Influences of large-scale climatic variability on reindeer population dynamics: implications for reindeer husbandry in Norway

There is increasing evidence that the globe is currently warming, with changes being more pronounced in northern latitudes. Understanding the ecological effects of climatic variability is therefore important. There is recent support for the idea that a large-scale atmospheric phenomenon, the North Atlantic Oscillation (NAO), through its effects on vegetation and regional weather conditions, influences several aspects of life histories and population dynamic processes of several mammal species, including reindeer Rangifer tarandus. However, patterns are inconsistent both between species and within species. Here, we focus on reindeer, a herbivore that inhabits an extremely seasonal environment. We review and discuss predicted patterns of global climatic change in Norway and assess potential consequences for reindeer husbandry. We argue that although it is clearly shown that local and global climate affect reindeer directly (e.g. increased energetic costs of moving through deep snow and in accessing forage through snow) and indirectly (e.g. effect on forage plant biomass and quality, level of insect harassment and associated parasitism), it is difficult to predict a general pattern of how future climate change will influence this species. It is especially difficult to predict how reindeer husbandry (an important economic and cultural activity for the Saami People) will be affected in Norway. Indeed, (1) patterns in life history traits and population parameters of reindeer vary over space and time, (2) both temperature and precipitation will increase in Norway, with greater changes in the North, i.e. the areas with reindeer husbandry, but the rate of increase will vary with space and seasons, (3) there are several indirect effects of global warming that can complicate the ecological response, especially involving the response of vegetation (e.g. forage on which reindeer depend), and (4) spatial variation, seasonality, complexity of the ecosystem functioning and nonlinearity of ecological processes make any firm prediction uncertain. Consequently, it is difficult to assess the practical and socio-economic implications for the reindeer husbandry industry.