Marismas Nacionales is located in the north-western Pacific coast of Mexico and contains a large complex of brine coastal lagoons, mangroves, muddy bogs or swamps, and ravines. It encompasses the regions known as Las Cabras, Teacapán, Agua Brava, Marismas Nacionales and San Blas. The Marismas are fed by seven rivers and alternate streams such as the Baluarte, Cañas, Acaponeta, San Pedro, Bejuco, Santiago and San Blas or Sauta rivers. The area spans the south coast of Sinaloaand the north coast of Nayarit, and connects to the Pacific Ocean through the Bocas de Tecapán, Cuautla, El Colorado and the Santiagoand San Pedro River deltas.
This region comprises 279,000 acres (113, 000 hectares) of mangroves and estuaries (15-20% of the country’s total mangrove forests and the most extent of its type in the pacific coast), small patches of timber-yielding tropical forest (cedars, oaks, amapas, among others), non timber-yielding forest (oil palm, coconut palm, and white, red, black and Chinese mangrove) and pastures.
Currently, three proposals have been submitted to the National Commission of Protected Natural Areas (CONANP) in order to register the following as natural protected areas: Singayta-La Tovara-Los Negros system in San Blas under the Flora and Fauna Protection category; Teacapan, Agua Brava, and Marismas Nacionales system under the Biosphere Reserve category; and Guisache-Caimanero-Las Cabras system also under the Biosphere Reserve category.
The area hosts 14 species of native flora that are at risk (endemic, threatened, and/or extinction risk). Additionally, it also hosts 99 endemic fauna species (including mammals, birds, reptile, and amphibians), and 73 species threatened or endangered of extinction.
The site holds a population of 446 avian species, 38 of them are shorebirds. Counts performed in 1994 recorded 206,000 individuals, with Recurvirostra americana being the more abundant with nearly 61,000 individuals. During more recent censuses, 46,234 individuals of this species have been recorded. The area is also breeding ground for Charadius wilsonia, Charadrius alexandrinus, and Himantopus mexicanus.
Fishery, agriculture, cattle ranching, shrimp farming, and tourism (the latter in the developing stage), are the main economic activities in the site. Agriculture constitutes the major portion of the primary revenue. Major employment is generated by the communal, personal, and social services provided.
Construction of dams, roads, and shrimp pond dikes, as well as the opening of the Cuatla Channel, are deeply modifying the site ecosystem.
In recent years, projects aimed at the site’s conservation have been carried out, such as Linking Communities, Wetlands, and Migratory Birds that joins three Western Hemisphere Shorebird Reserve Network (WHSRN) sites in North America: Marismas Nacionalesin Mexico, Great Salt Lake in Utah (U.S.A.), and the Chaplin and Quill Lakes in Saskatchewan, Canada. Each site holds large populations of migratory shorebirds. Additionally, the San BlasInternational Festival of Migratory Birds, that took place in 2007, joined the Great Salt Lake and Chaplin Lake Festivals by also selecting the Marbled Godwit (Limosa canela fedoa) as the commemorative bird.
Geographic, Climatic and Physical features
The more abundant geological forms are sedimentary volcanic rocks from the Cenozoic period and recent alluvial deposits. Soils show an accumulation of soluble salts with high sodium content. There are also corrosive soils, with diverse salt or sodium contents, which affect construction materials in direct contact with them differently. According to the geo-morphological classification of the coasts, the region presents accumulative coasts (marsh) with flood plains, mangrove and/or marine swamps. Towards the north are accumulative coasts (of low sandy beaches) and coastal lines (ancient beaches lines).
Climate of the region corresponds to the semi-warm sub-humid Aw1(h’), with an annual mean temperature of 26 to 28ºC, and a highest annual mean temperature of 30 to 34ºC. Total annual precipitation varies from 300 to 1,000 mm; and from 800 to 1,200 mm with an annual relative humidity over 75% and a total annual evaporation of 1,800 to 2,000 mm. The coastal plain corresponds with the low Gulfof California Mareographic Region, characterized by a mixed tide type, predominantly semidiurnal.
