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CO2, Methane, NOx, and POPs have increased due to industrialisation worldwide (fig 1). |
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1 - Atmospheric concentrations of CO2, CH4 and N2O during the last 10,000 years (large panels) and since 1750 (inset panels). Measurements are from ice cores (symbols with different colours for different studies) and atmospheric samples (red lines). The corresponding radiative forcings relative to 1750 are shown on the right hand axes of the large panels (from IPCC 2007) Global atmospheric concentrations of CO2, CH4 and N2O have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years. The atmospheric concentrations of CO2 and CH4 in 2005 exceeded by far the natural range over the last 650 000 years. Global increases in CO2 concentrations are due primarily to fossil fuel use, with land-use change providing another significant but smaller contribution. It is very likely that the observed increase in CH4 concentration is predominantly due to agriculture and fossil fuel use. The increase in N2O concentration is primarily due to agriculture. |
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In contrast to some water limited lowland ecosystems, elevated CO2 did not result in changes in overall biomass production in different alpine plant communities including alpine pioneer vegetation. Yet, there are some small and species specific effects, which may affect the ecosystems in the long run (see lesson B9 for more details):
Soils in arctic and alpine environments often have a high content of organic carbon. Warmer soil conditions will cause a faster organic carbon turnover, probably increasing soil carbon loss, further adding to the CO2 content in the atmosphere. |
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The input of soluble Nitrogen into alpine ecosystems has increased manifold during the last decades. Besides effects on higher plants, especially bryophytes and lichens will suffer from high nutrient concentrations. Bryophytes generally decline under higher nutrient concentrations, which is likely due to complex relationships: Increased nutrient and temperature levels can lead to increased growth rates in bryophytes, as long as water is freely available. Despite increased growth rates, moss mat depth and cover usually decline, probably due to increased decomposition. In addition, the observed changes in growth form under higher nutrient availability go along with a reduced desiccation tolerance in some moss species. Also, lower plants will suffer from the enhanced growth of vascular plants under higher nutrient availability. Alpine lakes and streams are also quite susceptible to nutrient enrichment.
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Semi-volatile persistent organic pollutants (POPs) have been shown to accumulate in cold arctic and alpine regions. As many mountainous regions are found in the vicinity of densely populated and industrialized regions, an additional regional medium-range transport can be assumed. Up to now there is no comprehensive screening of alpine regions concerning the amount and distribution of POPs, but POPs have been found in alpine locations worldwide. POPs tend to accumulate in the food web. The alpine fauna may be particularly strongly affected by POP accumulation because alpine organisms have slower growth rates, often longer life spans, and store more lipids than their counterparts at lower altitude. For example, in alpine fish species and sediment an increase in POP concentrations with increasing altitude has been observed. Elevated POP burdens were also found in mammals like wolverine and birds like alpine osprey.. High levels of POPs can induce disruption of the endocrine, reproductive, and immune systems. Levels found in fish in Canadian mountains are already near critical levels (table 1). |
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Table 1 - Official guidelines (action levels) for POPs in Canadian freshwater fish (Environment Canada) compared with concentration levels found (from Kallenborn 2006) |
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Tropospheric ozone concentrations have increased globally from 20 to between 40 and 50 ppb globally since the beginning of the industrial period. Reaction of ozone in the apoplast with water and solutes leads to the formation of reactive oxygen derivatives, which can have harmful effects on cell structure and function. Many plants in northern regions including trees like Scots pine and birches show negative growth responses to moderately elevated ozone concentrations. Ozone concentrations increase with increasing elevation and vary between regions with different exposure to pollutants and meteorologicalconditions that are favourable for ozone production. Although high-altitude forests experience higher O3 levels than forests at low elevations, it seems that presently, ambient ground-level O3 concentrations do not exert crucial stress on adult conifers at the timberline of the European Alps. O3 fumigation experiments demonstrated that long lasting mean O3 concentrations lower than 100 nL L-1 did not significantly affect the carbon gain of adult Picea abies, Pinus cembra, and Larix decidua trees. This is probably due to the higher antioxidant levels found in timberline trees, which are generally exposed to higher oxidative stress. |
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No or only small responses of plants to enhanced UV have been detected thus far. Yet, aquatic alpine systems are quite susceptible to changes in underwater UV radiation with significant changes in phytoplankton as well as grazer communities. |
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13 August 2018 |
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