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55-464: Lake Pátzcuaro lies in an endorheic basin , which does not drain to the sea. A watershed area of 929 square kilometres drains into the lake, of which 126.4 are the water body. The Lake Pátzcuaro watershed extends 50 kilometres east–west and 33 kilometres from north to south. Lake Pátzcuaro lies at an elevation of 1,920 metres, and is the center of the basin and is surrounded by volcanic mountains with very steep slopes. It has an average depth of 5 metres and

110-426: A balance of surface inflows, evaporation and seepage) are often called sinks. Endorheic lakes are typically located in the interior of a landmass, far from an ocean, and in areas of relatively low rainfall. Their watersheds are often confined by natural geologic land formations such as a mountain range, cutting off water egress to the ocean. The inland water flows into dry watersheds where the water evaporates, leaving

165-415: A given ecoregion are more similar to each other than to those of surrounding ecoregions and together form a conservation unit. Freshwater systems include rivers , streams , lakes , and wetlands . Freshwater ecoregions are distinct from terrestrial ecoregions, which identify biotic communities of the land, and marine ecoregions, which are biotic communities of the oceans. A map of Freshwater Ecoregions of

220-573: A high concentration of minerals and other inflow erosion products. Over time this input of erosion products can cause the endorheic lake to become relatively saline (a " salt lake "). Since the main outflow pathways of these lakes are chiefly through evaporation and seepage, endorheic lakes are usually more sensitive to environmental pollutant inputs than water bodies that have access to oceans, as pollution can be trapped in them and accumulate over time. Endorheic regions can occur in any climate but are most commonly found in desert locations. This reflects

275-469: A holistic, "weight-of-evidence" approach where the importance of various factors may vary. An example of the algorithmic approach is Robert Bailey 's work for the U.S. Forest Service, which uses a hierarchical classification that first divides land areas into very large regions based on climatic factors, and subdivides these regions, based first on dominant potential vegetation, and then by geomorphology and soil characteristics. The weight-of-evidence approach

330-798: A large portion of Europe drains to the endorheic Caspian Sea, Europe's wet climate means it contains relatively few terminal lakes itself: any such basin is likely to continue to fill until it reaches an overflow level connecting it with an outlet or erodes the barrier blocking its exit. There are some seemingly endorheic lakes, but they are cryptorheic, being drained either through manmade canals , via karstic phenomena, or other subsurface seepage. A few minor true endorheic lakes exist in Spain (e.g. Laguna de Gallocanta , Estany de Banyoles ), Italy , Cyprus ( Larnaca and Akrotiri salt lakes) and Greece . Many small lakes and ponds in North Dakota and

385-546: A limit of the erosion and deposition processes of nearby areas. Endorheic water bodies include the Caspian Sea , which is the world's largest inland body of water. The term endorheic derives from the French word endoréisme , which combines endo- ( Ancient Greek : ἔνδον éndon 'within') and ῥεῖν rheîn 'flow'. Endorheic lakes (terminal lakes) are bodies of water that do not flow into an ocean or

440-554: A maximum of 11. Its volume is approximately 580 million cubic metres. The Lake Pátzcuaro basin is of volcanic origin. At times it has been part of an open and continuous hydrological system formed by Lake Cuitzeo , Pátzcuaro and Lake Zirahuén , which drained into the Lerma River . Today, like lakes Cuitzeo and Zirahuén, it is a closed basin, although ecologists consider it a sub-basin of the Lerma-Chapala basin. The lake

495-523: A redistribution of water from these hydrologically landlocked basins such that endorheic water loss has contributed to sea level rise , and it is estimated that most of the terrestrial water lost ends up in the ocean. In regions such as Central Asia, where people depend on endorheic basins and other surface water sources to satisfy their water needs, human activity greatly impacts the availability of that water. Large endorheic regions in Africa are located in

