The biodiversity of Mexico

Biodiversity of Mexico

Covering an area approximately 1,978,000 square kilometers, Mexico is the third largest nation in Latin America after Brazil and Argentina. Its northern border with the United States runs 3,326 kilometers from the Pacific Ocean to the Gulf of Mexico and follows the Rio Bravo del Norte (the Rio Grande in the United States) east of Ciudad Juarez, Chihuahua. The main landmass of the country is in the general shape of a cone that narrows from its broad northern border to the Isthmus of Tehuantepec where the land turns eastward then northeastward to the Yucatan Peninsula. In the southeast, Mexico shares an 871-kilometer border with Guatemala and a 251-kilometer border with Belize. And like the northern border, these "are defined mostly by natural boundaries, such as rivers (the Rio Usumacinta and the Rio Hondo) and partly by artificial boundaries" (Arbingast 32).

Mexico's western Pacific coastline measures 3,974 kilometers and its eastern coastline on the Gulf of Mexico and the Caribbean Sea measures 2,805 kilometers. The narrow peninsula of Baja (Lower) California stretches south from Mexico's northwest frontier and is separated from the main body of Mexico by the Gulf of California. A number of sparsely-inhabited islands also make up part of the Mexican territory. The two largest, Isla Tiburon and Isla Angel de la Guarda, are in the northern half of the Gulf of California; Isla de Cozumel and a number of smaller islands lie off the eastern coast of the Yucatan Peninsula in the Caribbean Sea. According to John Annerino, this region forms "a chain of fifty-five islands, islets and pinnacles that teem with myriad species of flora and fauna, often regarded by many naturalists as Mexico's Galapagos" (75).

It has been suggested that Hernando Cortez, the famous Spanish conqueror of Mexico, described the topography of Mexico by crumbling up a piece of paper, throwing it down and stating "This is a map of Mexico" (Calvert 67). Indeed, Mexico does possess lowland areas, mostly along its coastlines; however, it is true that the topography of the area in between is defined by massive and often forbidding mountain ranges.

The largest mountain range in terns of area is the Sierra Madre Occidental which runs from the northern border south to the state of Jalisco, often attaining a breadth of 300 kilometers or more. The rugged nature of this range which peaks in the state of Durango with several peaks more than 3,000 meters high is attested to by the fact that currently there are only two means of surface transportation, being a highway from Durango to Mazatlan and a railroad from Chihuahua to Los Mochis, traversing it. This incredibly beautiful region of Mexico "is gouged by a labyrinth of torturous canyons, from the 6,136-foot-deep Barranca de Urique in the north to the 7,500-foot-deep Barranca de Piaxtla in the south" (Annerino 60).

All of the major topographical regions of northern Mexico run north and south and can be viewed as extensions of regions within the southwestern United States. The Sierra Madre Occidental is thus an extension of the Sierra Nevada; the Sierra Madre Oriental which defines the eastern edge of the highlands of northern Mexico is an extension of the Rocky Mountains. The Sierra Madre Oriental runs from the border with Texas south to the northern part of the state of Puebla and although narrower than the Sierra Madre Occidental, it reaches higher altitudes, peaking at over 3,700 meters in the state of Nuevo Leon. In this environment, "animal life is rich and is reminiscent of those biomes elsewhere in the world with similar vegetation characteristics" (Moore 85).

Between these two parallel ranges lies a huge plateau which averages about 1,000 meters in altitude at its northern end and slopes gently to twice that height at its southern terminus near San Luis Potosi, known as the Mesa del Norte. The Rio Bravo del Norte whose only major tributary is the Rio Conchos, provides the only surface drainage out of this vast, dry region. As a result, it contains many bolsones or basins that often form shallow lakes from rain runoff. The largest of these is the Bolson de Mapimi which is made up of a much larger area between Torreon and the country's northern border.

To the east of the Sierra Madre Occidental lies the Gulf coastal plain, the southern extension of the Texas coastal plain bordering on the Gulf of Mexico. This plain is quite wide at the Rio Bravo del Norte but gradually narrows as it approaches its southern terminus north of Veracruz. It is traversed by a number of rivers that drain the Sierra Madre Occidental and the coast itself tends to be marshy and fringed by shallow lagoons and sandbars.

On the opposite side of Mexico's wide northern region lie the Pacific coastal lowlands, wedged between the Sierra Madre Occidental and the Gulf of California. Narrower and longer than its counterpart facing the Gulf, the Pacific coastal lowlands stretch from Mexicali south almost to Tepic, Nayarit. Although traversed by many rivers, these lowlands are considerably drier than those on the Gulf coast while their northern portions are the southern terminus of the Sonoran desert.

