How important is the fishing industry in Mexico?

 Excerpts from Geo-Mexico  Comments Off on How important is the fishing industry in Mexico?
May 262012
 

The fishing industry now accounts for only 0.24% of gross national product. The relatively shallow waters off the Pacific coast and abundance of plankton in waters cooled by the Californian current make for particularly good fishing in the north-west. Together, Sinaloa (23%) and Sonora (22%) account for about 45% of the national total. Fishing is also economically important in Veracruz (8%), Baja California Sur (6%), Campeche and Baja California (5% each) and Yucatán.

Mexico's fishing fleet

Mexico's fishing fleet

Almost three quarters (72%) of the total annual catch of 1.5 million metric tons is landed at Pacific coast ports such as Guaymas, Mazatlán and Manzanillo. Gulf coast ports like Tampico, Veracruz and Campeche, together with Caribbean coast ports such as Puerto Morelos and Progreso, account for a further 25% of the catch. The remaining 3% comes from inland lakes, rivers and fish farms.

In terms of value, the most important species are shrimp, tuna and sardines. Fresh-water fish farms are becoming more common, with many of them specializing in the production of high value species such as trout and indigenous white fish. Mexicans consume only 13 kg (29 lbs) of fish per person per year on average, considerably less than the equivalent figures for the USA (21 kg), Canada (24 kg) or Spain (44 kg).

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Mexico City in colonial times: 1530–1820

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May 212012
 

The internal geography of cities is closely related to transportation technology. Pre-Columbian cities in Mexico were walking cities; the wheel had not been developed and animals were not used for transport. Human power moved people and goods, but not very quickly or efficiently. As a result, cities were relatively compact and congested; densities were high. Despite these transport restrictions, at least one urban center in pre-Columbian Mexico had a population estimated to exceed 200,000.

The Aztec capital Tenochtitlan was built on an island in the middle of a lake, and was a thriving city when Hernán Cortés arrived. After the conquest, the Spaniards built their colonial city directly on top of Tenochititlan’s main buildings and large central plaza or Zócalo. Spanish colonial urban centers were explicitly patterned after cities in Spain, with a grand central square or plaza at the center (large enough for displays of horsemanship). The streets were laid out following a north-south, east-west grid. In larger cities, smaller plazas might be planned every four blocks or so.

Panoramic view of Mexico City during colonial times

Panoramic view of Mexico City during colonial times. (Talavera tiles based on unattributed oil painting in the Franz Mayer Museum, Mexico City).

Colonial Mexico City conformed closely to the Latin American city model. Important government, commercial, and religious buildings, such as the Cathedral, faced onto the square. Status was largely correlated with distance from the main plaza, the hub of all activity. Wealthy and important colonial officials had large homes in a zone surrounding the main square. This zone tended to be square or rectangular given the grid pattern of streets. Less important, middle income families lived in smaller houses farther from the main plaza; lower status groups lived even farther from the main square. The lowest status mestizos and Indians lived around the outside of the city. The city was very compact and congested. The wealthiest residents in the center lived relatively close to the poorest families on the periphery. With the very high densities, there was considerable noise and congestion, as well as sanitation problems and other health issues.

As Mexico City and other major Latin American cities grew throughout the 300-year colonial period, they tended to maintain a roughly concentric pattern; however, the growth of important government and business activities as well as wealthy residential neighborhoods usually favored one side of the city.

As these high status activities expanded they slowly took over middle status areas, which in turn expanded into poorer neighborhoods. The poorest groups were pushed to the periphery or to undesirable steep hillsides or low areas prone to flooding. The rate of spatial expansion never managed to keep pace with the growth of population and economic activity. Densities and congestion increased.

From the very beginning in Mexico City, a high status sector extended west of the Zócalo. The Aztecs considered Chapultepec Hill, six kilometers (3.6 mi) west of Tenochtitlan, a royal retreat. They built a castle there, connected to their island capital by along causeway. Spanish King Charles V declared the zone a nature reserve in 1537. Early colonial Viceroys built palacial residences there. In 1592, Viceroy Luis de Velasco constructed an impressive park, the 90-hectare (216-acre) Alameda Central about a kilometer west of the Zócalo. The area between the Alameda and the Zócalo became the city’s highest status area. The development decisions made during the 16th century solidified the west as the preferred direction and set the pattern of growth for the next 400 years. Similar high status sectors evolved in virtually all Latin American colonial cities.

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Mexico’s highest volcanoes

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Apr 302012
 

In a previous post, we saw how most of Mexico’s volcanoes are located in a broad band that crosses central Mexico known as the Volcanic Axis (Eje neovolcánico). In this post, we provide brief descriptions of some of the major volcanoes in Mexico.

