Réf. Beniston 2003 - A

Référence bibliographique complète
BENISTON,M. Climatic change in mountain regions: A review of possible impacts. Climatic Change, 2003, Volume 59, p5-31.

Abstract: This paper addresses a number of issues related to current and future climatic change and its impacts on mountain environments and economies, focusing on the ‘Mountain Regions’ Chapter 13 of Agenda 21, a basis document presented at the 1992 United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro, and the International Year of the Mountains (IYM) 2002. The awareness that mountain regions are an important component of the earth’s ecosystems, in terms of the resources and services that they provide to both mountain communities and lowland residents, has risen in the intervening decade. Based upon the themes outlined in the supporting documents for IYM, this paper will provide a succinct review of a number of sectors that warrant particular attention, according to IYM. These sectors include water resources, ecosystems and biological diversity, natural hazards, health issues, and tourism. A portfolio of research and policy options are discussed in the concluding section, as a summary of what the IYM and other concerned international networks consider to be the priority for mountain environmental protection, capacity building, and response strategies in the face of climatic change in the short to medium term future.

Mots-clés
Mountains, climate change, overview of impacts

Organismes / Contacts
Department of Geosciences, University of Fribourg. Martin.Beniston@unige.ch

(1) - Paramètre(s) atmosphérique(s) modifié(s)
(2) - Elément(s) du milieu impacté(s)
(3) - Type(s) d'aléa impacté(s)
(3) - Sous-type(s) d'aléa
Precipitation, temperature River runoff, snow cover, vegetation    

Pays / Zone
Massif / Secteur
Site(s) d'étude
Exposition
Altitude
Période(s) d'observation
Mountain Regions in the Wolrd          

(1) - Modifications des paramètres atmosphériques
Reconstitutions
 
Observations
 
Modélisations
Projections of changes in the precipitation patterns in mountain are tenuous in most General Circulation Models because mountain toporaphy is poorly resolved and, as a result, the controls of topography on precipitation are not adequatly represented. It has also been recoginized that there are superimposed effects of natural modes o climate variability such as El Nino/ENSO, NAO... ...can perturb mean precipitation patterns on time scales ranging from seasons to decades. Such mechanisms are not well predicted by climate models.
Hypothèses


Informations complémentaires (données utilisées, méthode, scénarios, etc.)

 


(2) - Impacts du changement climatique sur le milieu naturel
Reconstitutions
 
Observations
 
Modélisations
 
Hypothèses
Because temperature decreases with altitude by 5–10 ◦C/km, a first-order approximation regarding the response of vegetation to climate change is that species will migrate upwards to find climatic conditions in tomorrow’s climate which are similar to today’s (e.g., McArthur, 1972; Peters and Darling, 1985). According to this paradigm, the expected impacts of climate change in mountainous nature reserves would include the loss of the coolest climatic zones at the peaks of the mountains and the linear shift of all remaining vegetation belts upslope. Because mountain tops are smaller than bases, the present belts at high elevations would occupy smaller and smaller areas, and the corresponding species would have reductions in population and may thus become more vulnerable to genetic and environmental pressure (Peters and Darling, 1985; Hansen-Bristow et al., 1988; Bortenschlager, 1993). However, the migration hypothesis may not always be applicable because of the different climatic tolerance of species involved, including genetic variability between species, different longevities and survival rates, and the competition by invading species (Dukes and Mooney, 1999). Adaptation pathways in the face of changing environmental conditions include the progressive replacement of the currently dominant species by a more thermophilous (heat-loving) species. It is expected that, on a general level, the response of ecosystems in mountain regions will be most important at ecoclines (the ecosystem boundaries if these are gradual), or ecotones (where step-like changes in vegetation types occur). Those that reproduce slowly and disperse poorly, and those which are isolated or are highly specialized, will therefore be highly sensitive to seemingly minor stresses.

The hydrological cycle will be enhanced under warmer changing climatic conditions, the current distribution, seasonality, and amount of precipitation may undergo significant changes in various regions. The consequences for river runoff are likely to affect not only the watersheds within the mountains themselves,but also in the lowland regions that are heavily dependent on this mountain ressoures.

For every 1°C increase in temperature, the snowline will rise by about 150 m. Shifts in snow-pack duration and amount as a consequence of sustained changes in climate will be crucial factors in water avaibility for hydrological basins.

Sensibilité du milieu à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
   

(3) - Impacts du changement climatique sur l'aléa
Reconstitutions
 
Observations
 
Modélisations
 
Hypothèses
 

Paramètre de l'aléa
Sensibilité du paramètres de l'aléa à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
 
 

(5) - Syntèses et préconisations
For assessing current and future trends in regional climate, the current spatial resolution of General Circulation Models (GCM) is generally too crude to adequately represent the orographic detail of most mountain regions. On the other hand, most impacts research requires information with fine spatial definition, where the regional detail of topography or land-cover are important determinants in the response of natural and managed systems to change.

Références citées :

BORTENSCHLAGER, S. 1993, ‘Das höchst gelegene Moor der Ostalpen “Moor am Rofenberg” 2760 m.’, Festschrift Zoller, Diss. Bot. vol 196, p329–334.

DUKES, J. S. and MOONEY, H. A.: 1999, ‘Does Global Change Increase the Success of Biological Invaders?’, Trends in Ecology and Evolution 14, p135–139.

HANSEN-BRISTOW, K. J., IVES, J. D., and WILSON, J. P.: 1988, ‘Climatic Variability and Tree Response within the Forest-Alpine Tundra Ecotone’, Annals of the Association of American Geographers, vol 78, p505–519.

McARTHUR, R. H.: 1972, Geographical Ecology, Harper and Row, New York.

PETERS, R. L. and DARLING, J. D. S.: 1985, ‘The Greenhouse Effect and Nature Reserves: Global WarmingWould Diminish Biological Diversity by Causing Extinctions among Reserve Species’, Bioscience 35, p 707–717.