Where Can Alpine Plants Hide from Global Warming?

Androsace alpine living on rock glaciers as well as moraine ridges and deglaciated forelands (Source: Apollonio Tottoli/Flickr).

Environmental conditions, including climate, strongly influence the distribution of plant species. As temperatures continue to rise around the world, many people are concerned about the possible shifts in distribution of plant species, since plants are immobile, and many of them have a limited ability to disperse. These restrictions to changes in their distribution are particularly severe for plants that are adapted to cold conditions, such as those found in high mountain regions.

Studies by Valenti Rull and others have shown that during interglacial periods in the geological past, alpine plants were able to disperse to microrefugia, small-scale sites which allowed species to persist when most of their ranges became unsuitable for them. Thus, in the current era of warming, such sites, with locally favorable climate, could once again prove to be important for the survival of cold-adapted alpine species. A newly published study by Rodolfo Gentili of the Department of Environmental Sciences at the University of Milan and several co-authors in Ecological Complexity establishes a fresh approach to the study  of microrefugia. The authors examined the geomorphological and ecological features of microrefugia during earlier interglacial stages and used these features to identify potential microrefugia areas for alpine plants in and near glaciers, in both the present and the near future.

Leucanthemopsis alpine living on mountain summits (Source: Apollonio Tottoli)
Leucanthemopsis alpine living on mountain summits (Source: Apollonio Tottoli/Flickr).

In general, there are three recognized strategies which alpine plants can adapt to survive under a warming climate. They can migrate to higher elevation, remain at local microrefugia or evolve through genetic differentiation to adapt to new climate. However, there had been no overview to date of how plants in the Alps and other high mountains of Europe could respond to future warming. Gentili and his co-authors conducted  a thorough literature review, focusing in particular on geomorphological processes and landforms associated with plant communities in alpine environment. (They found only one study which addressed the genetic evolution of an alpine plant.)

The authors developed a typology of alpine landforms and characterized each one according to its “vegetation features, climatic controls, microclimate features of active landforms and microrefugium functions.” They recognized eight landform types, which differ in terms of the processes that generate them. These landforms are mountain summits, debris-covered glaciers, moraine ridges and deglaciated forelands, nivation niches or snow patches,rock glaciers, alpine composite debris cones (debris slopes and scree), alpine corridors (composite channels, including avalanche channels and tracks), and ice caves.

Saxifraga oppositifolia living on alpine corridors (Source: Alastair Rae/Flickr).
Saxifraga oppositifolia living on alpine corridors (Source: Alastair Rae/Flickr).

Taken individually, all of these eight landforms have been documented in the published literature as serving currently as microrefugia, except for the debris-covered glaciers, which nonetheless are promising as future microrefugia because of their relatively cool temperatures which result from the presence of sub-surface ice. The other landforms all have been shown to function as microrefugia. They offer a number of advantages, including suitable sites for colonization (moraine ridges and deglaciated forelands), cooler temperatures (debris-covered glaciers, rock glaciers, nivation niches or snow patches, ice caves), a vertical range that facilitates dispersal (alpine corridors) and a large variety of niches (alpine composite debris cones). Taken together, these landforms provide a very wide range of habitats, increasing the likelihood that any given alpine species could have a favorable spot to which it could disperse. These relations are indicated in the figure from the paper, shown below, which demonstrates that the geomorphological heterogeneity—the diversity of habitats within and across landforms—promotes the survival of species.

The relation of geomorphological diversity to species survival (Source: Gentili et al./Ecological Complexity).
The relation of geomorphological diversity to species survival (Source: Gentili et al./Ecological Complexity).

The researchers note that these glacial and pre-glacial landforms are potential microrefugia for alpine plants under warming conditions. They recognize that human intervention—purposive translocation of plants—may assist in the survival of species. In addition, they point out that the plant species themselves may adapt genetically to changing environmental conditions. They conclude by suggesting that researchers could profitably direct their attention to evolutionary processes within this geomorphologically complex and climatically dynamic environment, seeing whether species, pressed by climate change, can adapt, or even evolve into new species.

Saxigrada bryoides living on debris-covered glaciers (Source: /Flickr).
Saxigrada bryoides living on debris-covered glaciers (Source: Benoit Deniaud/Flickr).
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Roundup: Nepal Symposium, Microrefugia, Climate Change

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Symposium on Glaciology in High-Mountain Asia (1 – 6 March, 2015)

“The high mountains of Asia are estimated to contain one of the greatest concentrations of glacier ice outside the polar regions, and are the headwaters of rivers which support agriculture and livelihoods of over one billion people. Changes in snow, ice, and permafrost due to climatic changes will impact water resources, ecosystems and hydroelectric power generation, and will aggravate natural hazards. To understand these impacts, the symposium will provide a forum to discuss advances in measurements, modeling, and interpretation of glaciological and cryospheric changes in high mountain Asia.”

Read more about this International Symposium in Kathmandu, Nepal.

 

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Potential Warm-Stage Microrefugia for Alpine Plants

“In Alpine regions, geomorphologic niches that constantly maintain cold-air pooling and temperature inversions are the main candidates for microrefugia. Within such microrefugia, microhabitat diversity modulates the responses of plants to disturbances caused by geomorphologic processes and supports their aptitude for surviving under extreme conditions on unstable surfaces in isolated patches. Currently, European marginal mountain chains may be considered as examples of macrorefugia where relict boreo-alpine species persist within peculiar geomorphological niches that act as microrefugia.”

Read more about this article.

 

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Mountains and Climate Change

“Large mountain ranges often act as climatic barriers, with humid climates on their windward side and semi-deserts on their lee side. Due to their altitudinal extent, many mountain regions intersect important environmental boundaries such as timber lines, snow lines or the occurrence of glaciers or permafrost. Climatically induced changes in these boundaries could possibly trigger feedback processes affecting the local climate. For instance, a rising snow line and thawing permafrost could increase the risk of natural hazards as well as accelerate warming trends due to lower reflectance. Changes in these boundaries can have sharp consequences for ecosystems and can influence natural hazards, economic potential and land use.”

Read more about this article.

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