Einfluss von Klimawandel und Nutzungsaufgabe auf Vegetation und Landschaft im Oberengadin (Schweizer Alpen) in den kommenden 100 Jahren.
Krüsi, Bertil O. (2007). Einfluss von Klimawandel und Nutzungsaufgabe auf Vegetation und Landschaft im Oberengadin (Schweizer Alpen) in den kommenden 100 Jahren. . In: W. Haeberli; F. Keller; Bertil O. Krüsi; al. et (Hg.). GISALP. Raum-zeitliche Informationen über schnelle Klimaänderungen in hochalpinen Umweltsystemen als strategisches Werkzeug für Analyse, Kommunikation, partizipative Planung und Managment im Tourismusgebiet Oberengadin. (S. 69-88). Zürich: vdf. Peer reviewed.
Impacts of global warming and land abandonment on vegetation and landscape in the Upper Engadine valley (Swiss Alps) during the coming 100 years
• During the coming 100 years, two main driving forces will change the Alpine landscape, viz. (1) global warming and (2) land abandonment. Glaciers and permanent snow will melt back and forests will reclaim abandoned land.
• These two forces will affect primarily four habitats, viz. (1) glacier-forelands (2) snowline ecotones, (3) subalpine pastures and (4) timberline ecotones.
• First and foremost, the alpine landscape will be affected by the climate-induced deglaciation, producing pristine terrain, which for long periods of time will be covered mainly by gravel and rock (primary succession). Second and already much less conspicuously, the forest will slowly reclaim subalpine pastures, which after centuries of heavy grazing are now increasingly abandoned (secondary succession). In the timberline ecotones, finally, tree rejuvenation will benefit only in the very long term from the combination of reduced grazing and global warming.
• In the foreland of the Sesvenna-glacier located far above the timberline at 2700 m a.s.l., 70 years after deglaciation vegetation cover (vascular plants, bryophytes and lichens) attained on average merely 20%, i.e. a value substantially below the 85% observed in adjacent alpine grassland.
• At subalpine altitudes, primary succession proceeds significantly more quickly. In the foreland of the Morteratsch-glacier at 2000 m a.s.l., for instance, 70 years after deglaciation the herb and shrub layers covered average 50% and 20%, respectively.
• The tree layer, which is particularly important for the perception of the landscape by man, on the other hand, develops only late during primary succession. In the foreland of the Morteratsch-glacier, even 100 years after deglaciation trees attaining a height of 4 m or more covered less than 5%, as compared to a crown cover of about 40% in forest stands outside the glacier foreland.
• The same holds true for secondary succession on abandoned subalpine pastures. According to the model used, Alp Surlej (2070 m a.s.l.) will still be largely free of trees even 175 years after abandonment, whereas the diversity of vegetation and flora will decrease markedly already 50 to 100 years after abandonment.
• Up-to-now, there is no evidence for a substantial and widespread climate-induced acceleration of primary or secondary succession in the Upper Engadine. However, one of the two Salix-species studied seems to have responded to recent climate change by producing wider tree rings.
• Up-to-now, it seems that global warming has not substantially accelerated either primary or secondary succession in the Upper Engadine valley. However, there is evidence that one Salix-species may have responded to recent global warming by accelerated growth.
• For the Upper Engadine valley, we conclude that during the coming 100 years the landscape outside the settlements and the valley floor will change primarily due to global warming. The climate-induced retreat of glaciers and permanent snow will create large gravel-covered areas, which are only slowly colonized by plants and animals. Land-use changes, namely the retreat of man from alpine and subalpine pastures, on the other hand, will presumably affect the landscape only little.