550-420: A sea. Most of the water that falls to Earth percolates into the oceans and the seas by way of a network of rivers, lakes, and wetlands . Analogous to endorheic lakes is the class of bodies of water located in closed watersheds (endorheic watersheds) where the local topography prevents the drainage of water into the oceans and the seas. These endorheic watersheds (containing water in rivers or lakes that form

605-517: A set of ecoregions identified by WWF whose conservation would achieve the goal of saving a broad diversity of the Earth's ecosystems, includes a number of areas highlighted for their freshwater biodiversity values. The Global 200 preceded Freshwater Ecoregions of the World and incorporated information from regional freshwater ecoregional assessments that had been completed at that time. Sources related to

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660-407: A web application developed by Resolve and Google Earth Engine. An ecoregion is a "recurring pattern of ecosystems associated with characteristic combinations of soil and landform that characterise that region". Omernik (2004) elaborates on this by defining ecoregions as: "areas within which there is spatial coincidence in characteristics of geographical phenomena associated with differences in

715-605: Is endemic to the basin. Among other aquatic or semi-aquatic animals, several are largely or entirely restricted to the Lake Pátzcuaro system, such as the rough-footed mud turtle of the subspecies tarascense , the essentially harmless Mexican garter snake of the subspecies patzcuaroensis , the fish Pátzcuaro chub ( Algansea lacustris ) and Pátzcuaro allotoca ( Allotoca diazi ), and the dwarf crayfish Cambarellus patzcuarensis . The lake and its surrounding wetlands have undergone significant environmental changes over

770-426: Is analogous to that used for terrestrial ecoregions. Major habitat types are identified: polar, temperate shelves and seas, temperate upwelling, tropical upwelling, tropical coral, pelagic (trades and westerlies), abyssal, and hadal (ocean trench). These correspond to the terrestrial biomes . The Global 200 classification of marine ecoregions is not developed to the same level of detail and comprehensiveness as that of

825-622: Is exemplified by James Omernik's work for the United States Environmental Protection Agency , subsequently adopted (with modification) for North America by the Commission for Environmental Cooperation . The intended purpose of ecoregion delineation may affect the method used. For example, the WWF ecoregions were developed to aid in biodiversity conservation planning, and place a greater emphasis than

880-403: Is one such case, with annual precipitation of 850 mm (33 in) and characterized by waterlogged soils that require draining. Endorheic regions tend to be far inland with their boundaries defined by mountains or other geological features that block their access to oceans. Since the inflowing water can evacuate only through seepage or evaporation, dried minerals or other products collect in

935-526: Is optimal for all taxa. Ecoregions reflect the best compromise for as many taxa as possible. Secondly, ecoregion boundaries rarely form abrupt edges; rather, ecotones and mosaic habitats bound them. Thirdly, most ecoregions contain habitats that differ from their assigned biome . Biogeographic provinces may originate due to various barriers, including physical (plate tectonics, topographic highs), climatic (latitudinal variation, seasonal range) and ocean chemical related (salinity, oxygen levels). The history of

990-601: Is surrounded by extensive wetlands , which have been designated as a Ramsar site since 2005. Cattails and other reedy vegetation are the dominant wetland vegetation, in dense stands over 2 meters tall. Typical wetland plant genera include Typha , Scirpus , Eleocharis , and Cyperus . The dominant species of aquatic vegetation are Potamogeton illinoensis , Scirpus pectinatus , Typha latifolia , T. domingensis , and Nymphaea mexicana . The wetlands are extremely important for birds, both year-round inhabitants and migrating waterfowl. Close to 200 species inhabit

1045-627: The Bonneville flood . The Malheur / Harney lake system in Oregon is normally cut off from drainage to the ocean, but has an outflow channel to the Malheur River . This is presently dry, but may have flowed as recently as 1,000 years ago. Examples of relatively humid regions in endorheic basins often exist at high elevation. These regions tend to be marshy and are subject to substantial flooding in wet years. The area containing Mexico City

