Rock Glaciers Help Protect Species in a Warmer Climate

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Grasses and other plant species often thrive on the periphery of major glaciers on active rock periglaciers (Source: Savannah Theilbar).

In a recent study by Duccio Tampucci et al., rock glaciers in the Italian Alps have been shown to host a wide variety of flora and fauna, supporting plant and arthropod species during temporary decadal periods of climatic warming. Certain species that thrive in cold conditions have been prone to high environmental stress during warm climate stages in the past, but given the results of Tampucci’s research, it is now clear that these species may be able to survive in periglacial settings on the edge of existing glaciers.

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One of many species of arthropods equipped to survive in cold temperatures on glacier surfaces. (Source: Rebecca Rendon).

Active rock glaciers, commonly found on the border of larger glaciers and ice sheets, are comprised of coarse debris with intermixed ice or an ice-core. The study has valuable implications on how organisms may respond to changes in temperature, offering a possible explanation for species’ resiliency.

Jonathan Anderson, a retired Glacier National Park ranger, spoke to GlacierHub about the importance of periglacial realms in providing a habitat for animals displaced by modern climate change. “In the years spent in and around the park, it’s clear that more and more animals are feeling the impact of climate change and global warming,” he said. “The areas surrounding the larger glaciers are becoming even more important than before and are now home to many of the species that lived on the receded glacier.”

In their study, Tampucci and team analyzed abiotic dimensions of active rock glaciers such as ground surface temperature, humidity and soil chemistry, as well as biotic factors related to the species abundance of plants and arthropods. This data was then compared to surrounding iceless regions characterized by large scree slopes (small loose stones covering mountain slopes) as an experimental control for the glaciated landforms of interest. Comparisons between these active scree slopes and rock glaciers revealed similar soil geochemistry, yet colder ground surface temperatures existed on the rocky glaciers. Thus, more cold-adapted species existed on rock glaciers.

The Ortles-Cevedale Massif where a large portion of Tampucci et al.’s study took place (Source: Parks.it).
The Ortles-Cevedale Massif where a large portion of Tampucci et al.’s study took place (Source: Parks.it).

The distribution of plant and arthropod species was found to be highly variable, dependent upon soil pH and the severity of mountain slope-instability. This variability is because the fraction of coarse debris and quantity of organic matter changes with the landform’s activity, or amount of mass wasting occurring downslope. The study notes that the heterogeneity in landforms in mountainous regions augments the overall biodiversity of the region.

Anderson affirmed this idea, noting, “The difference in habitats between glaciated terrain and the surrounding, more vegetated regions is crucial for allowing a wide range of animals to coexist.” This variety of landforms contributes to a wide variety of microclimates in which ecologically diverse organisms can reside in close proximity.

Cold-adapted species are likely the first to be affected by region-wide seasonal warming. As temperatures increase, cold-weather habitats are liable to reduce in size and shift to higher altitudinal belts, resulting in species reduction and possible extirpation. Tampucci et al.’s study affirmed the notion that active rock glaciers serve as refugia for cold-adapted species due to the landscape’s microclimate features.

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A view of the shrinking alpine-glacial environment that many species call home (Source: Daniel Rojillo).

The local periglacial environment in the Italian Ortles-Cevedale Massif, for example, was shown to be decoupled from greater regional climate, with sufficient thermal inertia (resistance to temperature change) to support cold-adapted species on a decadal timescale.

Despite the conclusive findings that largely affirm previous assumptions about biodiversity in active rock glaciers, the authors carefully point out that the glacier’s ability to serve as refugia for certain species depends entirely on the length of the warm-climate stage, which can potentially last for millennia. Additionally, the macroclimatic context in which the glaciers reside is important and can influence the landform’s thermal inertia, affecting the temporal scale at which the landscape can shelter cold-climate plants and arthropods.

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The ice crawler Grylloblatta campodeiformis is another example of a cold-adapted arthropod species (Source: Piotr Naskrecki).

The idea that certain periglacial regions may be the saving grace for small plants and animals is encouraging, yet these landforms fail to offer a permanent solution for conservation ecologists. Although active rock glaciers can harbor cold-adapted species for lengths of time, when an organism is forced to depend upon an alpine microclimate, it has become geographically isolated. In this scenario, the degree to which immediately surrounding terrain is inhospitable governs the species’ extinction risk.

“It’s really important to keep in mind that although certain species are adaptable and resilient, every organism has a limit,” Anderson told GlacierHub. “If the local climate continues to warm, these species will likely die in a few generations.” This means that although certain species of arthropods, for example, may be able to survive in undesirably warm conditions, this climatic shift still influences their long-term extinction risk.

While periglacial landforms may play a valuable role in protecting cold-adapted species in temporary periods of climatic warming, a large variety of external factors can influence the length of time an organism may survive in any given microclimate. The understanding that active-rock glaciers can effectively protect a range of plants and arthropods has valuable implications for conservation biologists and biogeographers, offering insight into possible explanations for cold-adapted species resiliency in historical episodes of climatic warming.

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