Alvar Cawén - Omakuva (1923)
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An alvar is a biological environment based on a
limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
plain In geography, a plain, commonly known as flatland, is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and ...
with thin or no soil and, as a result, sparse grassland vegetation. Often flooded in the spring, and affected by drought in midsummer, alvars support a distinctive group of prairie-like plants. Most alvars occur either in northern Europe or around the
Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...
in North America. This stressed habitat supports a community of rare plants and animals, including species more commonly found on
prairie Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the ...
grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...
s.
Lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...
and
moss Mosses are small, non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Wilhelm Philippe Schimper, Schimp. 1879) may also refer to the parent group bryo ...
es are common species. Trees and bushes are absent or severely stunted. The primary cause of alvars is the shallow exposed bedrock. Flooding and drought, as noted, add to the stress of the site and prevent many species from growing. Disturbance may also play a role. In Europe, grazing is frequent, while in North America, there is some evidence that fire may also prevent encroachment by forest. The habitat also has strong competition gradients, with better competitors occupying the deeper soil and excluding other species to less productive locations. Crevices in the limestone provide a distinctive habitat which is somewhat protected from grazing, and which may provide habitat for unusual ferns such as ''
Pellaea atropurpurea ''Pellaea atropurpurea'', commonly known as purple-stem cliffbrake or just purple cliffbrake, is a fern native to North and Central America. ''Brake'' is an old word for fern, related to the word ''bracken''. Like many other members of the Pterid ...
''. Bare rock flats provide areas with extremely low competition that serve as refugia for weak competitors such as the sandwort '' Minuartia michauxii'' and '' Micranthes virginiensis''. In a representative set of four Ontario alvars, seven habitat types were described. From deep to shallow soil these were: tall grassy meadows, tall
forb A forb or phorb is a herbaceous flowering plant that is not a graminoid (grass, sedge, or rush). The term is used in botany and in vegetation ecology especially in relation to grasslands and understory. Typically, these are eudicots without woo ...
-rich meadows, low grassy meadows, low forb-rich meadows, dry grassland, rock margin grassland and bare rock flats. Alvars comprise a small percentage of the Earth's
ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
s by land extent. Although some 120 exist in the North American Great Lakes region, in total there are only about left across the entire Great Lakes basin, and many of these have been degraded by agriculture and other human uses. More than half of all remaining alvars occur in Ontario. There are smaller areas in New York, Michigan, Ohio, Wisconsin and Quebec. In
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
, alvars provide habitat for birds such as
bobolink The bobolink (''Dolichonyx oryzivorus'') is a small New World blackbird and the only member of the genus ''Dolichonyx''. An old name for this species is the "rice bird", from its tendency to feed on cultivated grains during winter and migration. ...
s,
eastern meadowlark The eastern meadowlark (''Sturnella magna'') is a medium-sized icterid bird, very similar in appearance to its sister species, the western meadowlark. It occurs from eastern North America to northern South America, where it is also most widespr ...
s,
upland sandpiper The upland sandpiper (''Bartramia longicauda'') is a large sandpiper, closely related to the curlews. Older names are the upland plover and Bartram's sandpiper. In Louisiana, it is also colloquially known as the papabotte. It is the Monotypic tax ...
s,
eastern towhee The eastern towhee (''Pipilo erythrophthalmus''), also known as chewink, joree, or joree bird, is a large American sparrow, New World sparrow. The taxonomy of the towhees has been under debate in recent decades, and formerly this bird and the spo ...
s,
brown thrasher The brown thrasher (''Toxostoma rufum''), sometimes erroneously called the brown thrush or fox-coloured thrush, is a bird in the family Mimidae, which also includes the Catbird, New World catbirds and mockingbirds. The brown thrasher is abundant ...
s and
loggerhead shrike The loggerhead shrike (''Lanius ludovicianus'') is a passerine bird in the family Laniidae. It is the only member of the shrike family endemic to North America; the related northern shrike (''L. borealis'') occurs north of its range, however it ...
s whose habitat is declining elsewhere. Rare plants include Kalm's lobelia (''Lobelia kalmii''), Pringle's aster (''Symphyotrichum pilosum'' var. ''pringlei''), juniper sedge (''
Carex juniperorum ''Carex juniperorum'', the juniper sedge, is a perennial flowering plant native to North America, first described by botanist William J. Crins in 1993. ''C. juniperorum'' is in the ''Cyperaceae'' (sedge) family, and is closely related to '' C ...
''), lakeside daisy (''
Hymenoxys acaulis ''Tetraneuris acaulis'' is a North American species of flowering plants in the sunflower family. It is known by many common names in English including stemless four-nerve daisy, stemless hymenoxys, butte marigold, and stemless rubberweed. Descri ...
''), ram's-head lady's-slipper (''Cypripedium arietinum''), and dwarf lake iris (''Iris lacustris''). Also associated with alvars are rare
butterflies Butterflies are winged insects from the lepidopteran superfamily Papilionoidea, characterized by large, often brightly coloured wings that often fold together when at rest, and a conspicuous, fluttering flight. The oldest butterfly fossi ...
and
snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...
s. The use of the word "alvar" to refer to this type of environment originated in
Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
. The largest alvar in Europe is located on the Swedish island of
Öland Öland (, ; ; sometimes written ''Oland'' internationally) is the second-largest Swedish island and the smallest of the traditional provinces of Sweden. Öland has an area of and is located in the Baltic Sea just off the coast of Småland. ...
. Here the thin soil mantle is only 0.5 to 2.0 centimeters thick in most places and in many extents consists of exposed limestone slabs. The landscape there has been designated a
UNESCO The United Nations Educational, Scientific and Cultural Organization (UNESCO ) is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) with the aim of promoting world peace and International secur ...
World Heritage Site World Heritage Sites are landmarks and areas with legal protection under an treaty, international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural ...
. There are other more local names for similar landforms, such as a pavement barren, although this term is also used for similar
landform A landform is a land feature on the solid surface of the Earth or other planetary body. They may be natural or may be anthropogenic (caused or influenced by human activity). Landforms together make up a given terrain, and their arrangement ...
s based on
sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
. In the United Kingdom the exposed landform is called a
limestone pavement A limestone pavement is a natural karst landform consisting of a flat, incised surface of exposed limestone that resembles an artificial Sidewalk, pavement. The term is mainly used in the UK and Ireland, where many of these landforms have devel ...
and thinly covered limestone is known as
calcareous grassland Calcareous grassland (or alkaline grassland) is an ecosystem associated with thin basic soil, such as that on chalk and limestone downland. There are large areas of calcareous grassland in northwestern Europe, particularly areas of southern Engla ...
.


