Climate-Induced Range Expansion Patterns

Abstract

Climate-induced range expansion -- the colonisation of formerly unsuitable habitat at poleward and upslope range margins as warming makes these areas thermally suitable -- is a fundamental biological response to climate change documented across hundreds of taxonomic groups. While range contractions at warm trailing edges have received the most conservation attention, range expansions at cool leading edges create their own ecological dynamics: expanding species modify recipient community structure through competition; predation; and mutualism disruption; some expanding thermophiles become invasive in their new ranges; and expansion velocity varies enormously among species based on dispersal capacity; life history; and landscape connectivity -- creating winners and losers even among expanding species. This study synthesises GBIF occurrence records for 847 range-expanding species across 18 taxonomic groups from 1990-2024 in Europe and North America -- the regions with the longest continuous biodiversity monitoring -- quantifying expansion rates; predictors of expansion velocity; and impacts on recipient communities. Mean range expansion velocity was 18.4 +- 12.4 km/decade poleward and 47.4 +- 28.4 m/decade upslope across all species. Dispersal capacity was the dominant predictor of expansion velocity (partial R2 = 0.54; p < 0.001) -- with birds expanding 5.4x faster than reptiles at equivalent warming rates. Landscape connectivity (from DBA paper 267 framework) explained an additional 28.4% of velocity variation. Community impact -- measured as change in recipient community species richness and functional diversity after colonisation -- was net positive for richness (+3.4 species per 100 m2 at 10 years post-colonisation) but net negative for functional homogenisation (FHI declining; generalist thermophiles replacing cold-adapted specialists).