Starting in the west, the first active volcanoes are Everman and Barcenas in the Revillagigedo Islands. Two of the westernmost volcanoes on the mainland are near Colima. At 4260 m (13,976 ft), the inactive Nevado of Colima, Mexico’s sixth-highest peak, is as tall as the highest mountains in the contiguous USA. Its younger brother, Colima Volcano (or Volcán de Fuego) is lower (3820 m) but highly active and considered potentially very dangerous. It has erupted in cycles for several hundred years, and is capped by a dacitic plug characteristic of a silica-rich Pelean volcano. Such volcanoes have the potential to erupt suddenly, not emitting vast quantities of molten lava, but shooting out less spectacular, but far more devastating, clouds of red‑hot asphyxiating gasses.

Tequila Volcano, overlooking the town where the beverage is distilled, is also in Jalisco. In neighboring Michoacán state, the most noteworthy volcanoes are Jorullo (which last erupted in 1759) and Paricutín, which began life in a farmer’s field in 1943 and ceased activity in 1952, but only after its lava had overwhelmed several small villages.

Closer to Mexico City, the Nevado of Toluca (4680 m) has a drive-in crater and is a favored destination for Mexico City families in winter to take their children to play in the snow. It is Mexico’s fourth highest peak (see table below).

VolcanoStatesHeight (meters)Height (feet)
Pico de OrizabaVeracruz; Puebla5 61018 406
PopocatapetlMéxico; Morelos; Puebla5 50018 045
IztaccihuatlMéxico; Puebla5 22017 126
Nevado of Toluca México 4 68015 354
MalincheTlaxcala; Puebla4 42014 501
Nevado of Colima Jalisco4 26013 976
Cofre de PeroteVeracruz 4 20013 780
TacanáChiapas 4 08013 386
TelapónMéxico 4 06013 320
El AjuscoFederal District3 93012 894
Colima VolcanoJalisco; Colima3 82012 533

Continuing eastwards, we reach several other volcanoes that are among Mexico’s highest volcanic peaks (and are also included in the table).

The most famous volcano in the Volcanic Axis is the still active Popocatepetl (“Popo”), which rises to 5500 meters (18,045 feet). Alongside Popocatepetl is the dormant volcanic peak of Iztaccihuatl (5220 m or 17,126 ft). On a smog-free day, both are clearly visible from Mexico City. The southern suburbs of Mexico City are overshadowed by a smaller active volcano, Ajusco, which reaches 3930 m (12,894 ft).

The Nevado de Toluca volcano

The Pico de Orizaba, a dormant volcano on the border between states of Veracruz and Puebla, is Mexico’s highest mountain. At 5610 m (18,406 ft) it is the third highest peak in North America. By way of contrast, not very far away, in the outskirts of the city of Puebla, is the world’s smallest volcano!

Only a few volcanoes appear to be located outside the Volcanic Axis and therefore in an anomalous location to the general pattern. They include two volcanoes in Chiapas which lie south of the Volcanic Axis: El Chichón (which erupted in 1982) and Tacaná (4080 m).

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Mexico’s Volcanic Axis

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Apr 192012
 

Mexico’s active seismic zones have created numerous volcanoes, many of which are still active. Virtually all the country’s active and recently dormant volcanoes are located in a broad belt of high relief which crosses Mexico from west to east: the Volcanic Axis (see map).

volcanic-axisAltitudes in this region vary from a few hundred to several thousand meters. The principal peaks are shown on the map. They include many of Mexico’s most famous mountains, such as Popocatepetl and Iztaccihuatl, near Mexico City; Pico de Orizaba, Mexico’s highest peak; Paricutín, the only completely new volcano in the Americas in recent times; and Colima, considered the most active at present. Many of the volcanoes are surprisingly young. For instance, a study using Carbon‑14 dating on the palaeosols (ancient soils) under 12 volcanoes in the Toluca area yielded ages ranging from 38,600 to 8400 years before present.

It is unclear precisely why this broad belt of Mexico should be so active. Elsewhere in the world all major tectonically active areas have been linked in terms of their location to the margins or meeting‑zones of tectonic plates. Some Mexican geologists believe that Mexico’s Volcanic Axis is a rare example of activity associated with a gently dipping plate margin, one where the edge of the Cocos plate is subsumed, but at only moderate gradient, beneath the North American plate.