European alvar locations

*
Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
**
Öland Öland (, ; ; sometimes written ''Oland'' internationally) is the second-largest Swedish island and the smallest of the traditional provinces of Sweden. Öland has an area of and is located in the Baltic Sea just off the coast of Småland. ...
 –
Stora Alvaret Stora Alvaret (; "the Great Alvar") is an alvar, a barren limestone terrace, in the southern half of the island of Öland, Sweden. Stora Alvaret is a dagger shaped expanse almost long and about at the widest north end. The area of this formatio ...
 – largest alvar extent in Europe **
Gotland Gotland (; ; ''Gutland'' in Gutnish), also historically spelled Gottland or Gothland (), is Sweden's largest island. It is also a Provinces of Sweden, province/Counties of Sweden, county (Swedish län), Municipalities of Sweden, municipality, a ...
**
Västergötland Västergötland (), also known as West Gothland or the Latinized version Westrogothia in older literature, is one of the 25 traditional non-administrative provinces of Sweden (''landskap'' in Swedish), situated in the southwest of Sweden. Vä ...
 – several locations on limestone mountain
Kinnekulle Kinnekulle is a flat-topped mountain in the county of Västergötland, southwestern Sweden, on the eastern shore of lake Vänern. Its highest point is above sea level. The mountain is long and wide at the top. Geology Despite its enormous ...
, smaller fragments on Falbygden, e.g. in Dala and Högstena parishes *
Estonia Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Ru ...
** Alvars are distributed along the whole northern coast of Estonia from approx. the town of
Paldiski Paldiski is a seaside Populated places in Estonia, town in northwestern Estonia, located on the Pakri Peninsula and adjacent Pakri Islands, Pakri islands in the Gulf of Finland of the Baltic Sea. It is the administrative centre of the Lääne- ...
to
Sillamäe Sillamäe (Estonian for 'Bridge Hill'; also known by the Germanised names of ''Sillamäggi'' or ''Sillamägi'') is a town in Ida-Viru County in the northeastern part of Estonia, on the southern coast of the Gulf of Finland. It has a population o ...
, wherever limestone comes to the surface near the seashore (see
Baltic Klint The Baltic Klint (Clint, Glint; , , ) is an erosional limestone escarpment and cuesta on several islands of the Baltic Sea, in Estonia, in Leningrad Oblast of Russia and in the islands of Gotland and Öland of Sweden. It was featured on the reve ...
), as well as on the islands of the
West Estonian archipelago The West Estonian archipelago (, also Moonsund archipelago) is a group of Estonian islands located in the Baltic Sea around Väinameri. The total area is about . The archipelago is composed of the islands Saaremaa, Hiiumaa, Muhu, Vormsi and ab ...
. Estonia used to be home to approximately one third of the world's alvars; however, the total area of alvars has decreased from 43,000
hectare The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), that is, square metres (), and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. ...
s in the 1930s to 12,000 hectares in 2000, and approximately 9,000 hectares in 2010. Estonian alvars are home to 267
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
vascular plant Vascular plants (), also called tracheophytes (, ) or collectively tracheophyta (; ), are plants that have lignin, lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified Ti ...
s, approximately one fifth of which are protected. There are also 142 species of
bryophyte Bryophytes () are a group of embryophyte, land plants (embryophytes), sometimes treated as a taxonomic Division (taxonomy), division referred to as Bryophyta ''Sensu#Common qualifiers, sensu lato'', that contains three groups of non-vascular pla ...