The peninsula of Baja California is extremely dry and is very mountainous except for two desert plains that extend on the Pacific side. An extension of the Pacific coast range in the United States, Baja California is some 1,200 kilometers long and between 50 and 240 kilometers wide.

Central Mexico extends from approximately 22 degrees north latitude and south to the lowland narrows of the Isthmus of Tehuantepec. As the most mountainous area of Mexico, it contains both the Cordillera Neo-Volcanica and the Sierra Madre del Sur in addition to the Mesa Central which topographically is the southern extension of the Mesa del Norte, the heartland of Mexico. The terrain in this area is made up principally of rolling hills and the extinct cones of many volcanoes interspersed with broad basins and valleys with floors that range in elevation from 1,500 meters to some 2,300 meters in the Valley of Mexico, the location of Mexico City. The five largest basins and valleys extend west-northwestward from the basin of Puebla in the east through the Valley of Mexico and the basins of Toluca, Guanajuato and Jalisco. The Verde Valley, to the north of Jalisco in the state of Aguascalientes, is also part of this geological formation.

The basins to the west of Toluca are interconnected and relatively level and together they form an important sub-region known as El Bajio (flatlands) where "the rich volcanic ash and lacustrine soils from old lakebeds makes this area one of the most productive agricultural zones in the whole of Mexico" (Butland 71). On the southern edge of the Mesa Central lies the Cordillera Neo-Volcanica where Mexico's highest peaks are found. The highest, Pico de Orizaba at an altitude of 5,639 meters, demarcates the eastern edge of the range. The second and third in height, Popocatepetl and Ixtaccihuatl, lie southeast of Mexico City and together with the volcanic peak of La Malinche to the east of the capital, figure prominently in Mexican folklore.

Southeastern Mexico includes all the territory east of the Isthmus of Tehuantepec, being the narrowest point in the country. This lowland isthmus some 250 kilometers wide runs north and south between the Bahia de Campeche and the Golfo de Tehuantepec; from here, a narrow band of lowlands border the Pacific Ocean. On the Gulf side, the isthmus opens up to the broad Tabasco plain which runs from Veracruz on the west to the Yucatan peninsula. The eastern terminus of this plain is quite swampy and dotted with lagoons and is also the location of some of Mexico's richest oil fields.

In a triangular area between these coastal lowlands, one can find the Chiapas Highlands and to their south paralleling the Pacific Ocean, the Sierra de Soconusco. Between these two mountainous regions is a broad depression formed by the Rio Grijalva where two of Mexico's largest reservoirs can be found.

To the northeast, the Chiapas Highlands give way to the lowland tropical rain forest common to the southern Yucatan peninsula and the adjacent region of northern Guatemala known as El Peten. Moving northward up the Yucatan peninsula, "the dense jungle opens up to a tropical savanna and the extreme northern end is quite dry" (Lockwood 145). Virtually the entire peninsula consists of a limestone platform which makes it geologically unique within Mexico but similar to Florida. However, there is no surface drainage and underground rivers can be accessed through numerous sinkholes that dot the entire region.

Within and without all of these topographical and geological regions, vast species of flora and fauna thrive despite the interference of the modern-day world. The Sierra Madre Occidental, the Cordillera Neo-Volcanica and the Sierra Madre del Sur still contain some huge expansions of pine forest and at lower levels forests of great oaks. Tropical forest covers much of the lowest western slopes of the Sierra Madre Occidental and the Cordillera Neo-Volcanica; such luxuriant flora can also be found in the Oaxaca. These forests "loose their leaves during the dry winter but are lush and verdant in the summer rainy season" (Lewis 82).

Some of the varieties of flora in these regions include the pink trumpet, cardinal sage and the spider lily. Along the dry Pacific coastal plain, from the southern end of the Sonora desert to the state of Guerrero, the predominant vegetation is thorny bushes and small trees, including morning glory, acacias and savanna. Some of this flora occurs naturally, while others occur on over-grazed grasslands or abandoned slash-and-burn farmlands. Patches of semi-deciduous tropical forest reach almost to the sea near the Guerrero-Michoacan border. The coastal lagoons that dot the Pacific coast are home to dense mangrove forests that have thick, leathery leaves and small seasonal flowers.

As to the fauna, many animals can be found living among the lowland plains and along the edges of the vast mountainous areas both north and south. Creatures such as raccoons, armadillos, skunks, rabbits and many varieties of both poisonous and non-poisonous snakes are very common. Of course, many species of reptiles are here too, such as the gecko, collared lizards, gila monsters and horned toads. Black and green iguanas are also common along the entire Mexican coast. These two reptiles, prized for their tender meat, have been over-hunted, especially in Guerrero and Oaxaca, almost to point of extinction; however, "through the efforts of conservationists and the Mexican government, most of the iguana species are now protected.

