The global diversity and decline of glacier animals

Glacier environments host an unrecognized number of animals that are at high risk of extinction due to global warming. Yet, the absence of comprehensive analyses has hampered the development of a coordinated agenda for research and conservation. By assembling a global dataset of terrestrial and freshwater animals in glacial habitats, we show that glacier environments host at least 152 animal species from 14 classes and 7 phyla. This diversity is underestimated for nearly all the groups and we detected widespread taxonomical, ecological, and geographical biases. Glacier animals exhibited diverse ecological patterns, with 73 species reported exclusively from glacial habitats (glacier specialists). Biogeographical patterns showed clear differences between groups, with some taxa (tardigrades, rotifers) found mostly in polar areas and others (insects, springtails) associated with tropical and temperate mountains. Glacier regions with a lower temperature showed a higher richness of glacier specialists. Glacier animals were widespread across the metazoan tree of life; the ability to disperse passively by wind emerged as the strongest driver of the occurrence of glacier animals. By linking the distribution of glacier specialists to scenarios of glacier retreat, we identified areas and species that are likely to experience abrupt declines in the next few decades, as well as species that could face complete habitat loss. Our results call for urgent actions to secure the future of glacier environments and their singular, understudied fauna.