s and 263 species of
lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...
s. The Estonian government has committed itself to protect at least 9,800 hectares of the country's alvars as part of the
Natura 2000 Natura 2000 is a network of nature protection areas in the territory of the European Union. It is made up of Special Areas of Conservation and Special Protection Areas designated under the Habitats Directive and the Birds Directive, respectiv ...
network. The
Loopealse Loopealse (Estonian for ''"Alvar"'', literally ''"Above Alvar"'') is a subdistrict () in the district of Lasnamäe, Tallinn, the capital of Estonia Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered ...
subdistrict of
Tallinn Tallinn is the capital city, capital and List of cities in Estonia, most populous city of Estonia. Situated on a Tallinn Bay, bay in north Estonia, on the shore of the Gulf of Finland of the Baltic Sea, it has a population of (as of 2025) and ...
is named after alvar. ** Vardi Nature Reserve in
Rapla County Rapla County ( or ''Raplamaa'') is one of the fifteen counties of Estonia. It is situated in the north-western part of the country and borders Järva County to the east, Pärnu County to the south, Lääne County to the west, and Harju County to ...
is an Estonian nature reserve especially designated to protect one of the more representative alvar areas of Estonia. *
England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...
**
Cumbria Cumbria ( ) is a ceremonial county in North West England. It borders the Scottish council areas of Dumfries and Galloway and Scottish Borders to the north, Northumberland and County Durham to the east, North Yorkshire to the south-east, Lancash ...
and North
Yorkshire Yorkshire ( ) is an area of Northern England which was History of Yorkshire, historically a county. Despite no longer being used for administration, Yorkshire retains a strong regional identity. The county was named after its county town, the ...
– under protection in the UK Biodiversity Action Plan *
Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...
**
The Burren The Burren ( ; ) is a karst/glaciokarst landscape centred in County Clare, on the west coast of Republic of Ireland, Ireland.
, a large alvar in northwest
County Clare County Clare () is a Counties of Ireland, county in the Provinces of Ireland, province of Munster in the Southern Region, Ireland, Southern part of Republic of Ireland, Ireland, bordered on the west by the Atlantic Ocean. Clare County Council ...
Sarve loopealne Hiiumaal.jpg, Sarve alvar in
Hiiumaa Hiiumaa ( , ) is the second largest island in Estonia and is part of the West Estonian archipelago, in the Baltic Sea. It has an area of 989 km2 and is 22 km from the Estonian mainland. Its largest town is Kärdla. It is located within ...
island Väike-Pakri loopealsel.jpg, Alvar in
Väike-Pakri Pakri islands (, ) are two Estonian islands in the Gulf of Finland of the Baltic Sea: Suur-Pakri and Väike-Pakri ( and ). Administratively the islands are part of the town of Paldiski. For centuries the two islands were inhabited by Estonian Swe ...
island Österplana hed vegetation.jpg, Sparse vegetation,
Kinnekulle Kinnekulle is a flat-topped mountain in the county of Västergötland, southwestern Sweden, on the eastern shore of lake Vänern. Its highest point is above sea level. The mountain is long and wide at the top. Geology Despite its enormous ...
,
Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
Limestone pavement above Malham Cove.jpg, Limestone pavement at
Malham Cove Malham Cove is a large curved limestone formation north of the village of Malham, North Yorkshire, England. It was formed by a waterfall carrying meltwater from glaciers at the end of the last Last glacial period, Ice Age more than 12,000 year ...
, UK


