**4.4 Refuge areas**

*Glaciers and the Polar Environment*

**4.2 Uphill and upstream shift**

temporal extent.

**4.3 Adaptation**

Higher temperatures and increased drought are leading to an upward shift of stenothermal species that depend on low temperatures and therefore to the fragmentation and progressive reduction in their habitat. Any endemic species, like several high-altitude ground beetles, that is restricted to summit areas and has a low dispersion ability is forced to move upward searching for microclimates suitable for its survivor. Data on ground beetles resampled in the same places after decades suggest common trend in cryophilous species. For instance, on the Andes, from 1880 to 1985, the species *Dyscolus diopsis* has shifted approximately 300 m upward, with the

altitudinal shift was observed on the Dolomites for the species *Nebria germari* [27] from 1950 to 2019; the habitat preference for this species was alpine prairies [61], N-exposed scree slopes and recently deglaciated terrains, and currently, it seems to be restricted only to ice-related landforms and scree slopes with high snow cover

Shrinking glaciers are resulting in the lengthening of glacial streams, with consequent upstream migration of specialist species to colonize the "new" stream reach, still harsh, in front of the glacier terminus. Downstream generalist species also migrate upstream, to conquer sites with ameliorated environmental conditions associated to a reduced glacial runoff and increased temperature and channel stability [62, 63]. For example, in the Alps, as first colonizers upstream were observed grazer (chironomid Orthocladiinae among which *Eukiefferiella* spp., *Heleniella* spp., *Orthocladius frigidus* and *Chaetocladius* spp.) and shredder insects (Nemouridae), covering distances from 300 m to about 2 km and a difference in altitude up to 600 m probably favored by higher amount of debris from the banks [58].

To the best of our knowledge, there is no evidence of physiological or morphological adaptation of carabid beetles in relation to the climate change at high altitudes, and it seems that limits to species distributions reflect present environmental tolerance limits rather than simply an historical lack of opportunity for range expansion [64]. Some studies on thermal tolerance highlighted that temperature gradients and acute thermal tolerance do not support the hypothesis that physi-

Cold stenothermal non-biting midges that adapted to live at temperatures close to their physiological limits like *Diamesa* spp. might only survive and reproduce if they can adapt to new environmental conditions or if they are able to avoid the stressor adopting specific behaviors. Barring these abilities, they are expected to disappear. There are evidences of physiological adaptation in Diamesinae to increasing water temperature in glacier-fed streams. For example, *Diamesa zernyi*, *Diamesa tonsa* and *Pseudodiamesa branickii* are cold hardy with a thermal optimum below 6°C but survive short-term heat shock by developing a heat shock response based on the synthesis of heat shock proteins [66]. It is clearly not sufficient to preserve the species considering the observed cases of local extinction. Decreasing glacier cover disadvantages Diamesinae and other cold stenothermal taxa but favors organisms with long life cycles (univoltine) or more (semivoltine) due to continuous growth around the year (life cycle shifts suggest that where glacier cover is high, nondiapausal organisms typically develop rapidly in the spring/summer melt seasons before rivers dry up or freeze through winter) [67]. Furthermore, decreasing glacier cover favors insects that undergo incomplete metamorphosis, such as Plecoptera (stoneflies) and Ephemeroptera (mayflies), and noninsect taxa such as Oligochaeta

ological constraints drive species turnover with elevation [65].