1100-608: The Himalayas and the Sahara . The boundaries of ecoregions are often not as decisive or well recognized, and are subject to greater disagreement. Ecoregions are classified by biome type, which are the major global plant communities determined by rainfall and climate. Forests, grasslands (including savanna and shrubland), and deserts (including xeric shrublands ) are distinguished by climate ( tropical and subtropical vs. temperate and boreal climates) and, for forests, by whether

1155-942: The Sahara Desert , the Sahel , the Kalahari Desert , and the East African Rift : Endorheic lakes exist in Antarctica's McMurdo Dry Valleys , Victoria Land , the largest ice-free area. Much of Western and Central Asia is a giant endorheic region made up of a number of contiguous closed basins. The region contains several basins and terminal lakes, including: Other endorheic lakes and basins in Asia include: Australia , being very dry and having exceedingly low runoff ratios due to its ancient soils, has many endorheic drainages. The most important are: Though

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1210-450: The "ecoregion" as a unit of analysis. The " Global 200 " is the list of ecoregions identified by WWF as priorities for conservation . Terrestrial ecoregions are land ecoregions, as distinct from freshwater and marine ecoregions. In this context, terrestrial is used to mean "of land" (soil and rock), rather than the more general sense "of Earth " (which includes land and oceans). WWF (World Wildlife Fund) ecologists currently divide

1265-558: The Earth. The use of the term ecoregion is an outgrowth of a surge of interest in ecosystems and their functioning. In particular, there is awareness of issues relating to spatial scale in the study and management of landscapes . It is widely recognized that interlinked ecosystems combine to form a whole that is "greater than the sum of its parts". There are many attempts to respond to ecosystems in an integrated way to achieve "multi-functional" landscapes, and various interest groups from agricultural researchers to conservationists are using

1320-837: The Northern Great Plains are endorheic, and some have salt encrustations along their shores. Some of Earth's ancient endorheic systems and lakes include: Ecoregion An ecoregion ( ecological region ) is an ecologically and geographically defined area that is smaller than a bioregion , which in turn is smaller than a biogeographic realm . Ecoregions cover relatively large areas of land or water, and contain characteristic, geographically distinct assemblages of natural communities and species . The biodiversity of flora , fauna and ecosystems that characterise an ecoregion tends to be distinct from that of other ecoregions. In theory, biodiversity or conservation ecoregions are relatively large areas of land or water where

1375-552: The Omernik or Bailey systems on floral and faunal differences between regions. The WWF classification defines an ecoregion as: A large area of land or water that contains a geographically distinct assemblage of natural communities that: According to WWF, the boundaries of an ecoregion approximate the original extent of the natural communities prior to any major recent disruptions or changes. WWF has identified 867 terrestrial ecoregions, and approximately 450 freshwater ecoregions across

1430-520: The Spanish conquest. The towns of Ihuatzio , Tzintzuntzan and Pátzcuaro were important Purépecha centers. Endorheic basin An endorheic basin ( / ˌ ɛ n d oʊ ˈ r iː . ɪ k / EN -doh- REE -ik ; also endoreic basin and endorreic basin ) is a drainage basin that normally retains water and allows no outflow to other external bodies of water (e.g. rivers and oceans ); instead,

1485-499: The Supreme Indigenous Council of Michoacán (CSIM) noted that political opportunism, corruption, and a lack of coordination have undermined efforts to clean up the lake. They noted that since 2006 MXN $ 5 billion has been spent, and since 1934, 2,300 studies have been conducted, yet 79% of the inhabitants of Pátzcuaro , Erongarícuaro , Quiroga , and Tzintzuntzan live in poverty and 40% in extreme poverty . In

1540-571: The WWF concept prioritizes biogeography, that is, the distribution of distinct species assemblages. In 2017, an updated terrestrial ecoregions dataset was released in the paper "An Ecoregion-Based Approach to Protecting Half the Terrestrial Realm" led by E. Dinerstein with 48 co-authors. Using recent advances in satellite imagery the ecoregion perimeters were refined and the total number reduced to 846 (and later 844), which can be explored on

