Location and General Description
The Great Lakes Basin is situated in western Mongolia and surrounded by the high Altai, Khangai and Tagna Tuva mountain ranges. The basin is 600-650 km in length with a width of 200-250 km in the north and 60-100 km in the south. The basin belongs to the Central Asia Internal Drainage Basin. Within the basin are a series of large lakes, namely, the Uvs, Hyargas, Khar-Us, Khar, Airag, and Shargyn tsagaan that are all fed by large rivers flowing from the Khangai and Altai mountain ranges. The Basin is divided into four parts: the Uvs, Hyargas, Khar-Us and Sharga depressions. The average elevation on Khar-Us lake is 1153 m, Hyargas lake 1028 m, Uvs lake 759 m, and Shargyn lake depression 948-1700 m. The climate of the Great Lakes Basin is generally arid and characterized by extremely low temperatures and low, erratic rainfall. Winters are long and cold with mean temperatures below 0° C. Spring is dry and windy while summers are warm to hot. The annual mean temperature is - 2°C, with mean monthly temperatures ranging from -24°C in January to 20°C in July (Ulziikhutag 1989). Average annual precipitation is 50-150 mm. The Uvs lake basin is the center of the Asian anticyclone and is known as one of the coldest places in Asia with the lowest temperature recorded at -58°C (Finch 1999).
The lower parts of the mountains are separated by wide, dry valleys that gently slope to the rivers and lakes. The valleys are interspersed with salt pans, small lakes and small hills. Jagged outcrops are widespread in the valley floor. The lakes are surrounded by sparsely vegetated desert and semi-desert, and occasional saltmarshes. The eastern parts of the basin are covered with large dune areas.
The vegetation of the basin is sparse and mainly characterized by semi-shrubs, shrubs (especially Caragana leucophloea) up to 0.5 m tall and some grasses (especially Stipa spp.). Xerophytic and in some places halophytic plant communities of the desert and semi-desert are dominant, with azonal vegetation in the larger river-valleys and around the lakes. So far 554 species of 62 families have been recorded from the Basin. Nineteen plant species that occur within Mongolia are recorded only in the Basin, 13 that are endemic to the Basin and 22 that are listed in the Mongolian Red Data Book
On the upper slopes the Anabasis brevifolia desert dominates, with a plant canopy cover of 3 to 20 %. Characteristic species here are Stipa glareosa and Hyppolitia achilleoide. Lower slopes are dominated by Caragana lecucophloea communities. The semi-desert (desert steppe) which covers most of the Great Lakes Basin has three major plant communities: the Oxytropis aciphylla - Caragana leucophloea, the Artemisia rutifolia - Caragana leucophloea, and the Amygdalus pedunculata - Caragana lecucophloea community. The plant canopy cover in these shrub semi-desert communities ranges from 15 to 50%. The Achnatherum splendens community occupies the transition zone between the vegetation of the semi-desert and the vegetation of the grazing pastures in the river valleys. This community is often interspersed with shrubs (Caragana spinosa and Halimodendron halodendron). In the river valleys between the Achnatherum splendens community and the grazing pastures, dense stands of bushes (Halimodendron halodendron and Caragana spinosa) often form long bands. Upper areas of the river valleys and areas around Har Us Nuur are dominated by the Aneurolepidium pseudagropyrum grass community. Along the Khovd and Buyant rivers Salix viminalis bushes/trees form dense, but now degraded stands. Large areas of the river valleys and lake shores of the Basin have been used as grazing pastures during the last centuries. On these degraded lands a grazing "lawn" developed, with Potentilla anserina as the dominant species. Lower parts of these areas show a high concentration of salt, where halophytic species are dominant (Bräunlich 1995). Large areas along the Khar-Us lake shore are covered with reedbeds, dominated by Phragmites communis. Desert steppe, with Nanophyton, Salsola passerina, and Artemisia frigida, dominates in the Uvs lake basin. Reaumuria soongorica and Anabasis spp. dominate in Hyargas while dominant communities in Shargyn consist of Haloxylon ammodendron (Buyan-Orshikh 1978).