In the coastal plain there are many inland waters or reservoirs, which give the area its name – Nayarit estuarine zone. These lakes, formed basically by marshes and the drains from various rivers and streams, covers an area of 920 km2.
This plain is crossed by numerous rivers and streams that originate in the western Sierra Madre and flow into the various lakes or in the Pacific Ocean. These rivers form fertile valleys, where the human settlements have concentrated. Every tributary of Nayaritbelongs to the Pacific Ocean slope, such as Acaponeta, San Pedro Mezquital, and Huaynamota, which is a tributary of the SantiagoRiver. They all originate in the State of Durango and form deep canyons in their middle basins. Main rivers that cross the region from north to south are: Baluarte, Cañas, Acaponeta, San Francisco, Rosamorada, Bejuco, San Pedro, Río Grande de Santiago, and San Blas or Sauta.
Water and Vegetation
Nayaritcoastal lakes exhibit estuarine conditions of high permanence; the mix of marine and fresh waters generates the most productive ponds in the northwest. They support important lake and deep ocean fisheries. Small ponds are ecosystems of high productivity and constitute an important corridor for migratory bird species and a refuge of species threatened with extinction.
Nayaritmangroves are the larger in the Mexican Pacific coast, particularly those of the Teacapán-Agua Brava / Marismas Nacionales-San Blas system. Those are the most productive ecosystems. However, large portions have been disturbed by economic activities. In general, vegetation cover is formed by a tropical savanna, swamp, palm grove, subperennifolia medium jungle, induced grassland that arises spontaneously when the original vegetation is extirpated, halophyte and aquatic vegetation. Coastal dunes vegetation is dominated by creeping plants such as Ipomoea prescaprae.
Mangrove is characteristic from tidelands shores, river mouths and other coastal bodies of water. It grows in alluvial soils periodically flooded by brackish to brine waters. This type of vegetation lacks herbaceous elements and is dominated by Laguncularia racemosa, Rhizophora mangle, Avicenia germinans, and Conocapus erectus. Mangrove trees form dense forests, which reach 25m of height. Other prominent species are the Ciruelillo (Phyllanthus elsiae), zapotón(Pachira acuatica), and the anona(Anona glabra).
The palm groves or Orbignya's forest appears in disturbed sites, near the coastline, over deep and well-drained sands. The dominant species is Orbignya guacoyule, though other species like Ficus sp., are sporadically present. Halophyte vegetation is located along the coast, below 10 m.a.s.l., on plain areas exposed to marine floods, where salt is highly concentrated in ponds with slow drainage. More common halophyte plants species are Salicornia spp., Batis spp., Sesuvium portulacastrum, Suaeda brevifolia, S. ramosissima, Salicornia europaea.
Nowadays the diverse fauna is classified as Neotropical and presents a considerable number of species that are endemic, migratory, threatened with extinction, and of economic importance. The diversity of the fauna is associated with the environmental heterogeneity of the zone. In Sinaloa and Nayarit, 543 species of vertebrates have been reported, including 51 endemics. At least 60 species are threatened with extinction, particularly due to habitat overexploitation and destruction. Among the relevant species are jaguar (Panthera onca), river crocodile (Crocodylus acutus), Lilac-crowned Parrot (Amazona finchii), and Green Macaw (Ara militaris).
A total of 98 mammal species (22 % of the country’s total) have been recorded in the region. At least 12 species are endemic to Mexico and 9 (10 % of the total) are threatened with extinction. Among these are the river otter (Lutra canadiensis), the wild boar or pecarí (Tayassu tajacu), puma (Puma concolor), jaguar (Panthera onca), wildcat (Linx rufus), ocelot (Leopardus pardalis), margay(Leopardus wiedii) and white-tail deer (Odocoileus virginianus).