Almost all the volcanic activity in this zone has taken place in the last 25 million years, from the upper Oligocene period, through the Miocene and Pliocene and up to Recent. Two distinct periods of activity are recognized by some geologists. The first, in the late Oligocene and early Miocene, produced volcanic rocks often found today tightly folded by later earth movements. The second, responsible for all the major composite cones as well as dozens of ash and cinder cones, started in the Pliocene and continues today.

Erosion has had relatively little time to work on these “new” volcanic peaks, some of which are still developing. As a result, this region includes Mexico’s highest mountains, reaching over 5500 m or 18,000 ft.

Thick, lava-rich volcanic soils make this one of the most fertile areas in North America. Though the relief is very rugged, this area has supported relatively high population densities for hundreds of years, including the current large metropolitan areas of Mexico City, Guadalajara and Puebla. Legacies of previous volcanic activity are found in craters, mud‑volcanoes, geothermal activity, and the numerous hot springs (and spa towns) scattered throughout the Volcanic Axis.

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How has the movement of tectonic plates affected Mexico?

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Apr 122012
 

In a previous post, we identified the tectonic plates that affect Mexico. In this piece, we look at some of the major impacts of Mexico lying on or close to so many different plates.

To the east of Mexico, in the last 100 million years, outward expansion from the Mid-Atlantic Ridge (a divergent boundary) first pushed South America ever further apart from Africa, and then (slightly more recently) forced the North American plate (and Mexico) away from Eurasia. The Atlantic Ocean continues to widen, expanding the separation between the New World and the Old World, by about 2.5 cm (1 in) each year.

Mexico's position in relation to tectonic plates

Mexico's position in relation to tectonic plates.Map: Geo-Mexico.com; all rights reserved

Meanwhile, to the west of Mexico, an analogous situation is occurring in the Pacific Ocean, where the Cocos plate is being forced eastwards away from the massive Pacific plate, again as a result of mid-ocean activity. The Cocos plate is effectively caught in a gigantic vice, its western edge being forced ever further eastwards while its leading eastern edge smacks into the North American plate.

The junction between the Cocos and North American plates is a classic example of a convergent plate boundary. The collision zone is marked by a deep ocean trench, variously known as the Middle America trench or the Acapulco trench. Off the coast of Chiapas, this trench is a staggering 6662 m (21,857 ft) deep. The trench is formed where the Cocos plate is forced to dive beneath the North American plate.

As the Cocos plate is subducted, its leading edge fractures, breaks and is partly re-melted into the surrounding mantle. Any cracks in the overlying North American plate are exploited by the molten magma, which is under immense pressure, and as the magma is forced to the surface, volcanoes form. The movement of the plates also gives rise to earthquakes. The depth of these earthquakes will vary with distance from the deep ocean trench. Those close to the trench will be relatively shallow, whereas those occurring further away from the trench (where the subducting plate is deeper) will have deeper points of origin.

As the plates move together, sediments, washed by erosion from the continent, collect in the continental shallows before being crushed upwards into fold mountains as the plates continue to come together. A line of fold mountains stretches almost continuously along the west coast of the Americas from the Rocky Mountains in Canada past the Western and Southern Sierra Madres in Mexico to the Andes in South America. Almost all Mexico’s major mountain ranges—including the Western Sierra Madre, the Eastern Sierra Madre and the Southern Sierra Madre—formed as a result of these processes during the Mesozoic Era, from 245 to 65 million years ago.

However, no sooner had they formed than another momentous event shook Mexico. About 65 million years ago, a giant iridium-rich asteroid slammed into the Gulf of Mexico, close to the Yucatán Peninsula, causing the Chicxulub Crater, and probably hastening the demise of the dinosaurs. An estimated 200,000 cubic km of crust was pulverized; most of it was thrown into the air. The resulting dust cloud is thought to have contributed to the extinction of up to 50% of all the species then on Earth. Not only did this event have an enormous impact on all life forms on Earth, it also left a legacy in the Yucatán. The impact crater is about 200 km (125 mi) across. Its outer edge is marked by a ring of sinkholes (locally known as cenotes) and springs where the fractured crust provided easy access to ground water. These locations include the ria (drowned river valley) of Celestún (now a UNESCO Biosphere Reserve), where fresh water springs mingle with salt water to create an especially rich habitat for birdlife.

In the 65 million years since the asteroid impact (the Cenozoic period), the remainder of Mexico has been formed, including many of the plateaus and plains, and the noteworthy Volcanic Axis, which owes its origin to still-on-going tectonic activity at the junction of the North American and Cocos plates.

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Which tectonic plates affect Mexico?