The fauna of the Great Lakes Basin consists mainly of species adapted to desert/semi-desert habitats and wetlands. Rodents characteristic of the Basin include Meriones unguiculatus, Dipus sagitta, Citellus erithrogenus, and Phodopus roborovskii. Mountainous areas are inhabited by Ovis ammon and Capra sibirica, reed-bed around Khar-Us lake by Sus scrofa, and lower steppe by Procapra guttorosa and Gazella subgutturosa. Predator species include: Canis lupus, Vulpes vulpes, Vulpes corsac, Otocolobus manul, Mustela altaica, Mustela erminea, Mustela eversmanni, and Martes foina. Shores of lakes and wetlands are important habitat for water bird species such as Pelecanus crispus, Platelea leucoridia, Cygnus cygnus, Cygnopsis cygnoides, Oxyura leucocephala Phalacrocorax carbo, Anser anser, Tadorna ferruginea, Anas platyrhynchos, Fulica atra and a variety of migratory birds. Milvus migrans and Oenanthe deserti are found throughout the ecoregion and Passer domesticus near urban areas.
Common amphibians and reptiles include: Phrynocephalus versicolor, Elaphe dione, and Agkistrodoon halus. Common fishes in lakes and rivers are Oreoleuciscus potanini, Thymallus brevirostris, Coregonus peled, Thymallus arcticus arcticus, Nemachilus barbatulus toni, and Nemachilus strauchi.
Insect groups (e.g., Orthoptera, Homoptera, Tenebrionidae, Meloidae, Curculionidae, Scarabaeidae) that are well adapted to the arid desert steppe are closely associated with plants such as Caragana spp. and Artemisia spp. that dominate the basin.
Some of the last vast reedbeds of central Asia remain here, and the sharp contrast of the semi-arid desert-steppe bordering the diverse wetlands makes the basin a unique landscape. Several globally endangered species are protected here including one of the two last remaining populations of Mongolian saiga (Saiga tatarica mongolica) along with dalmatian pelican (Pelecanus crispus) and snow leopard (Uncia uncia).
Because Uvs Lakes Basin contains an interesting collection of different ecosystems that are scientifically important, it is one of 10 sites in the world selected for a global climate change study as part of the international Geosphere and Biosphere programs (Shiirevdamba 1998).
The semi-arid Great Lakes Basin ecoregion receives protection with the inclusion of Uvs Lake Basin Strictly Protected Area (SPA) (7,125,000 ha), and Khar Us Nuur (8,503,000 ha) and Khyargas Nuur (approximately 3,200,000 ha) National Parks.
Types and Severity of Threats
Overgrazing, population growth, deforestation of riparian areas and hydroelectric development plans seriously threaten the ecoregion. In the 1990s Mongolia turned to a market economy which resulted in the collapse of a centralized infrastructure and a sharp increase in unemployment. A significant number of people turned to livestock agriculture which has resulted in overgrazing, pasture degradation, and the potential of desertification in vulnerable areas.
Justification of Ecoregion Delineation
Between the Mongolian Altai and Khangai Mountains is a large closed depression with a series of freshwater and salt lakes. The boundary delineation corresponds to the desert steppe of the Great Lakes region in Hilbig (1995) and the Mongolia Ministry for Nature and Environment (1996).
Buyan-Orshikh, K. 1978. Flora and vegetation in sand dunes of the great lakes basin. Study on the Flora and Vegetation of the Mongolian People’s Republic. Volume 2. (in Mongolian).
Finch, C., editor. 1999. Mongolia's wild heritage. Mongolia Ministry for Nature and Environment, UNDP, GEF and WWF. Avery Press, Boulder.
Hilbig, W. 1995. The Vegetation of Mongolia. SPB Academic Publishing, Amsterdam.
Mongolia Ministry for Nature and Environment, United Nations Development Programme (UNDP)/Global Environment Facility (GEF), and World Wide Fund for Nature (WWF). 1996. Mongolias Wild Heritage, edited by C. Finch. Avery Press, Boulder
National Atlas of the Mongolian People’s Republic. 1990. Union of Soviet Socialist Republics.
Shiirevdamba, T. 1998. Biological Diversity in Mongolia. First national report, Ulaanbaatar.
Ulziihutag N. 1989. Flora of Mongolia, Ulaanbaatar (in Mongolian).
Prepared by: Ehnvee Devee
Reviewed by: Batbold D. Otgoid