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The site called "Arco del Tiempo del Río La Venta" (Arch of Time of La Venta River), is located on an area of geological formations over 87 thousand years old, with predominant karst landforms, because of limestone dissolution. Part of La Venta River is skirted by high cliffs, forming a canyon with limestone walls that reach heights over 500 meters. This canyon has a length of 84 km and many natural caves have been formed in its walls. The whole ensemble is a karst system, which added to tectonic factors, has originated depressions that can be physically observed such as abysses, fissures, dolines and caverns.
It stands out the López Mateos karst system (named as such given its proximity to the homonymous community) which brings together speleological, natural and archaeological wealth in a tropical karst area, unique and emblematic (Bernabei et al. 1999). The caves of La Venta River keep much archaeological evidence of its Prehispanic occupation, as well as important characteristics from the point of view of stratigraphy and culture. The climatic features and the geological context of the area have allowed that artifacts made with organic materials that are rarely conserved in open archaeological sites have been conserved in several caves of the Canyon of La Venta River.
The area has a warm subhumid climate where the shallow hydrology is virtually absent; however, El Ocote Rainforest has an important subterranean river complex, laying an interesting dynamics of underground water circulation in permanent linking with the karst system. The average annual temperature ranges from 21 to 28°C, with an average of 25°C. Rainwater is captured by the extensive rainforest and is driven to the bottom of the dolines, forming a wide hydro-geological collector, capable of storing almost 20 cubic meters of water per second (Giulivo, 1999).
The complex and varied cave system of karst origin that exists in the area is a perfect habitat for many animals that develop their lifecycles inside them or that use them as places for refuge. From the point of view of ecology, the caves are characterized by a very high relative humidity, constant temperature and absolute darkness. Its fauna is composed by organisms with different levels of adaptation to the selective conditions generated by the dark and humid atmosphere of the caves (Sbordoni, 1999). The most evident adaptations of the cavern fauna are morphological and become apparent by the loss of pigmentation in their bodies, the extreme reduction of the eyes to the true anophthalmia and the lengthening of all the appendixes.
The rupestrian art sites represent a cultural expression of the Prehispanic Zoque communities of the region, these are approximately between 5,000 and 10,000 years old; besides, their location is particularly outstanding since they lay on vertical walls. One of the distinguishing features of these expressions, mostly geometric and abstract, is that they represent a code of thinking clearly associated with the firmament and their natural environment.
Human presence in the Canyon of La Venta River has been scientifically recognized after the mid-twentieth century, although its cultural vestiges were well known by the inhabitants that lived and live near from time immemorial. The caves archaeologically studied that have given more cultural relevance to the region are Cueva del Lazo and El Castillo, where ten skeletons of children between six months and seven years old were found. Given the context of these discoveries, it has been archaeologically inferred that they are product of ritual ceremonies associated to the water deities. The botanical remains associated to these skeletons refer to the rites and ceremonies held at the time of the burial of the ten infants. The vegetables found, are partly related to some wild plants and some more are product of the cultivation, giving irrefutable evidence that these communities developed the agriculture.
The climatic features of the caves allowed the conservation of this type of cultural material, commonly perishable, which in another context would not have been preserved naturally. This way, these vestiges allow us to know aspects such as clothing, basketry and wood carving.
In La Venta River Canyon is located the highest natural arch on the planet, 158 meters high, 255 m. long and 35 meters wide. This geomorphologic formation of over 80 million years joins other several scenic beauties of the landscape such as the cascades of La Conchuda and El Aguacero. There are also more than 400 caves with planimetric tours of up to 13 km. Such is the case of the cave of La Venta River, considered as the second largest of the State of Chiapas.
Likewise, more than 38 abysses can be appreciated in the site, with diameters over 100 m. and depths from 100 to 280 m., like Las Luchas abyss, which is the deepest in the area and the third in the country.
The Canyon of La Venta River is a representative example of the geological processes in the Sierra Madre mountain range. The caves are the main morphological feature of this landscape and they constitute an outstanding entrance to the subterranean world. The landscape that is observed at present is a panorama of thick rainforest. On the other hand, the net of subterranean rivers surrounding the area are the result of the effect of the rainwater over the calcareous rocks, within a geo-ecological process of great scale developed along thousands of years.
El Ocote Rainforest is integrated by more than 45,000 hectares of tropical ecosystem and it constitutes some of the most important rainforest fragments in the Mexican Southeast. It is undoubtedly a focal point in the connectivity with the Isthmus of Oaxaca, region where converge the States with the greatest biodiversity in México (Chiapas and Oaxaca).