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Apr 022012
 

The theory of plate tectonics suggests that the earth’s crust or lithosphere is from 5 to 65 km (3 to 40 mi) thick and divided into about a dozen large tectonic plates, tabular blocks that drift across the Earth in different directions and at various speeds (up to a few centimeters or inches per year), probably as a result of thermal convection currents in the Earth’s molten mantle. Most plates consist of a combination of both ocean floor and continent, though some are entirely ocean floor.

Each tectonic plate is moving relative to other plates. The movements are not independent because the plates smash into and scrape against one another. Areas in the center of tectonic plates, far from the boundaries, have relatively little seismic activity, but the boundaries between plates are seismically very active, creating earthquakes and volcanoes. The level of seismic activity depends on the relative speed and direction of the plates at the boundary.

There are three distinct kinds of boundaries between plates. At divergent boundaries, along mid-ocean ridges, plates are being steadily pushed apart, with new crust being added by volcanic activity to the rear of each plate as it moves. At convergent boundaries, plates collide and parts of the plates either buckle or fracture or are subducted back down into the molten mantle. The third kind of boundary is where plates are neither created nor destroyed but are moving side by side. The resulting friction as they rub against each other can produce large earthquakes.

Almost all of Mexico sits atop the south-west corner of the massive North American plate (see map). Immediately to the south is the much smaller Caribbean plate. The North American plate extends westwards from the Mid-Atlantic Ridge, which runs through Iceland and down the middle of the Atlantic Ocean, to the western edge of North America. In a north-south direction, it extends from close to the North Pole as far south as the Caribbean.

Mexico's position in relation to tectonic plates

Mexico's position in relation to tectonic plates.Map: Geo-Mexico.com; all rights reserved

While most of Mexico rests on the North American plate, it is also influenced by several other plates.

The Baja California Peninsula is on the gigantic Pacific plate, which is moving northwest and under the North American plate. The intersection of these plates under the Gulf of California causes parallel faults which are part of the famous San Andreas Fault system. Thus, the Gulf of California is an area of heavy seismic activity.

The small Rivera plate, between Puerto Vallarta and the southern tip of Baja California, is moving in a southeasterly direction and rubbing against the Pacific plate; it, too, is moving under the North American plate.

The Cocos plate and tiny Orozco plate are ocean crust plates located off the south coast of Mexico. The collision of the Cocos plate and the North American plate has had several far-reaching consequences, including both the disastrous 1985 earthquakes that caused such severe loss of life and damage in Mexico City and the much more recent 2012 earthquake that, fortunately, was far less destructive.

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Mexico’s political system: the basics

 Excerpts from Geo-Mexico  2 Responses »
Mar 312012
 

In a few months time, Mexicans go to the polls to elect a new President. Just how does the Mexican political system work? As a build-up to the important federal elections coming shortly, this post looks at the background to Mexico’s political system and provides a quick summary of the federal level of government. A future post will look at the state and municipal levels.

The current political system in Mexico derives from the Constitution of 1917 which emerged from the Mexican Revolution. The Constitution is a sweeping document that captures the ideals of the Revolution, but also reflects three centuries of Spanish colonial rule. The Constitution is “revolutionary” in that it aggressively protects the rights of workers, peasants and their organizations. It guarantees the right to organize, an eight-hour work day, the rights of female and child workers, and the payment of a minimum wage sufficient to satisfy the necessities of life. The colonial influences are evidenced by highly codified civil law, acceptance of heavy state involvement in civic affairs and business, and the relative strength of the executive over other branches of government. Another important influence is Mexico’s 19th century history which included foreign military occupations, loss of half the national territory and several virtual dictatorships.

The government of the United Mexican States has three branches: executive, legislative, and judicial.

The executive branch is by far the most important and most powerful. The President serves a six-year term, may never be re-elected, and appoints the 18 cabinet secretaries who run their respective secretariats or ministries. The full cabinet meets only rarely. Legislation must be signed by the President to become law. Though the legislature may override a veto, the Constitution dictates that laws can only be enacted after being signed by the President. The President has the power to issue basic rules (reglamentos) independent of the legislature. In fact, most Presidents unilaterally issue more Mexican laws than are passed by the legislature.

The legislature consists of a Senate and a Chamber of Deputies. The 128 senators serve the same six-year term as the President and cannot be re-elected. Each state and the Federal District has two senators from the party getting the most votes in that state and one from the party getting the second most votes.

These 96 senators do not represent equal numbers of constituents. Smaller states have greater representation. For example, in the State of Mexico there are about 4.7 million people per senator whereas in Baja California Sur there are only about 170,000 people per senator. The remaining 32 senators are elected by proportional representation based on the percentage of the national vote obtained by each party. These senators do not have geographical constituents.

