Vegetation Islands on Continents and the Impact of Climate Change—Case Study of the Alpine-Subalpine Belt of the Romanian Carpathians, and a Flagship Species Carex curvula

Abstract

Alpine and subalpine belts on continental Europe can be viewed as “islands” of cold-adapted vegetation surrounded by a “sea” of thermophilic species. Carex curvula , a flagship species that dominates high-elevation grasslands, provides an ideal case study for understanding the broader impacts of climate change on these alpine “vegetation islands”. We built species distribution models for Carex curvula using the biomod2 package in R, testing multiple modeling techniques (Random Forest, Boosted Regression Trees, XGBoost, etc.) with two uncorrelated climatic variables (mean temperature of the coldest quarter and precipitation of the driest month). Model performance, evaluated via ROC (AUC), showed Random Forest as the best algorithm. Future simulations, based on CMIP6 global circulation models (MRI-ESM2-0, UKESM1.0-LL) and mid-range (ssp245) versus high (ssp585) emissions scenarios for 2041-2060 and 2061-2080, consistently forecast significant reductions (10% - 45% to 35% - 80% lost) in climatically suitable areas for Carex curvula . High-elevation habitats in the Romanian Carpathians and the Alps remain potential strongholds, although intensifying competition from thermophilic species may further challenge Carex curvula ’s persistence. These findings highlight the vulnerability of alpine “vegetation islands” to climate change and reinforce the value of Carex curvula as a model organism for projecting broader ecological shifts in Europe’s high-altitude environments.