1595-523: The World (TEOW), led by D. Olsen, E. Dinerstein, E. Wikramanayake, and N. Burgess. While the two approaches are related, the Bailey ecoregions (nested in four levels) give more importance to ecological criteria and climate zones, while the WWF ecoregions give more importance to biogeography, that is, the distribution of distinct species assemblages. The TEOW framework originally delineated 867 terrestrial ecoregions nested into 14 major biomes, contained with

1650-783: The World, released in 2008, has 426 ecoregions covering virtually the entire non-marine surface of the earth. World Wildlife Fund (WWF) identifies twelve major habitat types of freshwater ecoregions: Large lakes, large river deltas, polar freshwaters, montane freshwaters, temperate coastal rivers, temperate floodplain rivers and wetlands, temperate upland rivers, tropical and subtropical coastal rivers, tropical and subtropical floodplain rivers and wetlands, tropical and subtropical upland rivers, xeric freshwaters and endorheic basins, and oceanic islands. The freshwater major habitat types reflect groupings of ecoregions with similar biological, chemical, and physical characteristics and are roughly equivalent to biomes for terrestrial systems. The Global 200 ,

1705-480: The authors was to support global biodiversity conservation by providing a "fourfold increase in resolution over that of the 198 biotic provinces of Dasmann (1974) and the 193 units of Udvardy (1975)." In 2007, a comparable set of Marine Ecoregions of the World (MEOW) was published, led by M. Spalding, and in 2008 a set of Freshwater Ecoregions of the World (FEOW) was published, led by R. Abell. Bailey's ecoregion concept prioritizes ecological criteria and climate, while

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1760-493: The balance between tectonic subsidence and rates of evaporation and sedimentation. Where the basin floor is dropping more rapidly than water and sediments can accumulate, any lake in the basin will remain below the sill level (the level at which water can find a path out of the basin). Low rainfall or rapid evaporation in the watershed favor this case. In areas where rainfall is higher, riparian erosion will generally carve drainage channels (particularly in times of flood), or cause

1815-408: The basin, eventually making the water saline and also making the basin vulnerable to pollution. Continents vary in their concentration of endorheic regions due to conditions of geography and climate. Australia has the highest percentage of endorheic regions at 21 per cent while North America has the least at five per cent. Approximately 18 per cent of the Earth's land drains to endorheic lakes or seas,

1870-677: The broad latitudinal divisions of polar, temperate, and tropical seas, with subdivisions based on ocean basins (except for the southern hemisphere temperate oceans, which are based on continents). Major marine biogeographic realms, analogous to the eight terrestrial biogeographic realms , represent large regions of the ocean basins: Arctic , Temperate Northern Atlantic , Temperate Northern Pacific , Tropical Atlantic , Western Indo-Pacific , Central Indo-Pacific , Eastern Indo-Pacific , Tropical Eastern Pacific , Temperate South America , Temperate Southern Africa , Temperate Australasia , and Southern Ocean . A similar system of identifying areas of

1925-564: The degree that a lake no longer forms. Even most permanent endorheic lakes change size and shape dramatically over time, often becoming much smaller or breaking into several smaller parts during the dry season. As humans have expanded into previously uninhabitable desert areas, the river systems that feed many endorheic lakes have been altered by the construction of dams and aqueducts. As a result, many endorheic lakes in developed or developing countries have contracted dramatically, resulting in increased salinity, higher concentrations of pollutants, and

1980-401: The delineation of ecoregions an imperfect science. Another complication is that environmental conditions across an ecoregion boundary may change very gradually, e.g. the prairie-forest transition in the midwestern United States, making it difficult to identify an exact dividing boundary. Such transition zones are called ecotones . Ecoregions can be categorized using an algorithmic approach or