Reptile and amphibian species are diverse and the majority exhibits specific habitat requirements. There are at least 9 endemic species and 13 threatened with extinction. Among the threatened species recognized by the Official Mexican Regulation (NOM-059-SEMARNAT-2001), that provides protection to the wild, native flora and fauna species, are the scorpion (Heloderma horridum), green iguana (Iguana iguana), river crocodile (Crocodylus acutus), and four species of sea turtles (Prieta: Chelonia mydas, Laud: Dermochelys coriacea, Carey: Eretmochelys imbricata, y Golfina: Lepidochelys olivacea). The region’s poisonous species include the scorpion, rattlesnake (Crotalus basiliscus and C. atrox), cantil (Akistrodon bilineatus), coralillo (Micrurus distans), and sea snake (Pelamys platurus).
A total of 446 bird species have been recorded in the area, which represents 44% of the total Mexican avifauna. Bird species in the zone that are considered a priority by the North American Wetlands Conservation Act include: 83% of waterfowl species, 41% of shorebirds, 66% of congregatory waterbirds, 71% of marsh birds, and 5% of land birds. Up to 4.5% of the Mexican waterfowl species and 20% of the global population of avocets (Recurvirostra americana) use this ecosystem. This, along with the high number of resident and endemic bird species here, have lead the North America Bird Conservation Initiative (NABCI) to identify it as one of the 5 pilot sites for bird conservation at a continental scale, based on a strategy aimed at the development of a Regional Conservation Alliance for birds and their habitat.
The site plays an important role for both resident and migratory avifauna. Several species of ornithological importance are record in the area, such as: Anas americana; A. platyrhynchos; A. acuta; A. discors, A. cyanoptera; Aythya affinis; Egretta caerulea; E. tricolor; Mycteria americana; Charadrius melodus, Numenius americanus; Limosa fedoa; Calidris alba; C. mauri; Sterna nilotica; S. antillarum; and Rynchops niger, among others. In January 1992, an aerial census performed by Brian Harrington counted 24,746 shorebirds in the site. He estimated a total of 110,000 shorebirds, where the main species were:
American avocet 61,527
Small Shorebirds 18,980
Medium-sized shorebirds (mainly Short-billed Dowitcher) 17,680
Large-sized shorebirds (mainly Godwits and Willet) 3,948
Beside Morrison’s research (1994), there are no other shorebirds census studies at the site. Only SEMARNAT has been monitoring species presence in specific sites during the last 6 years, observing a very low population decrement, and the presence of species that had changed their migratory path. However, these studies are not based on a scientifically designed methodology. Therefore in 2007, six Biology students from the Universidad Autónoma de Nayaritwere trained and initiated a census of shorebird and waterbird populations.
The area forms part of the Hydrological Basin of the Santiago River, where three hydroelectric dams (HD) were built: AguamilpaHD, El Cajón HD, and Santa Rosa HD. Between the last two, the construction of La Yesca HD has already began, causing important hydrodynamic changes on the lower basin. Feasibility studies for the construction of a hydroelectric dam on the San Pedro River had begun, performed by the Federal Commission for Electricity.
On the other hand, the construction of extensive aquaculture farms have increased, generated by both national and international pressures, which entails the creation of dikes in regions of slight slope, such as coastal plains. This has originated changes in the hydrological pattern due to the detour of the superficial runoffs of fresh water. These changes prevent the runoffs to cross through flooded areas, such as marshes and mangroves, causing floods in the lower zones of the coastal plain (usually agricultural zones or lowland jungle ecosystems), or increasing the water permanence period in marshes and mangroves. Dikes also prevent tides to cross through these areas, causing relatively high mangrove mortality. In the case of La Tovarazone, in the San BlasMunicipality, the environmental impact on mangroves is remarkable. The area suffers from severe forest logging and clearing to establish mango, avocado andbanana orchards, as well as the expansion of the agriculture frontier for bean, corn, and vegetable crops, and creation of grassland for extensive cattle ranching. These activities have produced erosion, with the consequent sedimentation of stream and lakes, and springs disappearance. All these body-waters are important for the arrival of both migratory and breeding species.