With records that surpass 1,500 species of plants and animals, a complex cavern system of karst origin stands out for its cavern fauna and diverse environmental services. El Ocote Rainforest Biosphere Reserve constitutes a protected area where the Canyon of La Venta River is located.
The fauna of the caves is formed by unique organisms. Of the 300 species found in the caves of La Venta River Canyon, 180 were new to science and most of them are classified as cavern fauna (blindfish of the Rhamdia genre, semi-troglomorphic crayfish of the Procambarus genus, troglobitic prawn belonging to the Palaemonidae family, etc.).
Since the decade of 1950 there were proposals and efforts to protect El Ocote rainforest (where the Arco del Tiempo del Río La Venta is located) made by naturalists and researchers. In 1972, the Government of the State of Chiapas, established by means of a decree, the protected area called "Área Natural y Típica del Estado de Chiapas, Tipo Ecológico Bosque LLuvioso Alto" (Natural and Typical area of the State of Chiapas, High Precipitation Rainforest Ecological Type), with an extension of 10,000 hectares. Ten years later, in 1982, the Federal Government declared this area as "Zona de Protección Forestal y Fáunica Selva El Ocote" (El Ocote rainforest federal zone of fauna and forest protection) with an extension of 48,140 hectares. Later on, El Ocote rainforest was re-classified and its surface extended to 101,288 hectares, changing its name to natural protected area in the category of biosphere reserve on November 27 of 2000, through a decree published in the Official Newspaper of the Federation.
Currently, El Ocote forest is part of the national system of protected natural areas and it is managed by the Ministry of Environment and Natural Resources (SEMARNAT) through the National Commission of Protected Natural Areas (CONANP). Due to its high diversity and functional ecological integrity, El Ocote rainforest is part of the Región Terrestre Prioritaria No. 132 "Selva Zoque-La Sepultura" (High-priority terrestrial region), appointed by the National Commission for the Study and Use of the Biodiversity.
On October 27 of 2006, México inscribed the Reserve El Ocote in the net of Biosphere Reserves of the Programme on Man and the Biosphere (MAB-UNESCO), with base on the recognition of the importance of the conservation of this natural protected area at national and international level.
Various international organizations recognize the importance of El Ocote rainforest conservation and have contributed to the operation of projects of research, conservation and management; some of these agencies are: The United States Agency for International Development (USAID),The Nature Conservancy (TNC), the European Economic Community (EEC), The World Wildlife Found (WWF), The Klamath National Forest (KNF-USFS), The National Fish and Wildlife Foundation (NFWF), The Fish and Wildlife Service (FWS), The Global Environmental Facility (GEF) and The World Bank (WB). Also, diverse local and national institutions such as the Instituto de Historia Natural, Universidad de Ciencias y Artes de Chiapas, Universidad Autónoma de Chiapas, El Colegio de la Frontera Sur (ECOSUR), Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Universidad Nacional Autónoma de México (UNAM), Universidad Autónoma Metropolitana (UAM), Ecosfera A.C., Ecobiosfera A.C., Pronatura Chiapas A.C. and Aires de Cambio A.C.
The Sumidero Canyon in the State of Chiapas, in contrast to the Canyon of La Venta River, derives from a geological fault and it is 136 million years old; it also has a length of 23 km., walls from 700 to 1200 m. high and variable widths ranging from one to two kilometers. Along it, we can see five waterfalls, two springs, 30 rapids and a gorge three meters wide.
With regard to caves and caverns where archaeological vestiges and rupestrian paintings in vertical cliffs are found, we can mention the prehistoric caves of Yagul and Mitla located in the central valleys of Oaxaca; their caves and shelters marked the transition from a nomadic lifestyle to sedentism and constitute one of the main sites with rupestrian art and development of agriculture from prehistory to the present day. An outstanding similarity is found in the botanical remains registered in both sites, indicating agricultural processes in Yagul and Mitla through remains of squash and maize, and in the case of the caves associated to La Venta River, the botanical remains indicate the use of natural resources and sedentism in the site.
Regarding other natural arches, the Arco del Tiempo del Río La Venta can be compared with the most relevant arches of the world such as: "Landscape" in Arches National Park, Utah, U.S., "Kolob" in Zion National Park, Utah, U.S., "Aloba" in Ennedi Range, Chad (Sahara Desert); "Stevens" in Escalante River, Utah, U.S.; "Shiptons" near Kashgar, in Xinjiang, China; "Jiangzhou" in Guangxi, China and "Outlaw" in Dinosaur National Monument, Colorado, U.S. In the case of México, we have reference of small arches such as "Boca del Diablo" in Baja California Sur, "La Ventana" in Baja California Norte, an unnamed arch in Cozumel, Quintana Roo and "El Arcotete" in San Cristóbal de las Casas, Chiapas.