Sumidero Canyon

Geology The Sumidero Canyon was formed by cracks in the Earth's crust along with erosion by the Grijalva River, which still flows through it. The process of its formation began about 35 million years ago, making the Sumidero contemporary with the Grand Canyon on the Colorado River. In addition to the Grijalva, there are other flows of water in the area in and around the canyon, many of which are seasonal. These consist of streams, some of which form waterfalls on the canyon's sides, and underground movements which have created caves and karst formations. These walls expose a long process of disturbance in the Earth's crust with layers of limestone from the Upper Mesozoic, which contain fossils of marine creatures. During the Mesocretac Period, there was an elevation of ocean floor which formed much of the mountains of the area. and the American crocodile, which can be seen on the riverbanks. In another small cave, there is a stalactite called the Caballito de Mar or "Seahorse" after its shape. Climate Despite its biological, ecological and cultural diversity, there have been few studies performed in the park area. For this reason, there is a lack of information about species, habitats and water flow. There is also relatively little information about how human activities affect the park. As the park is located in the Central Valley of Chiapas and borders the Northern Mountains region, altitudes vary from approximately above sea level in the municipality of Chiapa de Corzo to above sea level at the El Roblar lookout point. This geography produces a channel for air flow from northwest to southeast as well as three main climates based on the Köppen system as modified for Mexico. These are hot and dry (where airflow is blocked), semi-hot and humid, and hot and humid. The average rainfall for the park is about 1,000 mm during the rainy season from May to October and 200 mm during the dry season from November to April. Average annual temperature is 26 °C. The rugged terrain also forms a number of microclimates. Vegetation Most of the park's vegetation, especially around the canyon, is dense tropical rainforest. Most species found in the park are members of the family Fabaceae with 59 species and the family Asteraceae with 25 species, which reflect the abundance of these families statewide. Other important families include the Orchidaceae and Euphorbiaceae, each with 22 species, the family Convolvulaceae with 17 species, and the Cactaceae with 11 species. 122 species are considered valuable as ornamental plants with 46 having medicinal uses and 31 species valuable for logging. These mostly come from the rainforest areas. The rainforest vegetation is mostly deciduous, shedding leaves in the dry season. However, there are perennial rainforests, forests of pine and oak, grasslands (mostly induced) and areas with secondary vegetation. The three main vegetation classifications are low-height rainforest, medium-height rainforest (as per the size of the trees), pine-oak forest and meadows. Medium-height deciduous rainforest is mostly located on either side of the canyon, in the north and east of the part towards San Fernando and in the Cañada Muñiz at altitudes of between 150 and 1250 masl. It is mostly found in areas with basalt or granite rock and where there are lime deposits, covering an area of in total. While many plants here loose leaves in the dry season, there are some that retain them year-round. Maximum height of trees varies between 25 and 30 meters. The density of the tree cover in these areas is enough to lower temperatures on the ground in the summer rainy season due to the maximum foliage which occurs at this time. The tree cover is composed of the following species: breadnut (Brosimum alicastrum), guanacaste (Enterolobium cyclocarpum), totoposte (Microdesmia arborea), jocotillo (Astronium graveolens), cedar (Cedrela odorata), cuaulote blanco (Luehea candida), hormiguillo (Platymiscium dimorphandrum), chicozapote (Manilkara zapota), tempisque (Sideroxylon capiri) and various types of amate fig trees (Ficus spp.). Under the tree cover, there is significant plant diversity, including palms and araceas. Epiphytes (air plants) are abundant as well, along with orchids, Bromeliaceae and cactus. Cactus are primarily found on the vertical walls of the canyon and belong to the Acanthocereus family. In the 1970s, tree area in a good state of conservation amounted to , or 17.72% of the total land area. From 1988 to 1993, this amount was reduced to , or 5.35%. From 1990 to 2000, it is estimated that eight percent of the remaining forests and 38% of the rainforests were damaged. Many of the areas in good condition are broken up by disturbed areas. Most of the damage is due