Why do the Alps and the Arctic share similar plants and animals?

The similarities between the flora and fauna of high mountain ranges, such as the Alps, and the Arctic are primarily the result of historical climate shifts during the Ice Ages of the last two million years.1

During these glacial intervals, cold-adapted species expanded their ranges far beyond the ice sheets that covered much of northern North America, Europe, and Asia. As the climate later warmed, these organisms were forced to retreat to environments that could sustain their cold-adapted needs. This led to two primary migration patterns: populations moved northward toward Arctic latitudes or migrated to higher elevations in mountainous terrain, where cooler temperatures mimicked their previous habitats.1

Because these mountain summits act as isolated "islands" of cool climate, they have served as refuges for these species. This shared history of migration and environmental adaptation explains why many plants and animals found in the Arctic are also present in high-altitude mountain ecosystems.1