to <1 km2

[60]. The same

resulting area reduction of more than 90% from >12 km2

**154**

If the speed of adaptive capacity—when possible—is not temporally synchronous with the speed of the glacier retreat, the only way to survive for cryophilous species is to find refuge areas. A refuge can be defined as sites able to preserve suitable climate conditions for cold-adapted species in spite of the climate warming [68]. The role of active rock glaciers and debris-covered glaciers as potential warmstage refugia for cold-adapted ground beetle species is supported by data collected on the Italian Alps [16, 28, 40]. The thermal profile observed on some alpine active rock glaciers supports this view indicating decoupling of the local topoclimate from the regional climate, a key factor for a site to serve as a refugium. Specifically, active rock glaciers differ from the surrounding landforms (e.g., scree slopes) by overall lower ground surface temperature (average annual temperatures around or below 0°C). During postglacial periods, cold-adapted species found refuge in cooler habitats, such as subterranean environments (e.g., caves), where they could find cold and stable microclimatic conditions [69]. Thus, we cannot exclude that the same pattern is acting till now for ground beetles on active rock glaciers and debriscovered glaciers, because only these landforms are still able to support large-size populations of cold-adapted species.

In streams, the majority of invertebrates avoid the hazards of freezing or desiccation (due to freezing of the substrate or due to drought caused by increasing temperature) by migrating to unfrozen habitats (e.g., springs fed by groundwater inputs and hyporheic zone), where they remain active [70]. This is a temporary adaptation, to escape daily or seasonal risk of freezing or desiccation. On long time scale, these refugia cannot preserve cold stenothermal *Diamesa steinboecki* and similar species, never found in springs and not confined to the hyporheic having the terrestrial adult. Rock glacier outflows might act as a cold refuge areas after the glacier loss also for aquatic insects due to their constantly cold waters [71]. Ref. [72] investigated five streams fed by rock glaciers in South Tyrol (Italy) and found a dominance of Diamesinae and Orthocladiinae chironomids, besides Plecoptera, Ephemeroptera and Trichoptera (EPT). The authors reported the presence of coldstenothermal species (*Diamesa* spp.), which suggests that rock glacial streams can act as refuge areas after the glacier loss [73]. However, further studies are necessary to demonstrate that cold-hardy *D. steinboecki* and other *Diamesa* species restricted to kryal habitat might survive competition with spring fauna (EPT) in rock glacier outflows.

### **4.5 Chemical pollution**

Among the stressors that threaten the glacial biodiversity, there are also chemicals, i.e., persistent organics pollutants (POPs) deriving from long-range atmospheric transport and pesticides and emerging contaminants (e.g., personal care products as fragrances and polybrominated diphenyl ethers (PBDEs) widely used as flame retardants) carried to the glaciers by short-medium range atmospheric transport. These pollutants undergo cold condensation and accumulate in the glacier ice until their release in melt waters and ice-free soil [74, 75].

Among organic contaminants detected in glacier-fed streams, attention was paid to the insecticide chlorpyrifos, since high toxicity to insects and peak release by glacier melting occur concurrently with the period in which the streams are more densely populated by macroinvertebrates [76]. Chlorpyrifos and other organophosphate insecticides are known to exhibit increased toxicity in invertebrates at elevated temperatures [77]. Specifically, warming influences chlorpyrifos uptake in aquatic insects magnifying its negative effect on fauna. Other contaminants are heavy metals released by remains of the Great War, such as bombs, bullets, cannon parts and barbed wire buried in the ice 100 years ago, that are emerging due to glaciers retreating. These new sources of contamination have been recently documented for ice melt waters in the Italian Alps (mainly by nickel, arsenic and lead, unpublished data). Contamination of soils of the 1914–1918 Western Front zone, in Belgium and France by copper, lead and zinc was previously detected by [78]. Pesticides, fragrances and heavy metals affect swimming behavior and metabolism of *Diamesa* species from glacier-fed streams [79] at trace concentration (in order of ng/L), with still unknown effects on aquatic food web and on terrestrial fauna (*via* food web). To our knowledge, the understanding of final environmental fate of such pollutants is still scarce and fragmentary. Recently, evidences of microplastic bioaccumulation are given for freshwater amphipods from Svalbard glacier-fed streams [80] and for *Diamesa zernyi* larvae from the Amola Glacier-fed stream (Italy). No information is now available on their effects on ground beetle fauna.