to illegal logging and the clearing of land for pasture or agriculture. Medium-height perennial rainforest (also known as evergreen cloud forest) exists only in small dispersed patches, mostly on the sides of the canyon in contact with the Grijalva River. Many of these patches are less than one hectare in size, as they are located on small areas of flat land at altitudes between 1000 and 2,500 masl. The soils are rich in undecomposed plant matter which holds in moisture. Low-height deciduous rainforest is mostly found around the La Ceiba and La Coyota lookout points in the south and southeast sections of the park, with some in the east towards the La Chacona Cañada. These occupy a territory of in the park. Tree heights extend from four to ten meters with some as high as 15 meters. Non-tree species are not as common and mostly consist of succulent species such as Agave, Opuntia, Stenocereus and Cephalocereus. Other important species include Alvaradoa amorphoides, Bursera simaruba, Ceiba aesculifolia, Bursera bipinnata, Bursera excelsa, Cochlospermum vitifolium, Haematoxylum brasiletto, Piscidia piscipula, Swietenia humilis, Acacia collinsii and Pseudobombax ellipticum. Pine–oak forests exist in the northwest of the park in the highest altitudes, covering about . They are part of the same type of forest found in the Soyaló region it is adjacent to. They are found at an altitude of 1,200 masl and above in areas that receive precipitation of about 1500 mm annually. The most common species is the oak Quercus acutifolia (syn. Quercus conspersa), often found mixed with the two kinds of rainforest found in the park. Air plants are common here as well as bromeliads, orchids and plants from the Maxillaria, Lycaste, Cattleya and Laelia groups. Grassland is not naturally occurring but rather exists due to human activities such as farming and livestock raising. It is seen on the north and south sides of the canyon and is usually associated with secondary vegetation such as Tecoma stans, Gliricidia sepium, Plumeria rubra and Acacia collinsii, occupying an area of in the park. Wildlife Throughout the history of the area, especially since it was definitively explored in the 1960s, the area's wildlife diversity has been severely negatively impacted by human encroachment in the form of settlements, agriculture and hunting. However, since the federal park was established in the 1980s, wildlife diversity has increased. In 1986, the federal Secretaría de Agricultura y Recursos Hidráulicos (SARH) reported a total of ninety species of vertebrates divided into four species of fish, one amphibian, 14 reptiles, 26 birds and 40 mammals. A 2005 study indicates 308 species with four species of fish, 15 amphibians, 195 birds, and 53 mammals. Between these two, there have been a number of other studies which also show the growth of the number of wildlife species in the park. Information about fish species is scarce but at least four protected species have been detected. According to a CONANP study in 2007, there are 12 species of reptile here under protection, including the river crocodile (Crocodylus acutus), and one threatened species, the Yucatán banded gecko (Coleonyx elegans). Birds are the most common type of animal in the park, with about 195 species documented. Six of these species are threatened and 17 are subject to special protection. One threatened bird species in the park is the great curassow (Crax rubra). Relatively abundant species include Actitis macularia, Dendrocygna autumnalis, Egretta caerulea, Egretta thula, Tachybaptus dominicus and Coragyps atratus, all of which are associated with bodies of water. There have been 53 species of mammals detected recently in the park, of which two are considered threatened, two in danger and two subject to special protection. Endangered and threatened species include the spider monkey (Ateles geoffroyi), jaguarundi, ocelot, lowland paca, white-tailed deer, anteater (Tamandua tetradactyla) and king vulture (Sarcoramphus papa). The most abundant species include the bat Artibeus jamaicensis and the rat Peromyscus mexicanus. ==National park==

