Central Mexican wetlands
The Central Mexican wetlands, located within the hydrological basin of the Lerma and Santiago Rivers, are a unique ecoregion characterized by a rich diversity of endemic species and vital habitats for both resident and migratory birds. This region encompasses several states in Central Mexico and is notable for its fragmented lakes, such as Lake Chapala and Lake Cuitzeo, which were formed by ancient volcanic activity. The wetlands support a variety of plant species, including cattails and Montezuma cypress, as well as approximately 100 native fish species, many of which are endemic. However, these wetlands face significant threats from human activities, including water extraction, pollution, and invasive species, which have led to habitat degradation and the decline of native wildlife. Conservation efforts are underway to protect and restore these vital ecosystems, with several areas designated as protected sites under national and international frameworks. The wetlands also play a critical role in providing ecosystem services, supporting local livelihoods, and serving as sites of cultural significance, particularly for indigenous communities. Despite the challenges they face, the Central Mexican wetlands remain essential for biodiversity and ecological health in the region.
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Subject Terms
Central Mexican wetlands
- Category: Inland Aquatic Biomes.
- Geographic Location: Central America.
- Summary: Home to an exceptional number of endemic species and an important refuge for overwintering migratory birds, these wetlands are threatened by water extraction, buildup of sediment and salt, contamination, and invasive species.
Ancient volcanic activity in the center of Mexico fragmented the watershed of the Lerma and Santiago Rivers, resulting in the formation of many isolated lakes and wetlands. This isolated nature gave rise to an exceptionally high number of species that are unique to the ecoregion. These wetlands are also an important habitat for resident and migratory birds. The ecoregion is threatened by overextraction of water, pollution, and invasive species. Several sites within the Central Mexican wetlands have been designated as protected areas, and efforts are under way to conserve this important ecoregion.
The Central Mexican wetlands are associated with the many lakes in the hydrological basin of the Lerma and Santiago Rivers. This basin includes portions of the Central Mexican states of Guanajuato, Hidalgo, Jalisco, Michoacán, Morelos, Puebla, Queretaro, Tlaxcala, Veracruz, and the Federal District. It is located in the Trans-Mexican Volcanic Belt, a mountainous region that crosses the center of Mexico. Geological and biological evidence indicates that the basin was originally an open, interconnected hydrologic system, but volcanic activity in the Pleistocene fragmented the basin, resulting in the formation of many isolated, endorheic lakes (lakes that do not drain into the ocean).
The majority of Mexico’s natural lakes are found in this area, including Chapala and Cuitzeo, the country’s two largest lakes. Lake Chapala is also the third-largest lake in Latin America, and the second-highest in the Americas.
Biota
The vegetation of the wetlands is characterized by cattails (Typha angustifolia, T. dominguensis, and T. latifolia), bulrushes (Scirpus spp.), arrowheads (Sagitaria spp.), black flatsedge (Cyperus niger), and willow (Salix bonplandiana), as well as floating plants, such as water lilies (Nymphoides spp.), pondweed (Potamogeton spp.), duckweeds, bogmat (Wolffiella lingulata), and water milfoil (Myriophyllum spp.). Mexico’s national tree, the Montezuma cypress (Taxodium mucronatum), also grows along rivers and in marshes in the Central Mexican wetlands biome. Endemic (not found elsewhere) plants associated with the area include Arenaria bourgaei, Panicum sucosum, and Sagittaria macrophylla.
Approximately 100 species of fish are native to this ecoregion, 70 percent of which are endemic. Many of them depend on the wetlands at one or more life stages. Fish families with species and whole genera that are endemic to the Central Mexican Wetlands biome include the neotropical silversides (Atherinopsidae), sucker fish (Castotomidae), chubs and shiners (Cyprinidae), splitfins (Goodeidae), catfish (Istaluridae), and lampreys (Petromyzontidae). The wetlands are also home to endemic or near-endemic species of mollusks, crustaceans, and amphibians. The endemic frogs Lithobates megapoda and L. neovolcanica are threatened species, and the salamander Ambystoma dumerilii is critically endangered.
The Central Mexican wetlands are an extremely important habitat for some 200 species of resident and migratory birds. During the winter months, hundreds of thousands of migratory waterfowl seek refuge, feed, hibernate, and breed here. The endemic black-polled yellowthroat (Geothlypis speciosa) is a globally endangered species. Two other endemic bird species, the yellow rail (Coturnicops noveboracensis) and slender-billed grackle (Quiscalus palustris), have not been observed recently; they are likely extinct. Approximately 40 species of mammals, including threatened ones such as the Mexican long-tongued bat (Choeronycteris mexicana), can be found in the wetlands.
Threats and Conservation
The areas surrounding the Central Mexican Wetlands biome support large populations of people, including some major urban areas. The wetlands provide critical ecosystem services, such as water treatment and aquifer replenishment. Many people depend directly on the wetlands for their livelihoods through fishing, aquaculture, and the manufacture of crafts. The wetlands also serve as a natural buffer from extreme weather events, which can help stabilize the region.
Sites of archeological and cultural significance are also associated with the wetlands. The area surrounding Lake Patzcuaro is home to the P’urhépecha indigenous group; each November, Day of the Dead celebrations are held on the shores and islands of Lake Patzcuaro, attracting tourists from around the world.
The wetlands have been highly affected by human activity. The water that feeds the wetlands is used intensively to support cities and for irrigation, power generation, and transportation. Due to diversion and overextraction of water, much of the marshes and bogs are now dry for much of the year.
Soil erosion associated with severe deforestation, agriculture, and other land clearing activity has caused sediment and salts to build up in water. Water in the wetlands is also contaminated with agricultural chemicals, pollutants from industrial areas, untreated wastewater, and solid wastes. Many native species are at risk of overexploitation. Some invasive species are displacing native species, such as the whitefish Chirostoma estor.
Climate change impacts in this area include higher average temperatures, which have increased the evaporation rate of water in the wetlands. Increases in the frequency and severity of tropical storms have also affected the region, bringing the threat of erosion problems and increased siltation and other stresses to wildlife.
Parts of the Central Mexican wetlands biome are protected, and some conservation activities are under way. Lago de Camécuaro is a national park; the Lerma marshes are protected at the national level as a nature reserve for flora and fauna, and internationally under the Ramsar Convention on wetlands. Other locations that are targeted under the Ramsar Convention include Lake Chapala, the Zapotlán and Sayula lagoons, and the wetlands of Lake Patzcuaro. There are plans to recover populations of some native species and to improve water management.
Bibliography
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