ateam - Potsdam Institute for Climate Impact Research
ateam - Potsdam Institute for Climate Impact Research
ateam - Potsdam Institute for Climate Impact Research
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ATEAM final report Section 5 and 6 (2001-2004) 35<br />
frequency of floods caused by the snowmelt alone. However, it is difficult to achieve reliable estimates<br />
of daily peak flows under changed climate conditions, as the currently available state-of-the-art climate<br />
scenarios only give a very rough estimation of future daily precipitation.<br />
Tourism and recreation in the mountains<br />
Snow cover, an indispensable prerequisite <strong>for</strong> winter tourism, is highly sensitive to changes in<br />
temperature. Simulations indicate that the elevation of a reliable snow cover will rise between 200 m<br />
and 400 m, i.e. from about 1300 m a.s.l. 22 today to 1500-1700 m a.s.l. at the end of the 21 st century<br />
(Figure 29). The predicted increase in winter precipitation can partly compensate <strong>for</strong> the temperaturerelated<br />
rise of the snow line, but it cannot prevent the upward shift. At present, about 85% of all Swiss<br />
ski areas still have sufficient snow. A 300 m rise of the snow line, however, would reduce this to about<br />
63% (cf. Elsässer & Messerli, 2001). Sensitivity studies <strong>for</strong> the five catchments have shown that the<br />
elevation of reliable snow cover moves upward by approximately 150 m per degree Celsius of warming.<br />
An analysis of the number of summer heat days revealed that particularly in the southern Alps heat<br />
days become more frequent, which likely reduces the attractiveness of this area <strong>for</strong> a range of outdoor<br />
activities such as hiking or biking. In the northern Alps, only a slight increase in the number of heat days<br />
was found. Regarding the number of rainy days, the analysis showed no significant change.<br />
Carbon storage in mountain vegetation<br />
Simulating the impact of climate and land use change on carbon storage in the vegetation, it became<br />
clear that land use change is the dominating process at the local scale (100 m to 1000 m). The alpine<br />
catchments under investigation show strong local signals in carbon emission or uptake depending on<br />
the land use scenarios (Figure 30), which predict changes in <strong>for</strong>est area by up to ±25%.<br />
Compared to changes in land use, climatic shifts only marginally affect this ecosystem service at the<br />
local scale. However, climate becomes more relevant at the catchment scale. Figure 31 shows the<br />
development of vegetation carbon storage averaged over the catchment areas <strong>for</strong> the four ATEAM time<br />
slices. According to the model calculations, the biosphere currently acts as a sink. This sink slightly<br />
increases in the second time slice. This is mainly driven by the extension of the <strong>for</strong>ested area<br />
(abandonment of alpine pastures) and by the temperature-related increase in carbon stock at high<br />
elevations. In the third and fourth time slice, however, this sink weakens or even becomes a source <strong>for</strong><br />
some scenarios, as carbon stocks at low elevations decrease caused by amplified respiration. However,<br />
these results are subject to considerable uncertainties, as carbon cycling, particularly respiratory<br />
processes at high elevations is so far not fully understood, the model was not validated at high lying<br />
plots, and changes in plant functional type and tree migration to higher regions is not included in this<br />
simulations.<br />
A number of papers to be submitted to peer-reviewed journals like Water Resources <strong>Research</strong> and<br />
Ecosystems are currently being prepared (see Annex 2).<br />
6.2.3 Adaptation (WP1 and 5)<br />
Adaptation is any adjustment in natural or human systems in response to actual or expected<br />
environmental change, which moderates harm or exploits beneficial opportunities (IPCC 2001).<br />
Adaptation can be autonomous and planned. Autonomous adaptation is “triggered by ecological<br />
changes in natural systems and by market or welfare changes in human systems, but does not<br />
constitute a conscious response to environmental change” (IPCC 2001). Autonomous adaptation<br />
changes sensitivity by changing a system’s state. In other words, it is part of the internal feedbacks in<br />
the human-environment system and its subsystems like ecosystems and markets, such as when <strong>for</strong>est<br />
tree species extent their bioclimatic range due to evolutionary adaptation, or the demand is slowed in a<br />
market after price increase resulting from supply shortages. However, ecosystem models are currently<br />
22 m a.s.l. = meters above sea level.