The Arctic and parts of Antarctica are experiencing very rapid climate and environmental changes. Earth system models further predict increasing temperatures and changing precipitation patterns during the 21^st century in these polar regions. It can be expected that these changes will affect the biodiversity and functioning of polar terrestrial ecosystems, yet the resilience of these habitats and their vulnerability to change is largely unknown due to the lack of long-term monitoring data and extensive field experiments. The aim of this project is to study the biodiversity and genetic functional potential of microbial communities in polar desert and tundra soils in the Arctic and Antarctica, and to consolidate long-term monitoring and field-based experiments to assess the response of the ecosystems to climate change. To achieve this, field based research will be combined with laboratory experiments and analyses.