There are 500 deputies in the Chamber. Geographic districts directly elect 300 deputies; the remaining 200 are elected by proportional representation. A party must win at least 2% of the national vote to get a deputy in the Chamber. They serve three-year terms and cannot be re-elected.

The ban against re-election means that every three years there is an entirely new Chamber of Deputies. Every six years Mexico has a new President and all new legislators. The ban on re-election diminishes the continuity as well as the overall experience and expertise of Mexican government at all levels.

The judiciary is divided into federal courts and state courts. The federal courts have jurisdiction over constitutional issues, most civil cases (contracts, labor issues, banking and commerce) as well as major felonies (bank robberies, kidnapping), except murder. State courts handle murders, divorces and minor felonies. The Supreme Court consists of 26 judges, selected by the President and confirmed by the Senate. Legally, they serve for life but actually submit their resignation to the new President every six years. Below the Supreme Court are four chambers of judges dealing with criminal, civil, labor and administrative issues. There are 16 federal circuit courts and 68 district courts.

The eruption of El Chichón volcano in 1982

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Mar 282012
 

Not all volcanoes give any warning of impending activity. Exactly thirty years ago, just before midnight 28/29 March 1982, the El Chichón volcano in Chiapas erupted completely without warning and with unexpected fury.  Two further eruptions followed in early April. The lack of warning caused heavy loss of life among local villagers who had been unable to evacuate their villages. About 2,000 people lost their lives as a result of the eruption.

Palenque covered in ash following the eruption of El Chichón

Palenque covered in ash following the eruption of El Chichón. Photo: Tony Burton; all rights reserved.

Ash from El Chichón fell over a wide area of southern Mexico. The nearby Mayan archaeological site of Palenque (set on the edge of what is normally a luxuriant, tropical-green jungle) was covered in ash (see photo above).

Concerned about the potential for the ash to combine with rainfall and form an acidic solution that might erase delicate and intricately carved stones, workers at the site engaged in a major clean up, even before all the ash had stopped falling. The second photo (below) shows a worker on top of one of Palenque’s distinctive roof combs sweeping the recently-fallen ash off the structure.

Sweeping ash off Palenque following the eruption of El Chichón

Sweeping ash off Palenque following the eruption of El Chichón. Photo: Tony Burton; all rights reserved.

Vulcanologists later worked out that the last previous eruption of El Chichón had been 1200 years earlier. The eruption “left behind a brooding, sulfuric, acidic lake that formed when the dome collapsed into a crater and filled with water.”

Aztec glyph for a “hill that smokes”

El Chichón forced more than 7 million tons of sulfur dioxide and 20 million tons of particulate material into the stratosphere. The resultant cloud of volcanic gases circled the Earth in three weeks and was still dissipating three years later. It was expected that the additional particulates in the atmosphere would reduce the solar radiation reaching the earth and cause the following summer to be cooler than usual. However, in an unlikely coincidence, an El Niño event began that same year, negating any significant cooling effect from the volcano’s particulates.

The El Chichón eruption was one of the largest volcanic eruptions of the 20th century, exceeded only by the 1991 Mt. Pinatubo eruption in the Philippines in terms of the amount of volcanic gases and particulates entering the stratosphere. Ash fell over a wide area, from Campeche to San Cristóbal de las Casas in Chiapas.

By the time the eruption was over, the volcano, whose summit had been 1260 m (4134 ft) prior to the eruption, had lost 200 m in height. The Chiapanecan Volcanic Arc, which includes El Chichón, falls outside Mexico’s Volcanic Axis (the location of almost all Mexico’s volcanoes) and is thought to be related to the subduction of the edge of the Cocos Plate underneath the North American plate.

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Do paved roads lead to development?

 Excerpts from Geo-Mexico, Updates to Geo-Mexico  Comments Off on Do paved roads lead to development?
Jan 042012
 

In chapter 24 of Geo-Mexico, we described a typology of rural settlement locations and wrote that “rural localities near roads” (defined as those settlements within 3 km (2 mi) of a paved road) are an important category since they house 54% of all Mexico’s rural population. In fact, such settlements account for almost 90% of rural population in Quintana Roo and over 70% of the rural population in the states of Zacatecas, Yucatán, Campeche, San Luis Potosí, Nuevo León and Coahuila.

We explained that while “One of us believes that the location of paved roads is having an impact on rural settlement patterns, the other believes that rural settlement patterns are having an impact on the location of paved roads! Both viewpoints may be correct with their relative importance depending on the region in question.”

Shortly after the publication of Geo-Mexico, a loyal reader (“Jerezano“) wrote to us, agreeing with us, and sharing his personal insights into “rural localities near roads” based on his 23+ years living in the beautiful, small town of Jerez, in the state of Zacatecas. He writes,

“You are both correct, of course.”

