It is a place where the conditions typical of the Arctic Ocean region meet a more southern and continental clime – it takes particular skill to predict weather in this area. The terrain in the Käsivarsi Wilderness Area rises high above sea level and the landscape is dominated by high fells, including Saana (1,029 m), Termisvaara (1,024 m) and Halti (1,328 m).
The Käsivarsi Wilderness Area is home to many northern species that require a very specific habitat, including the Norwegian lemming, gyrfalcon, snowy owl and, occasionally, even the arctic fox. Relatively few animals live here because the cold and austere environment offers meagre living conditions. However, peaks in lemming and other small rodent populations form an exception to the rule.
The size of animal and plant populations varies greatly from one year to the other. Small mammal populations (Norwegian lemmings and other voles) peak every four to five years. Predator populations, including fox, ermine, rough-legged buzzard, short-eared owl and long-tailed skua populations, then peak in response. The mountain birch forests surrounding the village of Kilpisjärvi are home to more bluethroats than can be found in any other location around the world. They may also harbour mountain hares or grey-sided voles. Salmonoids that are highly selective of their habitat, like the arctic char, brown trout and whitefish, thrive in the oxygen-rich waters of the fells. The highest fells in the area are home to many butterfly species that in their juvenile forms eat specific mountain plants only. The mosquito season begins around midsummer.
List of species: Vertebrates of Northwestern Lapland (Antero Järvinen and Arto Muinonen)
Winter persists nearly all year long in the Kilpisjärvi area. The general growing season only lasts for 100 days. Lake Kilpisjärvi does not clear of ice until around midsummer. In spite of all this, the area has abundant vegetation. Mountain birch forests may be found as high as 600 metres above sea level, where they give way to a barer terrain of dwarf birch and many other plants as well as mosses and lichen. Of all Finnish flowering plants, the glacier buttercup can survive the highest altitude. However, glacier buttercup populations have dramatically decreased over the past few decades.
Because the highest fells near Kilpisjärvi are over 400 metres in height, the vegetation in the area is diverse and distinctive. Due to the limestone in the soil, Kilpisjärvi is home to many plants and mosses that specifically require calcareous soil. Located only 40 kilometres from the Arctic Sea, Kilpisjärvi has many maritime plant species which are otherwise rare in Finland.
The area around Lake Kilpisjärvi is unique from a geological perspective. Here ancient Finnish bedrock, over 2.8 billion years old, encounters the relatively young Scandinavian Mountains, aged only 400 to 600 million years. The young bedrock contains crumbly calcareous dolomite. The most common rock type in the area is granodiorite, in addition to which the bedrock also contains plenty of granite and granite-gneiss.
The landscape is dominated by the Saana, Termisvaara and Halti fells, all over a kilometre in height and created during the folding of the Scandinavian Mountains. Later transitions, uplifts and erosion in the land have further increased the relative altitudes. The highest point of Finland is located in this area, on the slope of one of the sub-summits of Halti, known as Haldičohkka.
Kilpisjärvi has a distinctly oceanic climate affected by its northern location and altitude: the area is located over 400 metres above sea level and less than 50 kilometres from the Arctic Ocean. The climate is very arctic with one of the lowest mean annual temperatures on the European continent at only 2.3 °C. On average, the temperature does not rise above +10.9 °C in July. The ground is usually covered in snow from September or October to early June. Patches of snow may be found on the slopes of Malla all year round.