zielkonflikte zwischen Ökosystemdienstleistungen und Biodiversitätskomponenten zu erfassen, die durch die Schafdichte in alpinen Landschaften in Südnorwegen beeinflusst werden. Wir untersuchten die Effekte von erhöhter (80 Ind./km2), verringerter (0 Ind./km2) und beibehaltener Schafdichte (25 Ind./km2) auf “Unterstüt- zungs-”, “Regulations-” und “Versorgungsdienstleistungen” sowie auf die Biodiversität (Pflanzen, Wirbellose, Vögel). Insgesamt waren die Ökosystemdienstleistungen und die Biodiversität bei beibehaltener Schafdichte am höchsten. Regulationsleistungen wie Kohlenstoffspeicherung und Offenhei