Establishment of the park The Sumidero Canyon National Park has its origins in a Chiapas state decree issued in 1972, which made the area around the canyon an ecological reserve to preserve its geology, history and wildlife and to allow for scientific study. The center of the park is the Sumidero Canyon and the Grijalva River that runs from south to north through it. The park's borders on this river are marked by the Belisario Domínguez Bridge, over which the Pan-American Highway runs, in the south and the Chicoasén Dam, to the north. The park is divided into four sections by direction: the northwest includes medium-height, somewhat deciduous rainforest as well as some lowland rainforest and grassland, found in the municipalities of Osumacinta and San Fernando; the western section has similar vegetation, and is located entirely in San Fernando; the eastern section has forests of pine as well as medium-height semi-deciduous rainforest and grasslands, and is found in Chiapa de Corzo; and the southeast has most of the sides of the canyon itself and a navigable section of the Grijalva River, but only remnants of medium-height rainforest and pachycaulous vegetation. The main land access into the park is from Tuxtla Gutiérrez north through Osumacinta then past the Chicoasén Dam. Another access point is from Chiapa de Corzo by boat from the Cahuaré Docks. As the main attraction of the park is the canyon, several lookout points have been constructed on various parts of the rim. La Ceiba is closest to the city of Tuxtla Gutiérrez, only away. The Los Chiapas point is near where the canyon's walls rise highest from the river below, where according to legend, a number of Chiapa people preferred to commit suicide by jumping rather than submit to Spanish domination. This lookout also has a restaurant. ==Conservation issues==

The most important conservation issue in the park is the contamination of the Grijalva River, which passes through the Sumidero Canyon proper. Most of these illegal constructions belong to the very poor who have migrated to the city from elsewhere. The demand for living space has created an industry of illegal subdivisions which are then sold without the proper title to victims. Three of the main neighborhoods to develop in this way are the Patria Nueva Alta, Arroyo Blanco, La Esperanza and Las Granjas. The encroachment is a result of the fast population growth of Tuxtla Gutiérrez and Chiapa de Corzo. The growth of these areas has led to land ownership disputes, loss of wild habitat and deforestation. In 2002, the federal and state government signed an accord to remove illegal human settlements and work to prevent further encroachment. Much of the sewage comes into the Grijalva via the Sabinal River, which carries most of the waste water of the city of Tuxtla Gutiérrez. In addition, trash and raw sewage makes its way into the river from the various tributary streams. The most obvious pollution is garbage, especially plastic containers, which mostly comes from area homes and businesses tossed onto the ground or in streams, especially from Chiapa de Corzo and Tuxtla Gutiérrez due to the lack of environmental awareness according to Conanp. The quantity of this trash reaches its height during the rainy season, when runoff and swollen streams can carry more of it into the Grijalva. Somewhere between 80 and 90% of the waste solids found in the river is branches, wood, rocks, sediment and other debris from legal and illegal logging, which cause deforestation . These mostly come into the river during the rainy season, especially from the Villa Flores and Villa Corzo municipalities. As the solids flow along the Grijalva, they are constricted by the narrow channel of the canyon and then by the presence of the Chicoasén Dam. There are year-round and seasonal efforts to clean the river within the canyon and the area just upstream from it. Much of the daily effort is undertaken by workers with the Comisión Nacional de Áreas Naturales Protegidas (CONANP) and the Secretariat of Tourism in Chiapas, which extract twelve tons of garbage from the Grijalva river each day. Efforts can involve up to 600 people at a time using 32 boats from four of the tourist cooperatives. During the annual campaign to clean the canyon in 2005 more than 60,000 tons of trash was removed. Generally, about forty tons of garbage is collected each day during these campaigns. While the cleanup efforts have improved the situation in the canyon, the garbage reaccumulates especially during the rainy season. Part of the price that tourists pay for boat rides into the canyon pays for cleanup efforts, but the boat operators state that the canyon remains filled with trash. Conanp also states that cleanup efforts are insufficient. Mexico's federal environmental agency, the Secretaría de Medio Ambiente y Recursos Naturales (Semarnat) states that it cannot get involved in the situation as it is the municipalities that have the responsibility for disposing of trash appropriately. However, many of these local governments do not have landfills or the separation of recyclables. ==Tourism==

