Contenu du sommaire : La montagne, laboratoire du changement climatique

Alpine ecosystems will be greatly impacted by climatic change, but other factors, such as land use and invasive species, are likely to play an important role too. Climate can influence ecosystems at several levels. We describe some of them, stressing methodological approaches and available data. Climate can modify species phenology, such as flowering date of plants and hatching date in insects. It can also change directly population demography (survival, reproduction, dispersal), and therefore species distribution. Finally it can effect interactions among species –snow cover for example can affect the success of some predators. One characteristic of alpine ecosystems is the presence of snow cover, but surprisingly the role played by snow is relatively poorly known, mainly for logistical reasons. Even if we have made important progress regarding the development of predictive models, particularly so for distribution of alpine plants, we still need to set up observational and experimental networks which properly take into account the variability of alpine ecosystems and of their interactions with climate.

Alpine ecosystems will be greatly impacted by climatic change, but other factors, such as land use and invasive species, are likely to play an important role too. Climate can influence ecosystems at several levels. We describe some of them, stressing methodological approaches and available data. Climate can modify species phenology, such as flowering date of plants and hatching date in insects. It can also change directly population demography (survival, reproduction, dispersal), and therefore species distribution. Finally it can effect interactions among species – snow cover for example can affect the success of some predators. One characteristic of alpine ecosystems is the presence of snow cover, but surprisingly the role played by snow is relatively poorly known, mainly for logistical reasons. Even if we have made important progress regarding the development of predictive models, particularly so for distribution of alpine plants, we still need to set up observational and experimental networks which properly take into account the variability of alpine ecosystems and of their interactions with climate.

Livestock farming systems in the French Alps are particularly exposed to the predicted climate change and most of them have already experienced periods of drought since the beginning of the 2000s. Faced with this risk, livestock farmers have put in place a certain number of measures and envisage introducing others in the future. For the present study, surveys were conducted among livestock farmers to identify these measures and analyses were carried out to characterise the attitudes of livestock farmers to drought conditions and to evaluate changes in the sensitivity of their livestock farming systems. With the exception of those farms with extensive irrigated areas, all the farms are seeking solutions to deal with the risks arising from droughts. One solution is to purchase fodder to compensate for the decrease in the harvests that normally provide animal feed in the winter; the amounts purchased vary with the length of wintering required. For the grazing periods, the high mountain livestock breeders and the dairy systems of the Northern Alps rely above all on extending and over-sizing the pasture areas in relation to the needs of the herds. The livestock farms of the Southern Alps also rely on the diversity of vegetation areas and a certain flexibility in the practices used to adapt to conditions experienced during the year. A succession of dry years could result in more radical breakdowns in the livestock systems. It should also be remembered that climate change is only one of the factors influencing the types of changes taking place on farms.

Livestock farming systems in the French Alps are particularly exposed to the predicted climate change and most of them have already experienced periods of drought since the beginning of the 2000s. Faced with this risk, livestock farmers have put in place a certain number of measures and envisage introducing others in the future. For the present study, surveys were conducted among livestock farmers to identify these measures and analyses were carried out to characterise the attitudes of livestock farmers to drought conditions and to evaluate changes in the sensitivity of their livestock farming systems. With the exception of those farms with extensive irrigated areas, all the farms are seeking solutions to deal with the risks arising from droughts. One solution is to purchase fodder to compensate for the decrease in the harvests that normally provide animal feed in the winter; the amounts purchased vary with the length of wintering required. For the grazing periods, the high mountain livestock breeders and the dairy systems of the Northern Alps rely above all on extending and over-sizing the pasture areas in relation to the needs of the herds. The livestock farms of the Southern Alps also rely on the diversity of vegetation areas and a certain flexibility in the practices used to adapt to conditions experienced during the year. A succession of dry years could result in more radical breakdowns in the livestock systems. It should also be remembered that climate change is only one of the factors influencing the types of changes taking place on farms.

Mountain forests produce a large number of ecosystem services that are going to be affected by climate change. We are expecting an increase in high altitude species that could result in the decrease in resinous and subalpine species. These changes in species could adversely affect biodiversity and timber production. However, we also observe an increase in productivity that favours the production of energy wood and, at least temporarily, timber, as well as carbon storage. Given the possible rise in extreme climatic events, changes in vegetation could be marked by periods of decline, which will be very detrimental to the economic system, protection against natural hazards and biodiversity. Climate change will also have an indirect effect on the forest by increasing the demand for renewable energy and carbon storage. There is a lot of uncertainty about vegetation change predictions and this makes it difficult to define forest management adaptation strategies. Effective crisis management, monitoring of natural transformations of the forest based on the interaction between research and management (adaptive management) and the explicit factoring in of the concept of uncertainty appear to be essential to the maintenance of the ecosystem services provided by the forest.

Mountain forests produce a large number of ecosystem services that are going to be affected by climate change. We are expecting an increase in high altitude species that could result in the decrease in resinous and subalpine species. These changes in species could adversely affect biodiversity and timber production. However, we also observe an increase in productivity that favours the production of energy wood and, at least temporarily, timber, as well as carbon storage. Given the possible rise in extreme climatic events, changes in vegetation could be marked by periods of decline, which will be very detrimental to the economic system, protection against natural hazards and biodiversity. Climate change will also have an indirect effect on the forest by increasing the demand for renewable energy and carbon storage. There is a lot of uncertainty about vegetation change predictions and this makes it difficult to define forest management adaptation strategies. Effective crisis management, monitoring of natural transformations of the forest based on the interaction between research and management (adaptive management) and the explicit factoring in of the concept of uncertainty appear to be essential to the maintenance of the ecosystem services provided by the forest.

Climate change is today a reality at both the international and more local levels. Recent studies have focussed mainly on analysing the consequences of climate change. The present article seeks to examine and qualify the impact of climate change in the mountain areas of the Alps. A first line of enquiry concerns the changing level of danger in the mountain environment. Are mountain areas becoming more dangerous and, if so, in terms of what types of risks and to what degree? However, adopting an approach based on an analysis of natural hazards and their dynamics in response to climate change cannot ignore the economic activities and types of development that already exist in these areas. In this respect, the tourism economy is predominant in mountain regions. Its durability and vitality undoubtedly constitute a priority for local actors. It is not surprising therefore that the latter have set up strategies for adapting to climate change. For planners and decision-makers to ensure integrated approaches in dealing with climate change, it is important that the complex links between natural risks and the types of development in mountain areas are better understood, which calls for a more detailed analysis of the environment in terms of territorial vulnerability.

Climate change is today a reality at both the international and more local levels. Recent studies have focussed mainly on analysing the consequences of climate change. The present article seeks to examine and qualify the impact of climate change in the mountain areas of the Alps. A first line of enquiry concerns the changing level of danger in the mountain environment. Are mountain areas becoming more dangerous and, if so, in terms of what types of risks and to what degree? However, adopting an approach based on an analysis of natural hazards and their dynamics in response to climate change cannot ignore the economic activities and types of development that already exist in these areas. In this respect, the tourism economy is predominant in mountain regions. Its durability and vitality undoubtedly constitute a priority for local actors. It is not surprising therefore that the latter have set up strategies for adapting to climate change. For planners and decision-makers to ensure integrated approaches in dealing with climate change, it is important that the complex links between natural risks and the types of development in mountain areas are better understood, which calls for a more detailed analysis of the environment in terms of territorial vulnerability.