2035-440: The disruption of ecosystems. Even within exorheic basins, there can be "non-contributing", low-lying areas that trap runoff and prevent it from contributing to flows downstream during years of average or below-average runoff. In flat river basins, non-contributing areas can be a large fraction of the river basin, e.g. Lake Winnipeg 's basin. A lake may be endorheic during dry years and can overflow its basin during wet years, e.g.,

2090-405: The early 1970s, the term 'ecoregion' was introduced (short for ecological region), and R.G. Bailey published the first comprehensive map of U.S. ecoregions in 1976. The term was used widely in scholarly literature in the 1980s and 1990s, and in 2001 scientists at the U.S. conservation organization World Wildlife Fund (WWF) codified and published the first global-scale map of Terrestrial Ecoregions of

2145-783: The former Tulare Lake . Because the Earth's climate has recently been through a warming and drying phase with the end of the Ice Ages, many endorheic areas such as Death Valley that are now dry deserts were large lakes relatively recently. During the last ice age, the Sahara may have contained lakes larger than any now existing. Climate change coupled with the mismanagement of water in these endorheic regions has led to devastating losses in ecosystem services and toxic surges of pollutants. The desiccation of saline lakes produces fine dust particles that impair agriculture productivity and harm human health. Anthropogenic activity has also caused

2200-501: The land surface of the Earth into eight biogeographical realms containing 867 smaller terrestrial ecoregions (see list ). The WWF effort is a synthesis of many previous efforts to define and classify ecoregions. The eight realms follow the major floral and faunal boundaries, identified by botanists and zoologists, that separate the world's major plant and animal communities. Realm boundaries generally follow continental boundaries, or major barriers to plant and animal distribution, like

2255-422: The largest of these land areas being the interior of Asia. In deserts, water inflow is low and loss to solar evaporation high, drastically reducing the formation of complete drainage systems . In the extreme case, where there is no discernible drainage system, the basin is described as arheic . Closed water flow areas often lead to the concentration of salts and other minerals in the basin. Minerals leached from

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2310-472: The oceans for conservation purposes is the system of large marine ecosystems (LMEs), developed by the US National Oceanic and Atmospheric Administration (NOAA). A freshwater ecoregion is a large area encompassing one or more freshwater systems that contains a distinct assemblage of natural freshwater communities and species. The freshwater species, dynamics, and environmental conditions within

2365-434: The past 50 years. Logging and agriculture in the surrounding watershed have contributed to siltation of the lake (1 cm / year - 1.2 million cubic meters / year), and water diversion for agriculture and urbanization has reduced the size of the lake by 40 square kilometers, and 2.6 meters in depth. Other threats include untreated sewage, the introduction of exotic species, and chemical pollution. In February 2021, members of

2420-430: The probability of encountering different species and communities at any given point remains relatively constant, within an acceptable range of variation (largely undefined at this point). Ecoregions are also known as "ecozones" ("ecological zones"), although that term may also refer to biogeographic realms . Three caveats are appropriate for all bio-geographic mapping approaches. Firstly, no single bio-geographic framework

2475-415: The quality, health, and integrity of ecosystems ". "Characteristics of geographical phenomena" may include geology , physiography , vegetation, climate, hydrology , terrestrial and aquatic fauna , and soils, and may or may not include the impacts of human activity (e.g. land use patterns, vegetation changes). There is significant, but not absolute, spatial correlation among these characteristics, making

2530-599: The surrounding rocks are deposited in the basin, and left behind when the water evaporates. Thus endorheic basins often contain extensive salt pans (also called salt flats, salt lakes, alkali flats , dry lake beds, or playas). These areas tend to be large, flat hardened surfaces and are sometimes used for aviation runways , or land speed record attempts, because of their extensive areas of perfectly level terrain. Both permanent and seasonal endorheic lakes can form in endorheic basins. Some endorheic basins are essentially stable because climate change has reduced precipitation to

