The Biodiversity of Retreating Glaciers Leaves an Ecological Legacy in Emerging Soil Communities

ABSTRACT

Glacier retreat is transforming high‐mountain and polar landscapes, replacing ice with vast, newly exposed terrains where soil development and ecological succession start. Although ecosystems developing in deglaciated terrains are often viewed as starting from scratch, glaciers host diverse communities whose links with emerging soils remain unquantified. Using environmental DNA metabarcoding, we provide the first multi‐taxa assessment of biodiversity transitions across the supraglacial–proglacial interface across five glacier systems in Svalbard, the Alps and Patagonia. We analysed 212 samples from the surfaces of retreating glaciers and their forelands, spanning a chronosequence from 1 to 483 years since deglaciation. Recently deglaciated soils (≤ 10 years since glacier retreat) showed taxonomic and functional similarity to supraglacial communities. This ecological continuity was highly taxon‐specific, being pronounced for communities of microorganisms (Bacteria, Fungi, Protista) but weak for animals (e.g., Collembola, Insecta). For microbes, similarity diminished rapidly over succession as community turnover increased, and functional composition shifted from phototrophic and saprotrophic dominance toward heterotrophic and symbiotic assemblages. Shared microbial taxa and functions indicate a transient glacial influence during early soil succession. Our results suggest that early soil communities are not assembled independently of glacier ecosystems, but are initially linked to them through diverse ecological pathways that diminish over time. The observed glacier–proglacial connectivity challenges the view of succession on deglaciated terrains as beginning on lifeless substrates and instead points to a glacial legacy in emerging soils. As glaciers rapidly disappear under climate change, the unique biodiversity they host is also being lost, underscoring the urgent need to study supraglacial and proglacial systems together. Such integration is essential to understand ecological succession in proglacial ecosystems, which are expected to play an increasingly important role in this century.