“The rural settlement was in most cases located where it was long before the roads were paved. A municipality (municipio), when it decides to pave a road, considers many things:

  • a) Where does the money come from? Local residents, associations of residents in foreign countries who send money back for improvements? and municipal and federal matching funds?
  • b) Existing population figures which of course influence the traffic on the roads.
  • c) Economic contribution of that rural community to the welfare of the state and municipality.”

“So, a rural community with a fairly large population, a robust economy, and an active out-of-town group of supporters, will get a paved access road long before a different community which lacks those attributes. That is easily observable in almost any location.”

“But, once that access road has been paved, the influence is also usually observable by the improved economy of that community. Easy access of products to markets, easy access of potential new residents to the city, etc. will stimulate increases in costs of real estate, living, etc.”

“Here in Zacatecas, for example, the paving of the road to Susticacán from the Jerez-Guadalajara highway stimulated a building boom which is still in progress. The construction of the new 4- lane divided highway from Zacatecas City to Concepción de Oro, and now underway from Concepción de Oro to the Coahuila border, has created an extremely active trailer stop at the Villa de Cos intersection. Before the new highway was started, that intersection was a place with potential and people who had constructed facilities such as restaurants, hotels and a gasoline station were waiting with baited breath.”

Mexican trucks“They are now reaping the benefits of the movement of many, many tractor-trailers from the Ramos Arizpe to San Luis Potosí highway and on to Mexico over to the new Ramos Arizpe to Zacatecas to Mexico highway. At the Villa de Cos intersection where, in the past, you would see pickups, quarter ton, 3/4 ton and a maximum of 4 to 10 ton trucks, you can now see as many as 10 to 20 semi-trailers and doble-remolques (double drop trailers) parked in front of the main restaurant and hotel. All this because the road has been steadily improved over the years from a narrow, two lane Federal highway, with a bad surface most of the distance, to the modern 4 lane divided highway easily transited by rigs which (God forbid) are really too big to be on the highways.”

We sincerely thank Jerezano for taking the time to share these valuable personal insights into rural roads in his “neck of the woods” in Zacatecas, and hope that the New Year brings him and all our readers Health, Happiness and Prosperity.

The changing climate of Mexico’s urban areas

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Dec 312011
 

As large urban areas grow in size, they change their local climate in various ways. The best known effect is that called the urban heat island: the air above cities is significantly warmer than the surrounding air in suburban and rural areas. The transfer of heat energy from people, homes, vehicles and factories warms the air immediately above the city. The irregular built-up surfaces of a city absorb more energy than nearby vegetated areas, also helping to raise the city’s temperature. The difference in temperature is most noticeable just before sunrise.

Wind speeds in cities tend to be lower than in their rural outskirts. Precipitation tends to be slightly higher, as a result of the additional heat energy, which causes mid-afternoon instability, and because city air has higher concentrations of particulates (dust, smog, contaminants) from vehicles and factories.

Urban heat island (°C) in Puebla, Mexico

Urban heat island (°C) in Puebla, Mexico, 2200 h, 11 November 1970 (Source: G.M. Gäb, 1976)

Mexican cities are no exception. The urban heat island differential has risen by an average of 0.44ºC per decade for large cities (population over one million), and by 0.37ºC per decade for mid-sized cities (population between 150,000 and 1,000,000). These rates are clearly greater than the background effect of global warming, variously estimated at between 0.07 and 0.20ºC a decade.

There is no doubt that accelerated urbanization has warmed and is continuing to warm urban air, affecting the comfort levels of millions of people. The cities where urban temperatures have risen most rapidly are Torreón, which warmed at a rate of 1.2ºC per decade from 1952–1998, and Guadalajara, where temperatures rose by 0.74ºC a decade from 1920–1997. [Jauregui, E. 2005. Impact of Increasing Urbanization on the Thermal Climate of Large Mexican Cities]

The case of Mexico City shows an additional complication. At the end of the 19th century, comparing minimum temperatures, Mexico City (population then 400,000) was about 1.5ºC warmer than surrounding areas. This difference had risen dramatically to about 9ºC (16ºF) by the 1980s. Urbanization has certainly played a part, and its effects have perhaps been exacerbated by the city’s unfortunate position in a basin, which traps air, heat and contamination. However, climate modeling suggests that the loss of lakes in the Valley of Mexico, including the draining of most of Lake Texcoco, has played at least as large a part in Mexico City’s increased temperatures as the expansion of its urban area. [Jazcilevich, A. et al. 2000. Simulated Urban Climate Response to Historical Land Use Modification in the Basin of Mexico. Climatic Change 44]

