Biodiversity of Mexico: Mexico is one of the 18 megadiverse countries of the world. With over 200,000 different species, Mexico is home of 10–12% of the world's biodiversity. Mexico ranks first in biodiversity in reptiles with 707 known species, second in mammals with 438 species, fourth in amphibians with 290 species, and fourth in flora, with 26,000 different species. Mexico is also considered the second country in the world in ecosystems and fourth in overall species. Approximately 2,500 species are protected by Mexican legislations.

The Mexican government created the National System of Information about Biodiversity, in order to study and promote the sustainable use of ecosystems. Deforestation is one of the most serious environmental issues in Mexico, with more than one million hectares of forest being lost each year. As of 2002, Mexico had the second fastest rate of deforestation in the world, second only to Brazil. The government has taken another initiative in the late 1990s to expand the people's knowledge, interest and use of the country's esteemed biodiversity, through the Comisión Nacional para el Conocimiento y Uso de la Biodiversidad.

In Mexico, 170,000 square kilometres (65,637 sq mi) are considered "Protected Natural Areas." These include 34 reserve biospheres (unaltered ecosystems), 64 national parks, 4 natural monuments (protected in perpetuity for their aesthetic, scientific or historical value), 26 areas of protected flora and fauna, 4 areas for natural resource protection (conservation of soil, hydrological basins and forests) and 17 sanctuaries (zones rich in diverse species).

The discovery of the Americas brought to the rest of the world many widely used food crops and edible plants. Some of Mexico's native culinary ingredients include: chocolate, avocado, tomato, maize, vanilla, guava, chayote, epazote, camote, jícama, nopal, zucchini, tejocote, huitlacoche, sapote, mamey sapote, many varieties of beans, and an even greater variety of chiles, such as the Habanero and the Xalapeño. Most of these names come from indigenous languages like Nahuatl.

Biodiversity of Mexico

Mexico faces significant environmental challenges affecting almost every section of the country. Vast expanses of southern and southeastern tropical forests have been denuded for cattle-raising and agriculture. For example, tropical forests covered almost half of the state of Tabasco in 1940 but less than 10% by the late 1980s. During the same period, pastureland increased from 20 to 60% of the state's total area. Analysts reported similar conditions in other tropical sections of Mexico. Deforestation has contributed to serious levels of soil erosion nationwide. In 1985 the government classified almost 17% of all land as totally eroded, 31% in an accelerated state of erosion, and 38% demonstrating signs of incipient erosion. Mexico has developed a Biodiversity Action Plan to address issues of endangered species and habitats that merit protection.

Soil destruction is particularly pronounced in the north and northwest, with more than 60% of land considered in a total or accelerated state of erosion. Fragile because of its semiarid and arid character, the soil of the region has become increasingly damaged through excessive cattle-raising and irrigation with waters containing high levels of salinity. The result is a mounting problem of desertification throughout the region.

Mexico's vast coastline faces a different, but no less difficult, series of environmental problems. For example, inadequately regulated petroleum exploitation in the Coatzacoalcos-Minatitlán zone in the Gulf of Mexico has caused serious damage to the waters and fisheries of Río Coatzacoalcos. The deadly explosion that racked a working-class neighborhood in Guadalajara in April 1992 serves as an appropriate symbol of environmental damage in Mexico. More than 1,000 barrels of gasoline seeped from a corroded Mexican Petroleum (Petróleos Mexicanos—Pemex) pipeline into the municipal sewer system, where it combined with gases and industrial residuals to produce a massive explosion that killed 190 persons and injured nearly 1,500 others.

Mexico City confronts authorities with perhaps their most daunting environmental challenge. Geography and extreme population levels have combined to produce one of the world's most polluted urban areas. Mexico City sits in a valley surrounded on three sides by mountains, which serve to trap contaminants produced by the metropolitan area's 15 million residents. One government study in the late 1980s determined that nearly 5 million tons of contaminants were emitted annually in the atmosphere, a tenfold increase over the previous decade. Carbons and hydrocarbons from the region's more than 3 million vehicles account for approximately 80% of these contaminants, with another 15%, primarily of sulfur and nitrogen, coming from industrial plants. The resulting dangerous mix is responsible for a wide range of respiratory illnesses. One study of twelve urban areas worldwide in the mid-1980s concluded that the residents of Mexico City had the highest levels of lead and cadmium in their blood. The volume of pollutants from Mexico City has damaged the surrounding ecosystem as well. For example, wastewater from Mexico City that flows north and is used for irrigation in the state of Hidalgo has been linked to congenital birth defects and high levels of gastrointestinal diseases in that state.

