Recent climate change is beginning to affect all life on Earth. Its impacts differ from region to region, from one ecosystem, life form, or species to another. The detection of the ecological impacts caused by warming require a variety of means ranging from remote sensing to field-based long-term studies.
Climate change impacts may be masked or enhanced by other direct and indirect anthropogenic impacts, such as landscape fragmentation, habitat conversion and species invasions. Yet, remote areas little affected by human population pressure, such as many alpine summits, can provide an ideal 'natural laboratory' for ecological research of climate impact.
While species richness may be increasing at regional scales in many parts of the world, mostly through the introduction of exotic species, at the global scale, biodiversity is decreasing (SAX & GAINES 2003). There are warnings that a major wave of extinction, driven by economic activity is underway at rates 100-1000 times higher than considered to be natural (WARDLE 1999; GITAY et al. 2002; HARE 2003).
In addition, in the near future, climate change could act as a major cause of extinction in a range of semi-natural and natural environments. A recent estimate predicts, on the basis of mid-range climate warming, that 15-37% of the species could become 'committed to extinction' in their globally distributed sample regions by 2050 (THOMAS et al. 2004).
Alpine environments are areas lying between the altitudinal treeline, or its substitutes, and the altitudinal limits of life. This 'alpine life zone' is dominated by low stature and largely long-lived vegetation. The alpine life zone is globally distributed, from polar to tropical latitudes and occurs across oceanic and continental climates.
Many alpine regions are among the remaining most pristine environments on earth. Even though direct human land use has affected alpine areas relatively little, today's climate warming may result in the reduction of its current extent, and in some cases, its continued existence.
Climate warming can upset the growth of cold-adapted species, and more importantly, may impose competition on alpine plants from species from lower elevations. On many mountains, increasing temperature could force alpine plants to migrate upwards until they reach the highest elevations (summit trap phenomenon). Many mountain ranges which host a large number of endemic plants are very likely to suffer critical species losses (THEURILLAT & GUISAN 2001; HALLOY & MARK 2003; PAULI et al. 2003; PICKERING & ARMSTRONG 2003). Climate-induced differential migration rates could lead to the formation of new plant assemblages and result in changes in ecosystem functioning (ROOT et al. 2003).
Owing to the compression of thermal zones and to isolation caused by low-temperature conditions, high mountains host a high number of species, including many endemic species with a local distribution. The alpine plant diversity is estimated to higher than the global average (KÖRNER 1999). In Europe, for example, alpine environments cover only 3 % of the continent's area, however, about 20 % of all native European vascular plants may be found there (VÄRE et al. 2003). Hence, climate change-induced threats to alpine plant diversity impact on a significant part of the planet's natural heritage.
Evidence of climate-induced upward migration of mountain plants has already been detected. Increased mountain forest growth or advances of altitudinal treelines have been reported from several mountain ranges in Europe (Bulgaria, MESHINEV et al. 2000; Urals, MOISEEV & SHIYATOV 2003; Scandes, KULLMAN 2002; 2003), in North America (STURM et al. 2001), and in New Zealand (WARDLE & COLEMAN 1992). Increases in alpine species richness have been reported from the Alps (HOFER 1992; GRABHERR et al. 1994; GRABHERR et al. 2001; PAULI et al. 2001; BAHN & KÖRNER 2003) and from Scandinavia (KLANDERUD & BIRKS 2003).These observations indicate that alpine vegetation and the distribution limits of its species do respond to climate change despite the long-lived and slow-growing nature of alpine plants. Climate warming has now reached a level where substantial ecological impacts can be easily detected in alpine and arctic environments around the world (KULLMAN 2004).
Assuming an average lapse rate of 0.6°C per 100 m elevation, a mid-range warming of 3 °C could cause current distribution limits shift by 500 m. As a result, the alpine zone of many mountains ranges could potentially disappear. Observed treeline rises of up to 150-165 m in Scandinavia during the 20th century reflect the 1°C summer warming during that period (KULLMAN 2004).
The rates of upward establishment of some alpine species in the 20th century were calculated to be about 1 to 4 m per 10 years, indicating a significant time lag to the measured temperature increase (GRABHERR et al. 1995). Models predict a pronounced increase of alpine grassland species at the expense of other cold-adapted alpine and nival plants (GUISAN et al. 1998; GOTTFRIED et al. 1999, 2002).
Yet, it is unknown if the rates of upward establishment of species will rapidly increase above a certain climatic threshold. Furthermore, for most alpine species there is no data about changes in their altitudinal distribution. Despite the large number of studies, no comprehensive account about the rate of the retreat of the alpine world exists. The scarcity of information about species range extensions and species displacements is likely to reflect the lack of historical baseline records rather than a lack of actual change.