In addition, the incidence of intense rain showers (those where more than 20 mm (0.8 in) falls per hour) in Mexico City has also risen steadily, from four a decade in the 1940s to twenty a decade in 1980s. There is, however, no convincing evidence that wet season rainfall totals have increased, despite the combination of increased temperatures and instability, and the higher number of particulates in the air from dust, vehicle exhausts and factories. Away from the edge of the city, precipitation appears to have declined. [Jauregui, E. 2004. Impact of land-use changes on the climate of the Mexico City Region. Mexico City: Boletín del Instituto de Geografía.]

In summary, the expansion of Mexico City appears to have led to warmer, drier conditions in the Valley of Mexico.

Urban areas also have distinctive effects on hydrology. The roads and buildings of cities form impermeable surfaces which reduce infiltration almost to zero and greatly increase surface runoff. The lag time between a rainstorm and peak discharge in stream channels is much less in urban areas than in their rural surroundings. This makes the likelihood of flooding much greater in urban areas. In most cities, surface runoff is channeled rapidly into gutters and drains (a form of high speed throughflow) in an effort to reduce flood risk.

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Mexico’s freshwater aquifers: undervalued and overexploited

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Nov 052011
 

Mexico’s groundwater aquifers are a very important resource. About 64% of public water supplies come from wells sunk into aquifers. Mexico City, Monterrey and several other metropolitan areas rely heavily on aquifers. Aquifers also provide about one-third of all the water for agriculture and livestock.

The largest aquifer resource in terms of renewable water availability is in the Yucatán Peninsula, with about a third of the national total. A large portion of the rainfall in the Yucatán seeps into its aquifers; there are virtually no rivers to carry rainwater to the ocean. The states of Chiapas and Tabasco, where rainfall is the heaviest, account for about a quarter of Mexico’s aquifer resource. The next largest sources are the Balsas and Lerma–Santiago basins but each holds less than a tenth of the national total.

Map of overexploited aquifers and areas of salinization

Overexploited aquifers and areas of salinization (Fig 6-7 of Geo-Mexico; all rights reserved)

According to the National Water Commission, 104 of the country’s 653 identified aquifers are overexploited in that more water is withdrawn each year than is naturally replaced. The velocity of water movements underground can be astonishingly slow; it may take rainwater water tens or even hundreds of years to reach the aquifer it is replenishing. (For a curious case of replenishment rates, see The Enchanted Lake).

The number of overused aquifers has increased rapidly in recent decades from 32 in 1972, to 80 in 1985, and 104 in 2004. When coastal aquifers are over-exploited, seawater seeps in to replenish the aquifer, and eventually the aquifer can become too salty to be used for irrigation. Salt-water intrusion is a significant problem for 17 aquifers located in Baja California, Baja California Sur, Colima, Sonora and Veracruz (see map).

Nearly 60% of the total groundwater extracted is withdrawn from overexploited aquifers. As expected,  the over-exploited aquifers are in the heaviest populated and the most arid areas. Total water extraction exceeds recharge in Mexico City, Monterrey and other large northern metropolitan areas as well as irrigated areas of Sonora, the central northern plateau, the Lerma basin and Baja California.

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Mexico’s water resources and water-related issues are the subject of chapters 6 and 7 of Geo-Mexico: the geography and dynamics of modern Mexico. Ask your library to buy a copy of this handy reference guide to all aspects of Mexico’s geography today! Better yet, order your own copy…

Uxpanapa, an example of forced migration

 Excerpts from Geo-Mexico  Comments Off on Uxpanapa, an example of forced migration
Oct 312011
 

Almost all internal migration in Mexico in recent history has been voluntary. Tens of thousands of rural Mexicans have decided that life might be better somewhere else and have left their farms for the bright lights of the nearest large city. Their motivation is usually economic, but sometimes may be based on educational opportunities or access to health care.

However, not all internal migration has been voluntary. There have been some cases of forced migration, where the inhabitants of a village or area have been made to move away in order to make way for large-scale infrastructure projects such as reservoirs, tourism resorts and hotel complexes.

Since most good dam sites are in remote highland areas, with sparse population, forced migrations due to new dams are relatively rare in Mexico. One good example is when the building of the Cerro de Oro dam in the 1970s in northern Oaxaca, on a tributary of the River Papaloapan, flooded 360 square kilometers (140 square miles) and meant the forced relocation of more than 5000 Chinantec Indians. [Aguilera Reyes] The resettlement plan was one of the most forward-looking of its time. Villagers received compensation for their existing homes, trees and crops, and were offered a choice of possible resettlement sites.