The Pacific coast is among the world's chief breeding ground for the sea turtle, another endangered species. Dolphins can often be spotted off the coast as can gray, humpback and blue whales, especially from November to March; sting rays and the larger Pacific manta ray are found here as well. Tide pools often harbor sea anemones, urchins, octopi, starfish, sea slugs and a vast assortment of crabs. In addition, the "most obvious plants in these rocky shores are red, green and brown algae... A major food source for many larger sea animals" (Moore 100). Also, in the coastal lagoons, especially in the south, crocodiles can still be found, yet their numbers have dwindled greatly, due to being almost hunted to extinction.

The lagoons and wetlands of the Pacific coast also contain hundreds of species of native and migratory birds that come from as far as Alaska each winter. There are also parrots and parakeets, loons, grebes, frigatebirds, herons, hawks, falcons, sandpipers, swifts and ibises, just to name a few. In Oaxaca, it is not uncommon for ospreys to be seen soaring high above the ocean cliffs.

The climate of Mexico varies greatly, due to its considerable north to south extension and the variations in its altitudes. The Tropic of Cancer which demarcates the northern edges of the tropics bisects the country just north of Mazatlan. However, it is inaccurate to view northern Mexico as temperate and southern Mexico as tropical, for in fact the country is divided into three climatic vertical zones, being the tierra caliente (hot land), tierra templada (temperate land) and tierra fria (cold land). For example, in the tierra templada, one can find "the warm, temperate rain forests, where the life forms of the major trees are the broad-leaved evergreen which reach as far down as Brazil" (Moore 48).

The tierra caliente runs from sea level to approximately 1,000 meters in altitude and includes all of the coastal plains, the Yucatan peninsula, Baja California, the Isthmus of Tehuantepec and the north-central portion of the Mesa del Norte. The mean annual temperature in this zone is twenty-four to twenty-seven degrees Celsius but it is not uncommon in some low-lying areas for temperatures to exceed thirty-eight degrees Celsius.

Except in the Mesa del Norte, the variation in temperatures between summer and winter is relatively small in the tierra caliente. Rainfall varies tremendously among the different areas -- the Tabasco plain, the nation's wettest region, receives in excess of 200 centimeters of rain annually, while Baja California, the northern Pacific coastal lowlands and the north-central Mesa del Norte are all extremely dry, receiving no more than 40 centimeters of rain in a year.

The tierra templada is basically the highland valleys that range from about 1,000 to 2,000 meters in altitude. This zone has the most favorable climate and the mean annual temperatures range from eighteen to twenty-four degrees Celsius. Nights are often much cooler but there is only a small temperature variation between the summer and winter months. In southern Mexico, May is often the warmest, for the heavy afternoon rains during the months of June to September moderates the summer temperatures.

The tierra fria which begins above 2,000 meters averages some five degrees Celsius cooler than the tierra templada. Summer temperatures are rarely hot in this zone and frost during winter nights is not uncommon. But in the northern mountainous regions, the temperatures vary greatly, due to the extreme altitudes.

It is estimated that only about one-eighth of Mexico's territories receives adequate rainfall year round. About one-half of the territory is deficient during the dry season and south of Tampico, the prevailing winds are northeast trade winds that emanate from the Gulf of Mexico. Along the Gulf coast during the winters, strong, cold, northerly winds called nortes are common and can often be quite destructive. The Caribbean and Gulf coasts are also subject to hurricanes during the summer and autumn months.

As to the ethnic categories of Mexico, anthropologists have traditionally divided it into two categories, being the Indian and the Mestizo. North of the Isthmus of Tehuantepec the term mestizo was used for many years, while south of the isthmus, especially in the state of Chiapas, those of mixed Indian-Hispanic heritage were called Ladinos. However, in the Yucatan peninsula, the concept of metizo had a completely different meaning, for it referred to the indigenous Maya; thus, as anthropologist Julian Pitt-Rivers states "it was virtually impossible to make any statement about Indians or Mestizos that was applicable nationwide, for these concepts referred to highly qualitative and heterogeneous ethnic categories" (Ehrlich 214). In the 1980's, the terms indio (Indian) and mestizo continued to be used colloquially despite their varying connotations. In common language, indio was usually a term of denigration and in official language, Mexico prided itself on being the heir of two civilizations and a culture that was a combination of both. This was, and still is, based on the achievements of the Olmecs, Zapotecs, Toltecs and the Maya that culminated in the rise and fall of the Aztecs.