There is growing evidence that biodiversity of cold regions, including high latitude insular systems, will be increasingly threatened by climate change and biological invasions. In this project, we aim to combine existing data with new experiments and observations from cold environments in polar and alpine regions to better understand the synergisms between climate change and biological invasions on species redistributions, to predict how these may change into the future, and to develop mitigation measures to deal with impacts. (a) We will focus on cold environments at high latitudes and elevations (Arctic, sub-Arctic, Antarctic, sub-Antarctic and alpine systems from Austria, Czech Republic, France, Greenland [Denmark], Norway, Switzerland, South Africa, and the UK, in addition to the data we will be able to access via collaborators and/or public databases [MIREN, GMBA, SoilTemp, National botanic conservatories, ect? ), as they are warming at an unprecedented rate and are becoming increasingly vulnerable to invasions under a milder climate. Hence, these environments are excellent sentinels for change, and can act as natural laboratories in which to study the synergisms between, and the combined effects of climate change and biological invasions. (b) We will focus on terrestrial, freshwater and coastal ecosystems/communities/habitats/organisms from cold environments. We will use long-term monitoring data for plants and invertebrates, including georeferenced non-native and native species records (e.g. presence/absence, abundance) collected in surveys spanning a wide range of habitat types, (micro)climatic conditions and elevation gradients. These extensive datasets are already available from members of the proposed consortium, and will be further enriched by new experimental research. If funded, this proposal will lead to the development of new analytical tools and scientific insights, using cutting-edge modelling techniques relying on databases with an unprecedented size and scope to improve our understanding of the dynamics of native and non-native species biogeography in cold environments. Our effort will greatly improve the current knowledge of the mechanisms and factors driving the distribution and assemblages of species at local and regional scales. (c) We will focus on plants and invertebrates whose ecology, fitness and distribution are driven by the microclimatic characteristics of their habitats. Plants and insects are often keystone or pioneer species structuring ecological networks, and especially so in cold environments. Several plants are also ?umbrella? species, for which the long-term conservation will allow protection of their associated habitats and species. By linking the distribution of plants and invertebrates, we will be able to consider and reveal the cascading effects of changes of their ecological interactions.