Meteorologists and glaciologists have data series spanning several decades and sometimes dating back as far as the 19th century (BARRY 1992; HAEBERLI et al. 1996). No such ecological data sets are available, apart from rare exceptions. The increasingly apparent ecological impact of climate change in alpine environments, however, makes an effective long-term observation strategy indispensable. Not only for the documentation of biodiversity and habitat changes, but as a prerequisite for model verification and risk assessment. This urgent demand for a ground-based monitoring is also manifest in numerous research recommendations (e.g., MESSERLI & IVES 1997; EEA 1999; HEAL 1999; BECKER & BUGMANN 2001; KÖRNER & SPEHN 2002; PRICE & NEVILLE 2003). The GLORIA network was established to address this need. Launched in 2001, it has already made much progress towards the implementation of a standardised alpine long-term observation network on the global scale.
BAHN, M. & KÖRNER, C., 2003: Recent increases in summit flora caused by warming in the Alps. In NAGY, L., GRABHERR, G., KÖRNER, C. & THOMPSON, D. B. A. (eds.), Alpine Biodiversity in Europe - A Europe-wide Assessment of Biological Richness and Change. Ecological Studies 167, Springer, Berlin: 437-441.
BARRY, R. G., 1992: Mountain Weather and Climate. 2 ed. Routledge, London: 402 pp.
BECKER, A. & BUGMANN, H., 2001: Global Change and Mountain Regions. The Mountain Research Initiative. IGBP Report 49, Stockholm: 88 pp.
EEA, 1999: Environment in the European Union at the turn of the century. European Environment Agency: 446 pp.
GITAY, H., SUÁREZ, A. & WATSON, R., 2002: Climate change and biodiversity. Technical paper 5, IPCC, 77 pp.
GOTTFRIED, M., PAULI, H., REITER, K. & GRABHERR, G., 1999: A fine-scaled predictive model for changes in species distribution patterns of high mountain plants induced by climate warming. Diversity and Distributions, 5: 241-251.
GOTTFRIED, M., PAULI, H., REITER, K. & GRABHERR, G., 2002: Potential effects of climate change on alpine and nival plants in the Alps. In KÖRNER, C. &SPEHN, E. M. (eds.), Mountain Biodiversity - A Global Assessment. Parthenon Publishing, London, New York: 213-223.
GRABHERR, G., GOTTFRIED, M., GRUBER, A. & PAULI, H., 1995: Patterns and current changes in alpine plant diversity. In CHAPIN III, F. S. & KÖRNER, C. (eds.), Arctic and alpine biodiversity: patterns, causes and ecosystem consequences. Springer, Berlin: 167-181.
GRABHERR, G., GOTTFRIED, M. & PAULI, H., 1994: Climate effects on mountain plants. Nature, 369: 448.
GRABHERR, G., GOTTFRIED, M. & PAULI, H., 2001: Long-term monitoring of mountain peaks in the Alps. In BURGA, C. A., & KRATOCHWIL, A. (ed.), Biomonitoring: General and Applied Aspects on Regional and Global Scales. Tasks for Vegetation Science, Kluwer, Dordrecht: 153-177.
GUISAN, A., THEURILLAT, J.-P. & KIENAST, F., 1998: Predicting the potential distribution of plant species in an alpine environment. Journal of Vegetation Science, 9: 65-74.
HAEBERLI, W., HOELZLE, M. & SUTER, S., 1996: Glacier Mass Balance Bulletin. A contribution to the Global Environment Monitoring System (GEMS) and the International Hydrological Programme. Compiled by the World Glacier Monitoring Service, IAHS (ICSI), UNEP, UNESCO, 4: 88.
HALLOY, S. R. P. & MARK, A. F., 2003: Climate-change effects on alpine plant biodiversity: a New Zealand perspective on quantifying the threat. Arctic, Antarctic, and Alpine Research, 35/2: 248-254.
HARE, W., 2003: Assessment of knowledge on impacts of climate change-contribution to the specification of Art. 2 of the UNFCCC. Background report to the WBGU special report 94.
HEAL, O. W., 1999: Arctic-Alpine Terrestrial Ecosystem Research Initiative (ARTERI) - Final report. A Concerted Action of the European Commission.
HOFER, H. R. 1992: Veränderungen in der Vegetation von 14 Gipfeln des Berninagebietes zwischen 1905 und 1985. Berichte des eobotanischen Institutes ETH, Stiftung Rübel 58: 39-54.
KLANDERUD, K. & BIRKS, H. J. B., 2003: Recent increases in species richness and shifts in altitudinal distributions of Norwegian mountain plants. The Holocene, 13: 1-6.
KÖRNER, C., 1999: Alpine plant life: functional plant ecology of high mountain ecosystems. Springer, Berlin: 338 pp.