Additionally, two channels that allow the direct inflow of sea water were opened in the region. One has almost 3.5 km length and nearly 1 kilometer width, to the south of the Ejido Palmarde Cuautla; the other, more recently created, is 15 m wide and 5 km long, located to the north of the San Pedroriver. Through the channels’ route there have been installed “Tapos,” wood traps for larvae and shrimp retention.
In Nayarit, there have been attempts to control predators,mainly during the early development of aquaculture activities. Occasionally, poisons such as cyanide, rotenone (for fish control), and plants derivates – such as San Juanicoseeds (castor-oil plant), have been erroneously used for this purpose. Fishermen from Agua Bravaclaim that massive fish mortality in 1983 (vox populi) was due to the use of these toxics. Similarly, in the shrimp-farms, culling of resident and migratory birds is performed without control and often indiscriminately, which is demonstrated by the elimination of species considered threatened with extinction or protected by law, such as the Osprey (Pandion haliaetus), the Pacific Great Blue Heron (Ardea herodias), the geese species (Anser albifrons, Branta canadensis, and Chen caerulensis), and the Sandhill Crane (Grus canadensis). Due to habitat modification, winter populations of these species have decreased at the site up to 90%. On the other hand, the establishment of limited hunting grounds and the use of firearms could cause lead accumulation in the ponds’ sediments, with the risk of increasing its concentration in the water and being incorporated to the food chain, including shrimp, with the known consequences.
Another factor provoking mangrove loss is road construction, like the NovillerotoPericosfishing field roadand the one from Union de Corrientes to Santa Cruz, which both prevented the tides to cross through mangrove zones. This disturbance provoked the forest to loss its structure transforming it into marshes with dispersed mangrove bushes, in an extension of approximately 6,170 acres in the first case, and of 247 acres in the second case. Despite some restoration works, the disturbance effect is still ongoing on.
In the sub-humid Nayaritregions, construction of dikes, roads, and minor roads, can increase the permanence period of fresh water in marshes zones, replacing these ecosystems for fresh water swamps. Distribution of the different mangroves species is mainly related with day-flood periods of each specific area. When these periods increase or decrease, due to either human influence or natural causes, mangrove goes through a succession process or die, in extreme cases.
The Linking Communities, Wetlands and Migratory Birds project, lead by Wetlands International and the SEMARNAT Federal Delegation in Nayarit, is an initiative that links three North American sites that are part of the Western Hemisphere Shorebird Reserve Network (WHSRN). The sites support migratory shorebird populations through their migration from Canada to Mexico, and include the Marismas Nacionales in Mexico, Great Salt Lake in Utah, and Chaplin and Quill lakes in Saskatchewan, Canada. The project links sites through Environmental Education, implementing the program “Shorebird Sister Schools” (Escuelas Hermanas para las Aves Playeras).
Additionally, this effort fosters conservation through the development of the Strategic Plan for Sustainable Development and the Regional Alliance, given that this area is one of the pilot sites for the NABCI Regional Alliances establishment. The Alliance is aimed at birds and habitat conservation, and community participation through tourism. Ecotourism will be an important support for the local communities and will ensure the long-term habitat conservation, as well as education for youngsters from the area regarding migrant birds. Currently, participating communities include San Blas, Pimientillo, Palma Grande, Murillos, and Mexcaltitàn. As a part of these actions, the International Festival of the Migratory Birds was established. It is expected to contribute to the massive conservation of migratory birds’ habitat in the hemisphere, through activities that are compatible with improvement of local livelihoods and environment protection.
As a part of the Project Linking Communities, Wetlands and Migratory Birds an exchange program between the Weber University in Ogden, Utah (USA) and the Universidad Autónoma de Nayarit (Mexico) was established in order to train students and to develop shorebird research projects.
In January 2008, derived from an agreement between SEMARNAT and the Peace Corps program, two scientists are supporting the site’s conservation program.
Secretary of Environment and Natural Resources
University of Nayarit
International Migratory Bird Festival of San Blas, Nayarit
Friends of Great Salt Lake
National Commission for Knowledge and Use of Biodiversity
Carlos Villar Rodríguez
Federal Delegation of SEMARNAT in Nayarit
011-52 (311) 215-4930