Beginning in the mid-1980s, the government enacted numerous antipollution policies in Mexico City with varied degrees of success. Measures such as vehicle emissions inspections, the introduction of unleaded gasoline, and the installation of catalytic converters on new vehicles helped reduce pollution generated by trucks and buses. In contrast, one of the government's most prominent actions, the No Driving Day program, may have inadvertently contributed to higher pollution levels. Under the program, metropolitan area residents were prohibited from driving their vehicles one day each work week based on the last number of their license plate. However, those with the resources to do so purchased additional automobiles to use on the day their principal vehicle was prohibited from driving, thus adding to the region's vehicle stock. Thermal inversions reached such dangerous levels at various times in the mid-1990s that the government declared pollution emergencies, necessitating sharp temporary cutbacks in vehicle use and industrial production.

The Tropic of Cancer effectively divides the country into temperate and tropical zones. Land north of the twenty-fourth parallel experiences cooler temperatures during the winter months. South of the twenty-fourth parallel, temperatures are fairly constant year round and vary solely as a function of elevation.

Areas south of the twentieth-fourth parallel with elevations up to 1,000 meters (3,281 ft) (the southern parts of both coastal plains as well as the Yucatán Peninsula), have a yearly median temperature between 24 and 28 °C (75.2 and 82.4 °F). Temperatures here remain high throughout the year, with only a 5 °C (9 °F) difference between winter and summer median temperatures. Although low-lying areas north of the twentieth-fourth parallel are hot and humid during the summer, they generally have lower yearly temperature averages (from 20 to 24 °C / 68 to 75.2 °F) because of more moderate conditions during the winter.

Between 1,000 and 2,000 meters (3,281 and 6,562 ft), one encounters yearly average temperatures between 16 and 20 °C (60.8 and 68 °F). Towns and cities at this elevation south of the twenty-fourth parallel have relatively constant, pleasant temperatures throughout the year, whereas more northerly locations experience sizeable seasonal variations. Above 2,000 meters (6,562 ft), temperatures drop as low as an average yearly range between 8 and 12 °C (46.4 and 53.6 °F) in the Cordillera Neovolcánica. At 2,300 meters (7,546 ft), Mexico City has a yearly median temperature of 15 °C (59 °F) with pleasant summers and mild winters. Average daily highs and lows for May, the warmest month, are 26 and 12 °C (78.8 and 53.6 °F), and average daily highs and lows for January, the coldest month, are 19 and 6 °C (66.2 and 42.8 °F).

Rainfall varies widely both by location and season. Arid or semiarid conditions are encountered in the Baja California Peninsula, the northwestern state of Sonora, the northern altiplano, and also significant portions of the southern altiplano. Rainfall in these regions averages between 300 and 600 millimeters (11.8 and 23.6 in) per year, although even less in some areas, particularly in Baja California Norte. Average rainfall totals are between 600 and 1,000 millimeters (23.6 and 39.4 in) in most of the major populated areas of the southern altiplano, including Mexico City and Guadalajara. Low-lying areas along the Gulf of Mexico receive in excess of 1,000 millimeters (39.4 in) of rainfall in an average year, with the wettest region being the southeastern state of Tabasco, which typically receives approximately 2,000 millimeters (78.7 in) of rainfall on an annual basis. Parts of the northern altiplano, highlands and high peaks in the Sierra Madre Occidental and the Sierra Madre Oriental occasionally receive significant snowfalls.

Mexico has pronounced wet and dry seasons. Most of the country experiences a rainy season from June to mid-October and significantly less rain during the remainder of the year. February and July generally are the driest and wettest months, respectively. Mexico City, for example, receives an average of only 5 millimeters (0.2 in) of rain during February but more than 160 millimeters (6.3 in) in July. Coastal areas, especially those along the Gulf of Mexico, experience the largest amounts of rain in September. Tabasco typically records more than 300 millimeters (11.8 in) of rain during that month. A small coastal area of northwestern coastal Mexico around Tijuana has a Mediterranean climate with considerable coastal fog and a rainy season that occurs in winter.