The scenery of the canyon has become a major tourist attraction for the state, with developments for eco tourism and extreme sports. The navigable part of the Grijalva River is mostly used to ferry visitors into the canyon area. The park has six lookout points accessible by land called La Ceiba, La Coyota, El Roblar, Tepehuaje, Los Chiapas and Manos. In the rainy season, tourism is enhanced by the activity of waterfalls such as the Árbol de Navidad, Cueva del Hombre, Cueva del Silencio, Cueva de Colón, Cueva de Colores and Cueva del Suspiro. A lesser known attraction is the archeological site called the Ruins of Berlin. The most important economic activity in the canyon is ecotourism. Most of the visitors are Mexicans. Weekends are busiest with local and regional visitors to bike, swim, hike, camp and picnic. As they take visitors from Chiapa de Corzo or Tuxtla Gutiérrez through the canyon and to the dam, they provide environmental, historical and cultural information. These are the most organized tourist activities in the park. For those who choose to see the canyon from the lookout points above, there are restaurants and other food service places as well as camping and picnicking facilities. Extreme sports include mountain biking, rappelling, spelunking and more. Rappelling allows for access to many of the canyon's small caves which are not accessible any other way. ==Chicoasén Dam==

At the northern end of the Sumidero Canyon is the Chicoasén Dam, formally called the Manuel M. Torres Dam, is one of a number of dams which have been built along the Grijalva River for water storage and the generation of hydroelectric power. This dam and its reservoir is considered to be part of the Sumidero Canyon system. The Sumidero Canyon National Park is defined on the north end of the river by this dam and the Belisario Domínguez Bridge on the south. The dam was constructed between 1974 and 1980. The reservoir covers an average of 2,193 hectares, and the complex employs about 600 workers. The Chicoasén Dam produces electricity and manages the flow of the Grijalva river along with the Hondo River and the Muñiz, El Jardín and El Cacao streams, which converge to form the Osumacinta River. This reservoir is one of the most important in the country. The hydroelectric station is also one of the most important in the country with thirty generators with installed capacity of 3,928.48 megawatts. This is just over thirty percent of all hydroelectric energy produced in Mexico. ==History and archaeology of the area==

The history of the area is connected to the Chiapa people, who occupied the Central Valley area before the arrival of the Spanish. The origin of these people is not known, but theories have them migrating north from Nicaragua or even Paraguay. Their main settlement was in Chiapa de Corzo near the canyon, with a fortified area in the higher areas in the canyon for protection from invasions. The Chiapa fiercely resisted Spanish conquest and were not subdued until the arrival of Diego de Mazariegos in 1528. Their last refuge was in the fortified area, now known as the archeological site of the Ruins of Berlin. Here the last of the Chiapa held out from 1528 to 1535 after the Spanish took over the main city. Legend states that when this last fortification fell, the remaining Chiapa committed collective suicide by jumping into the canyon. Since then, the canyon has served as a boundary marker between the Zoque and Tzotzil peoples. Until the 20th century, the canyon area was relatively unexplored. In 1895, three Frenchmen attempted to explore the canyon but were drowned in the river. An American came in 1932 but also perished. This gave rise to legends about witchcraft in the areas as well as the ferocity of the area's crocodiles. In 1960, an expedition of soldiers from the Mexican army, nicknamed the "red handkerchiefs" succeeded into crossing through the canyon by boat over twenty km. This opened up the canyon to local exploration and exploitation, including rudimentary tourism and the hunting of crocodiles and other native fauna. There has been little archaeological work done in the area. The main site is called the Ruins of Berlin, named after German explorer Heinrich Berlin, who visited the area in 1946 and named the area "Sumidero". This site is located seven km from the Belisario Domínguez Bridge in Tuxtla on the edge of the river. It covers an area of 467 by 60 meters, bounded by small mounds surrounding patios. The original description of the site was undertaken in 1923 and 1932 by Becerra, who called it Chiapa Viejo, and stated it was the capital of the Chiapa people. However, Remesal in 1966 determined it was a secondary site. The last major survey was done in 1976 by Alejandro Martínez, discovering that there are 24 individual sites of which nine are mounds and fifteen are in caves. One of these contains cave paintings which indicate that the area has been occupied since at least the very early Pre Classic period. ==References==