The Mývatn area has unique geological and biological conservation values. Precipitation is trapped by the porous volcanic bedrock and moves beneath the surface until it reappears in a series of springs which supply systems of rivers and lakes. The largest of these is the wetland area of Mývatn and Laxá. Lake Mývatn (37 km²) is situated 278 meters above sea level and contains more than 50 islands. The landscape around the lake and in many of the islands is dominated by perfectly shaped pseudo craters, formed by steam explosions as hot lava flowed into the lake some 2300 years ago. The best known of the craters are Skútustaðagígar, which has a special protection status.
The name of the lake, Mývatn, derives from the vast numbers of midges (aquatic insects) that emerge from the lake, forming impressive mating swarms on its shores.
Mývatn and Laxá have one of the world's richest populations of breeding aquatic birds. In all 115 species of birds have been recorded in the area, including 28 species of ducks. Fifteen species of ducks breed in the area regularly. The most common ducks being tufted duck (Aythya fuligula), scaup (Aythya marila) and wigeon (Anas penelope). Other common ducks are Barrow's goldeneye (Bucephala islandica), red-breasted merganser (Mergus serrator), common scoter (Melanitta nigra) and mallard (Anas platyrhynchos). Three of the breeding ducks are rare elsewhere in Iceland. Mývatn along with its immediate surroundings, is the only known breeding area for Barrow's goldeneye in Europe, and the harlequin duck (Histrionicus histrionicus) has its easternmost breeding area here. In addition to ducks, over 300 pairs of Slavonian grebe (Podiceps auritius) breed there. Other waterbirds include whooper swans (Cygnus cygnus), red-necked phalaropes (Phalaropus lobatus), great northern divers (Gavia immer) and red-throated divers (Gavia stellata).
The rich bird life principally owes its presence to the abundant supply of nutrients in the lake, with its abundant primary production and huge quantities of insects and other small creatures, providing rich feeding for the birds. The size of the lake, its extensive shallows, many islands, long shoreline, dry climate and varied landscape are among the factors contributing to the rich bird life.
Considering the latitude, the climate is favourable. The average temperature in January is -0.2°C and the warmest month, July, has an average temperature of 10.2°C. The area is also one of the sunniest in Iceland and has an annual precipitation of only 400 mm. Since Mývatn is a shallow lake (maximum 4 meters, except for the part where siliceous sediments (diatomite) have been extracted), sufficient sunlight penetrates to sustain rich bottom vegetation, including lake balls that are a rare variety of green algae (Aegagropila linnaei).
Despite its rather small size, the Mývatn area embodies enormous contrasts. It's backdrop of desolate volcanic landscape is contrasted by the green and lush vegetation on the lake shore and along the river Laxá. The shores owe their greenness to a fertilizing effect of the aquatic insects as they carry nutrients from lake to land.
The volcanic nature of the area is part of the rifting occurring along the Mid-Atlantic Ridge, which stretches as a zone of active volcanism through Iceland from coast to coast. An elongated zone of fissures and volcanic craters provides visible proof of the fracturing of the Earth's crust as the American and Eurasian Plates move apart at a rate of 2 cm per year.
Traditionally the Mývatn area is a farming district, but farming activities are now on the decline. About 400 people live there, increasingly basing their livelihood on tourism. Mining activities in the lake, which started in 1967, were halted in 2004.
Lake Mývatn and river Laxá is a unique freshwater ecosystem in the northern hemisphere, situated along the volcanic zone of the Mid-Atlantic Ridge. The area is an outstanding representative of a wetland ecosystem in the high North, recognized worldwide for its beauty, high productivity and luscious bird life. The life history of the lake for the last 2000 years has been identified from lake sediments and has revealed the development of the ecosystem, changes in species composition as well as population dynamics during this long period. The lake is a Ramsar Site and has been protected for nature conservation for nearly 40 years.
Criterion viii. The lake area is dominated by pseudo craters (rootless cones), formed by steam explosions as lava entered a large lake (a precursor of the present Lake Mývatn). Such formations are extremely rare outside Iceland, and the Mývatn craters were the first to be identified as this kind of formation.
Criterion ix. The Mývatn area represents a rare case where nutrients released atop the Mid-Atlantic Ridge fertilise a rich aquatic ecosystem, supporting a wealth of waterfowl and rare plants. The ecosystem is being intensively studied and the most recent findings indicate that its cyclic populations are shaped by unusual population dynamics.
Criterion x. Lake Mývatn and River Laxá are known for their productivity and biodiversity which are greater than in other freshwater habitats at the same latitude. The species composition among aquatic birds is unique in the world (a unique combination of elements from four faunal provinces of the world). Fifteen species of duck permanently breed in the area and occasional breeding has been recorded for several species that are not known to breed elsewhere in Iceland. Mývatn and Laxá are the only breeding areas in Europe for Barrow's golden eye (Bucephala islandica). Several other aquatic birds also nest here, including Slavonian grebe (Podiceps auritus). More than 40 species of midges occur along the lake and river. The American blackfly (Simulium vittatum) has one of its largest known productions in the world in this area. Rare plant species have also been recorded, including lake balls (green algae) that form a community of CD-sized fluffy spheres only found in Mývatn and one other lake in the world.
The Mývatn and Laxá area has been protected since 1973 by special legislation and is now protected under the terms of Act no. 97/2004. This includes the whole watershed area of Lake Mývatn. The protection entails that all constructional activity and other disturbances of the natural environment is prohibited or subject to approval by the Environment Agency of Iceland. The protected area includes all the necessary habitats and elements to sustain the richness and diversity of the area and is considered to be adequate in size for complete representation of features and processes to constitute the wholeness of the area. The naturalness of the area is high and has been enhanced by protection measures such as restoration of a drained wetland area within the site. The area and a part of the province Skútustaðahreppur (200 km²) has the status of a Ramsar Site.
Pseudo craters or rootless cones are extremely rare outside Iceland. They have only been found in Hawaii where lava has entered the ocean (littoral cones). Recently, similar formations have been identified on Mars where lava has flowed over frozen ground.
The birdlife at Mývatn is unique. More species of ducks nest in the area than anywhere else in the world and the lake and river are among the richest bird haunts in the world. Some ducks, which are common in the Mývatn area, are extremely rare elsewhere in North-western Europe.
The duck populations in Lough Neagh in Northern Ireland and Loch Leven in Scotland can partly be compared with those in the Mývatn area. Mývatn is the only known nesting site in Europe for Barrow's golden eye (Bucephala islandica). The bottom fauna in Mývatn has a production that is 8 to 30 times greater than that of other lakes at the same latitude.
The lake balls (green algae) are only found in one other lake in the world, the famous marimo in Lake Akan, Japan.