Réf. Bader et Kunz 2000c - R: PNR 31

Référence bibliographique complète
Climate Risks - The Challenge for Alpine Region - PNR31. / ed. by BADER S., KUNZ P. Zürich : vdf Hochschuverlag AG an der ETH Zürich, 2000, 291 p.

Mots-clés
Forest fires, meteorological parameters, climate change.

Organismes / Contact
Partenaires
NRP 31 Programme Leaders
Thunstrasse 91, CH-3006 Berne
Tel. : +41 31 356 65 65
Fonds National Suisse; Swiss Re; Office Fédéral de l'Environnement, des Forêts et du Paysage; Direction du Développement et de la Coopération; ProClim; CLIRIS Recherche sur les Risques Climatiques; Hochschulverlag an der ETH Zürich

Principaux rapports scientifiques sur lesquels s'est appuyé le rapport
"Incendi boschivi al Sud delle Alpi: passato, presente e possibli sviluppi futuri", Conedera, Marcozzi et al, 1996.

(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
  Forest and vegetation Forest fires  

Pays / Zone
Massif / Secteur
Site(s) d'étude
Exposition
Altitude
Période(s) d'observation
Switzerland Southern Alps Ticino canton, southern valleys of Graubünden and the Zwischbergental-Gondo-Simplon region in Valais canton.     1900-1994

(1) - Modifications des paramètres atmosphériques
Reconstitutions
 
Observations
 
Modélisations
 
Hypothèses
 

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

(2) - Effets du changement climatique sur le milieu naturel
Reconstitutions
 
Observations
 
Modélisations
 
Hypothèses
 

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

(2) - Effets du changement climatique sur le milieu naturel
Reconstitutions
 
Observations
According to the inventory the overall number of fire events was constant from 1900 to 1960, fluctuating around 30 events/year. The fequency of fire has increased, levelling out now at about 90 cases/year. This development must be related to the rapid changes in socio-economic conditions in the southern Alps since the 1960s.
Modélisations
Simulations have demonstrated the significant effect of meteorological factors on the occurence of forest fires. These factors are: temperature and relative air humidity, periods of drought, prolonged high pressure situations (blocking highs), thunderstorms with lightning, days of föhn wind and the maximum speed of this wind. The short-term, daily weather conditions are the more decisive ones. Since 1951 there is a weak correlation between the increasing frequency of fires and the decrease in precipitation. The correlation is clearer when viewed on a seasonal basis, for example in summer.
Hypothèses
The study of forest fires during past decades suggests that future developments will include:
an increase in the number of forest fires during the summer half of the year (thunderstorms), particulary at high altitudes now that the timber line is rising;
a geater fire hazard owing to the future type of vegetation which will develop, particulary at low altitudes (warmth-loving species);
the natural plant succession following a fire, which will comprise fewer species. This will be found mainly in low-altitude areas.

The effects of atmospheric warming should not be neglected: vegetation zones will migrate to higher altitudes, with warmth-loving plant species such as laurels becoming established. Fires will then be an essential ecological component in the natural control of biomass and in the development of forest ecosystems, particularly in areas not exploited commercially. The effects of climate change will merely worsen an already unfavorable situation.

Paramètre de l'aléa
Sensibilité du paramètres de l'aléa à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
Forest fire occurence
Temperature and relative air humidity, periods of drought, prolonged high pressure situations, thunderstorms with lightning, days of föhn wind and the maximum speed of this wind.
5300 events have been recorded between 1900 and 1994 on the basis of the reports submitted by the forestry service and fire brigade. It covers the whole Ticino canton, the southern valleys of Graubünden and the Zwischbergental-Gondo-Simplon region in Valais canton.
The links between forest fires and weather conditions have been analysed in 2 ways: firstly by considering how the frequency of events relates to the main meteorological parameters, and secondly by using a statistical model to establish how the fire situation is affected by variables such as the seasons, the phyto-climatic regions to the south of the Alps, anthropogenic influences, and other meteorological parameters of particular short-term significance.

(4) - Remarques générales
The decisive factor fot the future pattern of forest fires will be the way in which the land is managed. The crucial anthropogenic aspects will be soil management, environmental education and legislation. These may well mask the natural factors.

(5) - Préconisations et recomandations
Destinataires et portée du rapport Policy makers, swiss citizens, teachers and students in the climatic and environmental studies
Types de recommandations et / ou préconisations