Some North American alvar locations

*The ''rare'' Charitable Research Reserve –
Cambridge Cambridge ( ) is a List of cities in the United Kingdom, city and non-metropolitan district in the county of Cambridgeshire, England. It is the county town of Cambridgeshire and is located on the River Cam, north of London. As of the 2021 Unit ...
,
Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...
*
Lake Erie Lake Erie ( ) is the fourth-largest lake by surface area of the five Great Lakes in North America and the eleventh-largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and also has the shortest avera ...
** Kelley's Island,
Ohio Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...
– North Shore Alvar State Nature Preserve **
Marblehead, Ohio Marblehead is a village (United States)#Ohio, village in Ottawa County, Ohio, United States. The population was 865 at the 2020 United States census, 2020 census. It sits at the tip of the Marblehead Peninsula, which divides Lake Erie proper from ...
– mostly destroyed by limestone quarrying **
Pelee Island Pelee may refer to: *Pelee, Ontario, an island in Lake Erie, Canada *Point Pelee National Park, a park in Ontario, Canada *Mount Pelée, a volcano in Martinique *Peleus In Greek mythology, Peleus (; Ancient Greek: Πηλεύς ''Pēleus'') was ...
,
Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...
– Stone Road Alvar Nature Reserve *
Lake Huron Lake Huron ( ) is one of the five Great Lakes of North America. It is shared on the north and east by the Canadian province of Ontario and on the south and west by the U.S. state of Michigan. The name of the lake is derived from early French ex ...
**Maxton Plains Proposed Natural Area,
Drummond Island Drummond may refer to: Places Antarctica * Drummond Peak, King Edward VII Land * Drummond Glacier, Graham Land Canada * Drummond (federal electoral district), a Quebec federal riding * Drummond (provincial electoral district), Quebec ...
,
Michigan Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...
**Belanger Bay Alvar,
Manitoulin Island Manitoulin Island ( ) is an island in Lake Huron, located within the borders of the Provinces and territories of Canada, Canadian province of Ontario, in the bioregion known as Laurentia (bioregion), Laurentia. With an area of , it is the Lake ...
, Ontario **Quarry Bay Nature Reserve, Manitoulin Island, Ontario **Bruce Alvar Nature Reserve,
Bruce Peninsula The Bruce Peninsula is a peninsula in Ontario, Canada, that divides Georgian Bay of Lake Huron from the lake's main basin. The peninsula extends roughly northwestwards from the rest of Southwestern Ontario, pointing towards Manitoulin Island, wi ...
, Ontario **Baptise Harbour Nature Reserve, Bruce Peninsula, Ontario **
Misery Bay Misery Bay is a freshwater bay on Manitoulin Island in Ontario. It is noted for its alvars and large dolomite pavements ground flat by glaciers. It also contains grykes and ecologically significant wetlands. History Misery Bay was covered by ...
Provincial Park, Manitoulin Island, Ontario *
Lake Michigan Lake Michigan ( ) is one of the five Great Lakes of North America. It is the second-largest of the Great Lakes by volume () and depth () after Lake Superior and the third-largest by surface area (), after Lake Superior and Lake Huron. To the ...
**Red Banks Alvar,
Red Banks, Brown County, Wisconsin Red Banks is an unincorporated community located in the town of Scott, Brown County, Wisconsin Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Mi ...
*
Lake Ontario Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north, west, and southwest by the Canadian province of Ontario, and on the south and east by the U.S. state of New York (state), New York. The Canada–United Sta ...
**Carden Plain Alvar, City of Kawartha Lakes, Ontario, including
Carden Alvar Provincial Park Carden Alvar Provincial Park is a provincial park located in the Kawartha Lakes in Central Ontario, Canada. Alvars are globally rare ecosystems found exclusively in Northern Europe and the Great Lakes region of North America. The park is classi ...
**Chaumont Barrens Preserve, New York **Three Mile Creek Barrens, New York ** Burnt Lands Alvar, Almonte, Ontario ** Balsam Lake Indian Point Provincial Park, Ontario *
Quebec Quebec is Canada's List of Canadian provinces and territories by area, largest province by area. Located in Central Canada, the province shares borders with the provinces of Ontario to the west, Newfoundland and Labrador to the northeast, ...
** Quyon **Alvar d' Aylmer *
Manitoba Manitoba is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population ...
**
Interlake Interlake was a provincial electoral division in the Canadian province of Manitoba. It was created by redistribution in 1979, and has formally existed since the 1981 provincial election. Previously, much of the Interlake region was include ...


See also

* * * * * * *


References


External links

{{Commons-inline, Alvar (landform), Alvar * http://www.epa.gov/ecopage/shore/alvars/ Alkaline soils Habitats Landforms Types of soil Alpine flora Gotland Geography of Gotland County