KÖRNER, C. & SPEHN, E. M., 2002: Mountain biodiversity: a global assessment. Parthenon Publishing, London, New York.
KULLMAN, L., 2002: Rapid recent range-margin rise of tree and shrub species in the Swedish Scandes. Journal of Ecology, 90: 68-77.
KULLMAN, L., 2003: Recent reversal of Neoglacial climate cooling trend in the Swedish Scandes as evidenced by birch tree-limit rise. Global and Planetary Change, 36: 77-88.
KULLMAN, L., 2004: The changing face of the alpine world. IGBP, Global Change Newsletter 57: 12-14.
MESHINEV, T., APOSTOLOVA, I. & KOLEVA, E., 2000: Influence of warming on timberline rising: a case study on Pinus peuce Griseb. in Bulgaria. Phytocoenologia, 30: 431-438.
MESSERLI, B. & IVES, J. D., 1997: Mountains of the World. The Parthenon Publishing Group, New York: 495 pp.
MOISEEV, P. A. & SHIYATOV, S. G., 2003: Vegetation dynamics at the treeline ecotone in the Ural highlands, Russia. In NAGY, L., GRABHERR, G., KÖRNER, C., & THOMPSON, D.B.A. (ed.), Alpine Biodiversity in Europe - A Europe-wide Assessment of Biological Richness and Change. Ecological studies 167, Springer, Berlin: 423-435.
PAULI, H., GOTTFRIED, M. & GRABHERR, G., 2001: High summits of the Alps in a changing climate. The oldest observation series on high mountain plant diversity in Europe. In WALTHER, G.-R., BURGA, C. A. & EDWARDS, P. J. (eds.), "Fingerprints of Climate Change" - Adapted Behaviour and Shifting Species Ranges. Kluwer Academic Publisher, New York: 139-149.
PAULI, H., GOTTFRIED, M., DIRNBÖCK, T., DULLINGER, S. & GRABHERR, G., 2003: Assessing the long-term dynamics of endemic plants at summit habitats. In NAGY, L., GRABHERR, G., KÖRNER, C. & THOMPSON, D. B. A. (eds.), Alpine Biodiversity in Europe - A Europe-wide Assessment of Biological Richness and Change. Ecological Studies, Springer: 195-207.
PICKERING, C. M. & ARMSTRONG, T., 2003: Potential impact of climate change on plant communities in the Kosciuszko alpine zone. Victorian Naturalist, 120: 263-272.
PRICE, M. F. & NEVILLE, G. R., 2003: Designing strategies to increase the resiliance of alpine/montane systems to climate change. In HANSEN, L., BIRINGER, J. & HOFFMANN, J. (eds.), Buying time: a user's manual for building resistance and resiliance to climate change in natural systems. WWF International, Gland: 73-94.
ROOT, T. L., PRICE, J. T., HALL, K. R., SCHNEIDER, S. H., ROSENZWEIG, C. & POUNDS, A., 2003: Fingerprints of global warming on wild animals and plants. Nature, 421: 57-60.
SAX, D. F. & GAINES, S. D., 2003: Species diversity: from global decreases to local increases. Trends in Ecology & Evolution, 18: 561-566.
STURM, M., RACINE, C. & TAPE, K., 2001: Increasing shrub abundance in the Arctic. Nature, 411: 546-537.
THEURILLAT, J.-P. & GUISAN, A., 2001: Potential impacts of climate change on vegetation in the European Alps: a review. Climatic Change, 50: 77-109.
THOMAS, C. D., CAMERON, A., GREEN, R. E., BAKKENES, M., BEAUMONT, L., COLLINGHAM, Y. C., ERASMUS, B. F. N., FERREIRA DE SIQUEIRA, M., GRAINGER, A., HANNAH, L., HUGHES, L., HUNTLEY, B., VAN JARRSVELD, A. S., MIDGLEY, G. F., MILES, L., ORTEGA-HUERTA, M. A., PETERSON, A. T., PHILLIPS, O. L. & WILLIAMS, S. E., 2004: Extinction risk from climate change. Nature, 427: 145-148.
VÄRE, H., LAMPINEN, R., HUMPHRIES, C. & WILLIAMS, P., 2003: Taxonomic diversity of vascular plants in the European alpine areas. In NAGY, L., GRABHERR, G., KÖRNER, C., & THOMPSON, D.B.A. (ed.), Alpine Biodiversity in Europe - A Europe-wide Assessment of Biological Richness and Change. Springer: 133-148.
WARDLE, D. A., 1999: Biodiversity, ecosystems and interactions that transcend the interface. Trends in Ecology & Evolution, 14: 125-127.
WARDLE, P. & COLEMAN, M. C., 1992: Evidence of rising upper limits of four native New Zealand forest trees. New Zealand Journal of Botany, 30: 303-314.