In Ukraine during 2008–2010, the first SDM matched the red squirrel (S. vulgaris) based on GLM-by-2050, and which covered Eastern Europe, was developed and used by the Land and Resource Management Center (ULRMC, Kyiv). Our new study reveals further development of the analysis by using relevant IPCC climate change scenarios. We took into account materials on S. vulgaris (and S. anomalus) distribution, as well as selected associated species, and the WorldClim with respective maps and current bioclimatic variables, and its projections for four relevant scenarios which combined SSPs & RCPs by 2100. The simulations of scenario SSP1 & RCP2.6 associated with an average temperature increase of 1.5 °C show that climate change could cause the loss of 12 % of suitable habitats of the species in Eastern Europe and 49 % in Ukraine. The simulations for SSP2 & RCP4.5 (with average temperature increase of 1.8 °C) demonstrates, respectively, a potential loss of 14 % and 57 % of suitable habitats. Simulations of SSP3 & RCP7.0 and SSP5 & RCP8.5 scenario (with average temperature increase of >> 2 °C) shows a loss of 30 % and 41 % of suitable habitats within Eastern Europe, and more than 90 % in Ukraine. Since each percent of such changes provokes enormous losses in ecosystems and biodiversity, we emphasize the current need for countries to aim and achieve the most ambitious climate change commitments to stabilize the increase of temperature, i.e. within 1.5 °C. Our comparison platform included also SDMs of some trees (oak, beech, spruce, pine, linden, and birch — Quercus robur, Fagus sylvatica, Picea abies, Pinus silvestris, Tilia cordata, Betula spp.), as well as SDM for the marten (Martes martes), for all of which we had already developed GLM-by-2050. Consequently, the new projections demonstrated that all habitats of the red squirrel and associated species are expected to shift mostly ‘to the north’ by 2100, and their localities in the Caucasus Mountain areas might be fragmented. Most likely, in nature, this complicated displacement revealed by the mentioned modelling will happen not in the form of direct migration of individuals ‘to the north’, but through active synanthropization of the red squirrel. How durable and satisfactory this mechanism is for natural selection remains a mystery. The territories from which S. v. ukrainicus (Mygulin, 1928) historically originated and was described have changed significantly: the respective landscape ecosystem losses have reached up to 50 % and more. By 2100, significant habitat changes are likely to be also demonstrated by beech and birch. This research can be used by educators in teaching the history of science, applied ecology, nature conservation, and geoinformatics in biology. This research is dedicated to the Squirrel Year 2020.
Key words: red squirrel, Sciurus vulgaris, SDM, WorldClim, SSP, RCP, Ukraine, Eastern Europe.