2585-408: The term is somewhat vague. It has been used in many contexts: forest classifications (Loucks, 1962), biome classifications (Bailey, 1976, 2014), biogeographic classifications ( WWF / Global 200 scheme of Olson & Dinerstein, 1998), etc. The phrase "ecological region" was widely used throughout the 20th century by biologists and zoologists to define specific geographic areas in research. In

2640-454: The terrestrial ecoregions; only the priority conservation areas are listed. See Global 200 Marine ecoregions for a full list of marine ecoregions. In 2007, TNC and WWF refined and expanded this scheme to provide a system of comprehensive near shore (to 200 meters depth) Marine Ecoregions of the World (MEOW). The 232 individual marine ecoregions are grouped into 62 marine provinces , which in turn group into 12 marine realms , which represent

2695-913: The trees are predominantly conifers ( gymnosperms ), or whether they are predominantly broadleaf ( Angiosperms ) and mixed (broadleaf and conifer). Biome types like Mediterranean forests, woodlands, and scrub ; tundra ; and mangroves host very distinct ecological communities, and are recognized as distinct biome types as well. Marine ecoregions are: "Areas of relatively homogeneous species composition , clearly distinct from adjacent systems….In ecological terms, these are strongly cohesive units, sufficiently large to encompass ecological or life history processes for most sedentary species." They have been defined by The Nature Conservancy (TNC) and World Wildlife Fund (WWF) to aid in conservation activities for marine ecosystems . Forty-three priority marine ecoregions were delineated as part of WWF's Global 200 efforts. The scheme used to designate and classify marine ecoregions

2750-517: The water drainage flows into permanent and seasonal lakes and swamps that equilibrate through evaporation . Endorheic basins are also called closed basins , terminal basins , and internal drainage systems . Endorheic regions contrast with open lakes (exorheic regions), where surface waters eventually drain into the ocean. In general, water basins with subsurface outflows that lead to the ocean are not considered endorheic; but cryptorheic . Endorheic basins constitute local base levels , defining

2805-495: The water level in the terminal lake to rise until it finds an outlet, breaking the enclosed endorheic hydrological system's geographical barrier and opening it to the surrounding terrain. The Black Sea was likely such a lake, having once been an independent hydrological system before the Mediterranean Sea broke through the terrain separating the two. Lake Bonneville was another such lake, overflowing its basin in

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2860-584: The watershed has intensified. Farming and livestock ranching in the basin have significantly increased. Over 10,000 hectares of forest have been lost to logging, fires, fuelwood gathering, and clearance for farming and ranching. The Lake Pátzcuaro basin is home to the Purépecha people . Purépecha leaders established the basin as the heartland of the Tarascan state , which rivaled the Aztec Empire before

2915-488: The watershed surrounding the wetlands, the natural terrestrial vegetation is composed of xeric scrub (1,920-2,100 m above sea level), pine and oak forests intertwined with xeric scrub (2,100-2,400 m) and by pure pine-oak forests in the higher peaks (2,400-2,900 m). The pine-oak forests are part of the Trans-Mexican Volcanic Belt pine-oak forests ecoregion . In the last fifty years, human activity in

2970-412: The wetlands, including some endemic species such as the black-polled yellowthroat ( Geothlypis speciosa ). Two native species have not been observed recently; the yellow rail (Coturnicops noveboracensis) has not been seen since 1964 and may be locally extinct, and the endemic slender-billed grackle ( Quiscalus palustris ) is presumed extinct. The Lake Pátzcuaro salamander ( Ambystoma dumerilii )

3025-491: The world's 8 major biogeographical realms. Subsequent regional papers by the co-authors covering Africa, Indo-Pacific, and Latin America differentiate between ecoregions and bioregions, referring to the latter as "geographic clusters of ecoregions that may span several habitat types, but have strong biogeographic affinities, particularly at taxonomic levels higher than the species level (genus, family)". The specific goal of

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