A glacial refugium (plural glacial refugia) is a geographic region which made possible the survival of

flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...

and

fauna Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and '' funga'', respectively. Flora, fauna, funga and other forms of life are collectively ...

during

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...

s and allowed for post-glacial re-colonization. Different types of glacial refugia can be distinguished, namely

nunatak A nunatak (from Inuit language, Inuit ) is the summit or ridge of a mountain that protrudes from an ice field or glacier that otherwise covers most of the mountain or ridge. They often form natural pyramidal peaks. Isolated nunataks are also cal ...

, peripheral, and lowland.Holderegger, R., Thiel-Egenter, C. (2009): A discussion of different types of glacial refugia used in mountain biogeography and phytogeography. Journal of Biogeography 36, 476-480. Glacial refugia have been suggested as a major cause of floral and faunal distribution patterns in both temperate and tropical latitudes. With respect to disjunct populations of modern-day species, especially in birds, doubt has been cast on the validity of such inferences, as much of the differentiation between populations observed today may have occurred before or after their restriction to refugia. In contrast, isolated geographic locales that host one or more

critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

species (regarded as paleoendemics or glacial relicts) are generally uncontested as bona fide glacial refugia.

Identification

Traditionally, the identification of glacial refugia has occurred through palaeoecological analysis, which examines fossil organisms and their remains to determine the origins of modern taxa. For example, paleoecological approaches have been used to reconstruct the distributions of pollen in Europe for the 13,000 years since the last glaciation. Researchers in this case ultimately established the spread of forest trees from the mountainous southern fringe of Europe, which suggests that this area served as a glacial refugium during this time.

Types

Four distinct types of glacial refugium have been identified:

Hot spring oases

This type of refugium is created by an influx of hydrothermal waters which maintains a humid and warm microclimate that allowed thermophilous trees like oak (Quercus), linden (Tilia), and common ash (Fraxinus excelsior) to survive the last ice age in Central Europe.

Nunatak

A nunatak is a type of glacial refugium located on the snow-free, exposed peaks of mountains, which lie above the ice sheet during glaciations. The identification of ‘diversity hotspots’ in areas that should have been migration regions during major glacial episodes is evidence for nunatak glacial refugia. For example, the

Monte Rosa Monte Rosa (; ; ; or ; ) is a mountain massif in the eastern part of the Pennine Alps, on the border between Italy (Piedmont and Aosta Valley) and Switzerland (Valais). The highest peak of the massif, amongst several peaks of over , is the D ...

mountain ranges, the

Avers Avers (; , ) is a high Alpine valley region and a municipality in the Viamala Region in the Swiss canton of Graubünden. It includes Juf, the highest-altitude year-round settlement in Europe. History Avers is first mentioned in 1292 as ''An ...

, and the

Engadin The Engadin or Engadine (;This is the name in the two Romansh idioms that are spoken in the Engadin, Vallader and Puter, as well as in Sursilvan and Rumantsch Grischun. In Surmiran, the name is ''Nagiadegna'', and in Sutsilvan, it is ''Gidegna'' ...

e and the Bernina are all floristically rich proposed nunatak regions, which are indicative nunatak glacial survival.

Peripheral

Like nunataks, peripheral glacial refugia exist within mountain systems; they differ in that they are located at the borders of mountain systems. Evidence for peripheral refugia can be found along the borders of the

Carpathian Mountains The Carpathian Mountains or Carpathians () are a range of mountains forming an arc across Central Europe and Southeast Europe. Roughly long, it is the third-longest European mountain range after the Ural Mountains, Urals at and the Scandinav ...

Pyrenees The Pyrenees are a mountain range straddling the border of France and Spain. They extend nearly from their union with the Cantabrian Mountains to Cap de Creus on the Mediterranean coast, reaching a maximum elevation of at the peak of Aneto. ...

, and European Alps, all of which were once glaciated mountain systems. For example, using the amplified fragment length polymorphism (AFLP) technique, researchers have inferred survival of ''Phyteuma globulariifolium'' in peripheral refugia in the European Alps.

Lowland

Peak glacial refuges eastern North America

Lowland glacial refugia, unlike nunatak and peripheral glacial refugia, are found at low elevations rather than in mountains. Situated beyond the limits of ice shields, lowland refugia have been identified for several plant and animal species. In Europe, for example, researchers using allozyme analysis have been able to confirm the continuous distribution of '' Zygaena exulans'' in between the foothills of the Pyrenees and the Alps during the last ice age. In eastern North America, lowland glacial refugia along the Atlantic and Gulf Coasts host

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

plants — some of which are rare, even endangered, and others entail the most southerly disjunct populations of plants that commonly appear only hundreds of miles to the north. Major rivers draining southward from the

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

are associated with a gradation of paleoendemic tree species. These range from the extinct Critchfield spruce near the outlet of the

Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...

, to extinct-in-the-wild ''Franklinia'' along the

Altamaha River The Altamaha River is a major river in the U.S. state of Georgia (U.S. state), Georgia. It flows generally eastward for from its Source (river or stream), origin at the confluence of the Oconee River and Ocmulgee River towards the Atlantic Oce ...

, to the critically endangered Florida torreya and Florida yew at the downstream end of the

Chattahoochee River The Chattahoochee River () is a river in the Southeastern United States, Southeastern United States. It forms the southern half of the Alabama and Georgia (U.S. state), Georgia border, as well as a portion of the Florida and Georgia border. It ...

system. (See illustration at right.)

References

{{Reflist Biogeography Ecology Glaciers