Abstract
The semi-domesticated reindeer (Rangifer tarandus L.) is a natural and cultural resource for Saami herders. The pastoral activity in Swedish Lapland is traditionally semi-nomadic, and takes place between the summer mountain pastures and boreal forest landscape in winter. This breeding system is increasingly threatened by climate change, altering the accessibility and availability of plant resources and disrupting seasonal migration and demography of semi-domesticated reindeer. This study is focussed on the effect of climate time scales on ecological habitats and on the annual demography of reindeer herds. Two types of time slicing are compared: the four season’s weather used in climatology, and the pastoral seasons used by Saami reindeer herders (Saami Parliement). Meanwhile, the advantages of local climatic variables are compared to regional atmospheric indices, in an effort to determine of the impact of climate variability on the demography of reindeer. The study focus on the 1999-2013 period, in regards to the availability of sources, and because it is later to a statistical breakdown of regional and local weather types observed in 1988 (1950-2013). First, we characterize the temporal variability of land surface temperatures (MODIS) for different ecological habitats of the North Bothnia region (Sweden, CLC 2006). Time slicing in pastoral seasons better reflects the irregularity of land surface temperatures of the Rangifer tarandus L.’s ecological habitats, than the four weather seasons. Correlation tests are then performed (Spearman type) between regional atmospheric indices (NOAA-NCEP), local climatology (Abisko station, NOAA-NCDC, 1998-2013) and annual headcounts of two large herds of Norrbotten County, distinguishing fawns, male and female (1999-2013, Saami Parliement). Climatic conditions of late summer, the pastoral season being to a period of rest and regeneration of the ungulate species, correlate with reindeer population the best; they are indeed crucial to the ungulate species to capitalize energy resources for its survival and reproduction (“capital-breeder”). Atmospheric variables are more frequently and better correlated with the demography of reindeer compared to climatic variables. The number of killed reindeer is correlated with annual headcounts, but it also depends from the subsidized price of the meat. The Saami pastoral calendar allows a clear view of the climatic irregularity and of its impact on the demography of reindeer. The effects of climate irregularity is shown more clearly when using synthetic variables on a regional scale than local variables.