**4. Threats and opportunities for ground beetles and non-biting midges in relation to climate warming**

Glaciers and permafrost are disappearing all over the world, and with them, we are risking to lose also the associated glacial biodiversity. Therefore, it is mandatory to describe the temporal and spatial biological fingerprint of climate change impacts to deeply understand trends and patterns.

The available literature on ground beetles and non-biting midges is able to give us insights about the threats and opportunities they have in relation to the ongoing climate and, consequently, landscape changes.

### **4.1 Extinction**

*Glaciers and the Polar Environment*

until spring thawing.

**3.6 Non-biting midges in glacier-fed streams**

single Alpine ponds (Agola glacier, 2596 m a.s.l., Brenta Dolomites, Italy), with *M. fuscipes* and *M. eurynotus* as dominant species. The genus is considered semiterrestrial, found in mosses, phytotelmata, springs, ditches, streams and occasionally in the middle of lakes and rock pools [50]. Some ability to survive desiccation and hibernation often in combination with cocoon building and migration of larvae into the sediment [51] has been recorded for several *Metriocnemus* species dwelling in ephemeral habitats that seasonally dry or freeze out. The colonization of these ponds by *Metriocnemus* might be due more to these physiological adaptations than to repeated recolonization as observed for other chironomids colonizing ephemeral ponds [52]. In fact, due to the high geographical isolation of the pond and scarce connectivity with other suitable habitats in the catchment, we can suppose that these species persist by activating a physiological response to physical stress. Most of these species are univoltine, entering diapause in a desiccated-frozen state

Non-biting midges are the main colonizers of glacier-fed streams around the world. Glacially dominated rivers are characterized by a deterministic nature of benthic communities due to the overriding conditions of low water temperature, low channel stability, low food availability and strong daily discharge fluctuations associated to glacier runoff (**Figure 6**). A predictable longitudinal pattern of taxa richness and diversity increasing with distance from the glacier has been described for many European glacier-fed streams, starting from the kryal sector (where maximum water temperature is below 4°C), typically colonized almost exclusively by *Diamesa* species in the temperate regions [53]. *D. steinboecki*, *D. goetghebueri*, *D. tonsa*, *D. zernyi* and *D. bohemani* are the species more frequent and abundant in kryal sites in the Palearctic regions, followed by *D. bertrami*, *D. latitarsis*, *D. modesta*, *D. hamaticornis* and *D. cinerella*. Less frequent are *D. martae*, *D. nowickiana*, *D. longipes*, *D. wuelkeri* and *D. aberrata*; *D. insignipes*, *D. dampfi*, *D. permacra* and

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**Figure 6.**

*northern Pakistan) (photo by L. Latella).*

*Dubani glacial stream at the glacier snout (3232 m a.s.l., 36°N, 74°E; Bagrote Valley, Karakoram range of* 

Currently, no ground beetles living on glacial and periglacial landforms have been declared extinct. On the other hand, the temporal reduction in population size of two high-altitude species (*Nebria germari* and *Trechus dolomitanus*) of the Dolomites (Italy) in 30 years was documented [56]. Specifically, local extinction of *Nebria germari* populations was documented in some high-altitude prairies of the Dolomites, and now the species maintain large populations only on glacial and periglacial landforms; thus, it has become an ice-related species.

As observed for ground beetles, also for non-biting midges from kryal habitats, there is no evidence of global extinction of single species, rather of local extinction caused by the retreat of glaciers. The consequence of the glacial retreat is the further isolation of the populations in the short-term and, in the long-term, their possible disappearance due to very restricted habitat preference and limited dispersal abilities of midges. Glacier shrinking favors an upstream shift of lowland euriecious species of chironomid and other invertebrates, associated with an initial decrease in abundance and finally local extinction of kryal *Diamesa* species and other Diamesinae [57]. *Diamesa longipes* and *Syndiamesa nigra* have not been collected in recent years in Alpine running water [53], and the ice fly *Diamesa steinboecki* has disappeared in some glacier-fed streams in the Southern Alps [58]. The strong cold hardiness of *Diamesa* species [59] and the scarcity of potential refuge areas in glacial and periglacial area threaten these species seriously with extinction. Thus, *Diamesa* species have been suggested to be used as sentinels for climate change, especially in relation to glacier retreat. Recent studies found a direct relationship between the loss of *Diamesa* species in alpine riverine environments and the consequences of the changing climate [58].

### **4.2 Uphill and upstream shift**

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 resulting area reduction of more than 90% from >12 km2 to <1 km2 [60]. The same 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 temporal extent.

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].

#### **4.3 Adaptation**

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 physiological constraints drive species turnover with elevation [65].

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

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outflows.

**4.5 Chemical pollution**

*Glacial Biodiversity: Lessons from Ground-dwelling and Aquatic Insects*

(worms), burrowing and using interstitial habitat. Dietary shifts reflect terrestrial vegetation succession with decreasing glacier cover supplying plant litter to rivers resulting in higher amount of organic material for detritivores. These shifts were observed in glacialized systems in European Alps (Austria and Italy), French Pyrénées, Greenland, Iceland, New Zealand Alps, Norway Western Fjords, US

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

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

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].

*DOI: http://dx.doi.org/10.5772/intechopen.92826*

Rockies, Alaska and Svalbard [67].

populations of cold-adapted species.

**4.4 Refuge areas**

(worms), burrowing and using interstitial habitat. Dietary shifts reflect terrestrial vegetation succession with decreasing glacier cover supplying plant litter to rivers resulting in higher amount of organic material for detritivores. These shifts were observed in glacialized systems in European Alps (Austria and Italy), French Pyrénées, Greenland, Iceland, New Zealand Alps, Norway Western Fjords, US Rockies, Alaska and Svalbard [67].
