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The factsheets describe 13 electricity supply alternatives that could contribute to the Swiss electricity mix in 2035: (1) three hydropower types, including large dams, large run-of-river, and small hydropower; (2) five new renewable technologies—solar cells (photovoltaics), wind, deep geothermal, woody biomass, and biogas; (3) nuclear power; (4) waste incineration and large natural gas power; (5) net electricity import from abroad (net on the annual basis); and (6) electricity savings and efficiency improvements to reduce the electricity demand. Each technology, its current status, resource potential, and environmental, health, and economic impacts were described qualitatively and quantitatively. The impacts included climate change (CO2equiv); local air pollution (PM10equiv; SOx and NOx); water, landscape, and land use (m2 of land use); flora and fauna; accidental impacts, resource use, and waste (kWh of nonrenewable energy used for 1 kWh of electricity); electricity costs (rappen (Rp.) per kWh); and electricity supply reliability. The impacts were assessed using data from literature, prioritizing the Swiss-specific data as much as possible and including qualitative explanations for non-experts. The factsheets are accompanied by a glossary and a supplementary overview table that applied a five-color indicator system to reflect the severity of impacts across technologies. The factsheets were developed for an informed citizen panel study in July 2017 in Switzerland, described in the following publication: Volken, S.; Xexakis, G.; Trutnevyte, E. Perspectives of Informed Citizen Panel on Low-Carbon Electricity Portfolios in Switzerland and Longer-Term Evaluation of Informational Materials. Environmental Science & Technology 2018 52 (20), 11478-11489, DOI: 10.1021/acs.est.8b01265

Arbeitsberichte Verkehrs- und Raumplanung, 269

Nach der letzten Maximalvereisung (LGM) Nord-Amerikas und N-Europas vor etwa 20.000 Jahren begannen die Eisschilde abzuschmelzen. Im Spätglazial, das um 10.000 BP endete, erfolgten noch letzte kleine Gletschervorstöße und um 13.000 BP begann die Wiederbewaldung der Alpen. Zu Beginn des Holozäns setzte eine schnelle Erwärmung mit raschem Anstieg der Waldgrenze bis über 2.100 m Meereshöhe ein. Diese Wärmegunst war bedingt durch die größte Nähe der Sonne zur Erde im Nordsommer, wodurch die N-Halbkugel von ca. 9.000-5.000 BP an der Obergrenze der Erdatmosphäre ca.7% mehr Sonnenenergie erhielt und dadurch bis zu 2 K wärmer als heute war. Diese rund 4.000 Jahre dauernde Wärmeperiode mit um 1-2 K höheren Jahresmitteltemperaturen, das mittelholozäne sogenannte Klimaoptimum (Hypsithermal), wurde durch fünf Kaltphasen mit Waldgrenzeabsenkungen von ca. 100 Höhenmetern und Gletschervorstößen unterbrochen. Um 8.000-5.500 BP lag im Wärmeoptimum (Atlantikum) die Waldgrenze bis in Höhen von 2.300-2.400 m, d.h. 80-100 Höhenmeter über der heutigen Position. Nachdem im Mittleren Subboreal um ca. 4.000-3.700 BP die Waldgrenzen nochmals höchste Lagen erreichten, folgten um 3.500-3.100 BP und 2.830-2.270 BP Waldgrenzeabsenkungen von 40-100 m sowie Gletschervorstöße in den Ost- und Zentralalpen. Zwischen der römerzeitlichen Klimagunst und der hochmittelalterlichen Wärmeperiode folgte eine Abkühlung mit erneuten Gletschervorstößen und Waldgrenzeabsenkungen, die sich mit zunehmenden anthropogenen Einflüssen überlagern. Die Kleine Eiszeit (ca. 1320-1850 AD) war gekennzeichnet durch markante Gletschervorstöße und häufigere Unwetter mit Wirkung auf das sozio-ökonomische und kulturelle Leben. Holocene climate variations and timber line fluctuations of in the Alps: After the last glacial maximum (LGM) in N-America and N-Europe, the large ice shields started to melt. After the last smaller glacier advances reforestation started at about 13,000 BP in the Alps, and the full glacial period ended at 10,000 BP. At the onset of the Holocene, climate warming started quickly and the forests reached ca. 2,100 m a.s.l. This warmth period, caused by the perihelion of earth during the boreal summer, lead to higher solar radiation by about 7%. from ca. 9,000-5,000 BP warmring the Earth’s surface by up to 2 K. This Mid-Holocene climate optimum (hypsithermal interval) lasted 4,000 years with annual average temperatures 1-2 K higher, but it was interrupted by five cooler periods with a lowering of timber line by up to 100 m and glacier advances. During the climate optimum (Atlantic) from 8,000- 5,500 BP the forests reached their highest levels with 2,300-2,400 m a.s.l., i.e. 80-100 m higher than their actual position. After the last high forest positions during the Mid-Subboreal at ca. 4,000-3,700 BP followed a lowering by 40-100 m in the Eastern and Central Alps and glacier extensions due to cooler conditions from 3,500-3,100 and 2,830-2,270 BP. Between the warm periods of Roman Times and Early Middle Ages, a cooler period led to glacier advances and a lower timber line, overlapping with an increasing human impact. During the Little Ice Age (ca. 1,320-1,850 AD) marked glacier advances and extreme weather affected social, economic and cultural life.

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.