Climate tracking by alpine insect distribution across a century:
concentric retreats, small refugia and strong elevational shifts in
bumblebees
Abstract
Cold-adapted species endangered by global change are crucial cases for
understanding range dynamics and its interface with conservation. In
view of climate change and their sensitivity, Alpine insects should
modify their distribution by reducing ranges, while being unable of
sufficient displacements and mostly moving uphill. To test these
hypotheses, we targeted four threatened, high-altitude bumblebees
differing in subgenera and elevation ranges, and covering the main
central and south European mountains. We performed species distribution
models including climate and habitat, and we described elevation uphill
and the year of change with broken-line regressions. Results indicate
that climate change will cause severe future range contractions across
large areas, more in the Apennines (80% - 85% ca) than the Alps and
Pyrenees (24 - 56% ca), with mostly concentric retreats as future
extents will nearly entirely be included in the present ones.
Remarkably, since the ‘80s elevation uplift has started by about 325 -
535 m, a period coinciding with the beginning of the main warming, and
will continue. The size and distribution of climate refugia will
challenge conservation: they will be small and context specific (2-60%
of current areas), but while in the Apennines and Pyrenees they will be
nearly entirely within Protected Areas, only a third will be so for the
Alps. Such impressive distribution changes demonstrates that
cold-adapted bumblebees can accurately track climate change and be
precise sentinels of it, and these results link with the investigated
species being specialists with specific habitat requirements of
temperature and glacier presence. Overall, the distribution of cold
specialist bumblebees driven by climate change demonstrates that
conservation should act upon the dynamic realities of species ranges
because their range reduction, the impossibility of finding new areas
and the movement uphill emerge as consistent patterns.