Mexico lies squarely within the hurricane belt, and all regions of both coasts are susceptible to these storms from June through November. Hurricanes on the Pacific coast are often less violent than those affecting Mexico's eastern coastline. Several hurricanes per year strike the Caribbean and Gulf of Mexico coastline, however, and these storms bring high winds, heavy rain, extensive damage, and occasional loss of life. Hurricane Gilbert passed directly over Cancún in September 1988, with winds in excess of 200 kilometers per hour (124 mph), producing major damage to hotels in the resort area. It then struck northeast Mexico, where flooding from the heavy rain killed dozens in the Monterrey area and caused extensive damage to livestock and vegetable crops.

Mexico is crossed from north to south by two mountain ranges known as Sierra Madre Oriental and Sierra Madre Occidental, which are the extension of the Rocky Mountains from northern North America. From east to west at the center, the country is crossed by the Trans-Mexican Volcanic Belt also known as the Sierra Nevada. A fourth mountain range, the Sierra Madre del Sur, runs from Michoacán to Oaxaca.

As such, the majority of the Mexican central and northern territories are located at high altitudes, and the highest elevations are found at the Trans-Mexican Volcanic Belt: Pico de Orizaba (5,700 m, 18,701 ft), Popocatépetl (5,462 m, 17,920 ft) and Iztaccíhuatl (5,286 m, 17,343 ft) and the Nevado de Toluca (4,577 m, 15,016 ft). Three major urban agglomerations are located in the valleys between these four elevations: Toluca, Greater Mexico City and Puebla.

The geography of Mexico entails the physical and human geography of Mexico, a country situated in the Americas.

Location of Mexico: 23° N and 102° W in the southern portion of North America. in a region known as Middle America. Mexico is bounded to the north by the United States (specifically, from west to east, by California, Arizona, New Mexico, and Texas), to the west and south by the Pacific Ocean, to the east by the Gulf of Mexico, and to the southeast by Belize, Guatemala, and the Caribbean Sea. The northernmost constituent of Latin America, it is the most populous Spanish-speaking country in the world.

Almost all of Mexico is on the North American Plate, with small parts of the Baja California Peninsula in the northwest on the Pacific and Cocos Plates. Some geographers include the portion east of the Isthmus of Tehuantepec including the Yucatán Peninsula within North America. This portion includes the five states of Campeche, Chiapas, Tabasco, Quintana Roo, and Yucatán, representing 12.1% of the country's total area. Alternatively, the Trans-Mexican Volcanic Belt may be said to delimit the region physiographically on the north. Geopolitically, Mexico is generally not considered part of Central America.

Mexican territory includes the more remote Isla Guadalupe and the Islas Revillagigedo in the Pacific Ocean. Mexico's total area covers 1,972,550 square kilometers, including approximately 6,000 square kilometers of islands in the Pacific Ocean, Gulf of Mexico, Caribbean Sea, and Gulf of California (see the map.) On its north, Mexico shares a 5000-kilometer border with the United States. The meandering Río Bravo del Norte (known as the Rio Grande in the United States) defines the border from Ciudad Juárez east to the Gulf of Mexico. A series of natural and artificial markers delineate the United States-Mexican border west from Ciudad Juárez to the Pacific Ocean. On its south, Mexico shares an 871 kilometer border with Guatemala and a 251-kilometer border with Belize.

Mexico has a 9,330 kilometer coastline, of which 7,338 kilometers face the Pacific Ocean and the Gulf of California, and the remaining 2,805 kilometers front the Gulf of Mexico and the Caribbean Sea. Mexico's exclusive economic zone (EEZ), which extends 200 nautical miles (370 km) off each coast, covers approximately 2.7 million square kilometers. The landmass of Mexico dramatically narrows as it moves in a southeasterly direction from the United States border and then abruptly curves northward before ending in the 500-kilometer-long Yucatán Peninsula. Indeed, the state capital of Yucatán, Mérida, is farther north than Mexico City or Guadalajara.