Upward Shifts of Species Range in mediterranean High-Mountain forests Under Current Climate change: A Review

ABSTRACT:Anthropogenic global warming represents a serious threat to mountain forest ecosystems. For more than two decades studies have increasingly reported altitudinal range shifts in tree species in response to climate change. This paper is primarily addressed to ecologists with limited background on this topic and presents a review of the main studies investigating the impact of global warming on the upward migration of trees in high-mountain forests around the Mediterranean Basin. Various scientific databases were consulted, covering published literature between 2000 and 2021 that clearly indicate an upward shift of the main Mediterranean tree species (e.g. Pinus, Quercus, Abies and Fagus). From these studies, we retrieved 1) the status of the upward shift of tree species; 2) the main drivers of this shift; and 3) the most common assessment methods used. The results indicated that several tree species in the Mediterranean Basin are experiencing expansion and/or retraction at leading- and/or trailing-edges, respectively, although some are showing opposite movements or no changes. Climate warming and land-use changes are considered the main drivers of species range shifts. These shifts are frequently assessed through monitoring tree line changes along elevational gradients. Despite the considerable advances in these studies, there are large gaps for some Mediterranean tree species, which need particular attention.