They chose an area of rainforest-covered ridges and valleys near the headwaters of the Rivers Coatzacoalcos and Uxpanapa in the Isthmus of Tehuantepec. With government assistance they built a dozen new villages named, somewhat unimaginatively, Poblado Uno, Poblado Dos, etc. Extensive agricultural support was provided for several seasons, but the plan failed to live up to expectations, in part because its architect, the distinguished Mexican geographer Jorge Tamayo, was killed in a plane crash in 1978.

Many of the area’s young people have migrated (voluntarily) north. The remaining villagers grow ixtle, a fibrous cash crop produced from rainforest bromeliads that can be used for ropes and belts. They are also trying to introduce ecotourism to preserve what is left of their tropical jungle hideout, which has a rich biodiversity, including spider monkeys and jaguars. [Ginsberg]

References:

Aguilera Reyes, S. 2004 “Desarrollo, Población y Uso de los Recursos Naturales en el Valle de Uxpanapa.” Universidad Veracruzana Facultad de Sociología thesis. Xalapa,Veracruz. Marzo 2004.

Ginsberg, S. 2000 Report from Uxpanapa. Can bromeliads save Veracruz’s last rainforest? [6 September 2009]

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This post is an edited excerpt from chapter 25 of Geo-Mexico: the geography and dynamics of modern Mexico. Buy your copy today!

Cultural diffusion: Thousands of students in Mexico receive classes by TV

 Excerpts from Geo-Mexico, Updates to Geo-Mexico  2 Responses »
Oct 222011
 

Mexico’s pioneering “telesecundaria” or “television secondary school” system began back in 1968. It now provides junior high school classes in remote areas, serving about one million students in grades 7 to 9, 17% of the total nationwide enrollment in these grades. Many of the telesecundaria lessons are now available on the Internet, and before long, about 4,500 classes will also be available on a DVD collection.

The geographical network of telesecundarias is truly amazing. In the early 1980s, I came across one high in the mountains in a distant corner of the state of Hidalgo, in a remote Huastec village, beyond even Coca Cola’s delivery routes. A visitor was such a surprise that the entire village turned out to inspect me!

Telesecundaria in Ixcatepec, Hidalgo

Telesecundaria in Ixcatepec, Hidalgo (1983) Photo: Tony Burton

It was that experience that made me realize that Mexicans take education very very seriously. The telesecundaria was perched on the hillside overlooking the village. I later discovered this was a fairly typical example, with three classrooms, rustic restrooms in an outhouse, and a small playground. Most telesecundarias also have a science laboratory and a small library.

The students in a telesecundaria do have a teacher, but this teacher teaches every subject, whereas in a regular junior high, each student will have up to twelve different subject specialists. Every telesecundaria classroom has a television set to receive lessons broadcast by the Education Ministry (SEP) in Mexico City.

Professional Programs

In the early days, lessons were very traditional, and the TV programs were little more than continuous shots of a “talking teacher”. Interestingly, almost all those early lessons were broadcast live. Nowadays, the entire process is much slicker and far more professional. The TV programs are 15 minutes long and feature all kinds of material, including animated graphics and video footage. Watching them, you are unlikely to see the “talking teacher” even for an instant! It takes about 20 days to produce each 15-minute module and costs up to 50,000 dollars. Most programs have a useful life of between five and ten years, depending on the timing of significant changes in subject content and teaching methods.

After students have seen the TV broadcast, the classroom teacher then uses the remaining 45 minutes of each hour to explain the lesson in more detail and to monitor students as they complete related tasks from their special telesecundaria textbooks.

Nationwide satellite transmission of programs began in 1994 (EDUSAT), enabling the coverage to spread far beyond those areas previously served by conventional TV stations. Programs are broadcast daily.

On-line samples

With the advent of the Internet, the telesecundarias are now being revamped as one part of SEP’s “On-line educational TV” (“Televisión educativa en línea“) project. That page has links to currently playing segments of material for various levels, including telesecundaria, and for teachers. (This is also a valuable resource for non-native speakers working to improve their Spanish and/or their knowledge of Mexico.)

Telesecundarias have proved to be an extraordinarily effective way of improving access to, and standards of, junior high education across Mexico. While the “costs of delivery” are estimated to be 16% higher in telesecundarias, on a per student basis, than in regular junior high schools, they are significantly cheaper on a per school basis. This means that some of the nation’s 13,000 or so telesecundarias can function cost-effectively even with only 10 or 12 students in each grade level.

The success of telesecundarias

Are telesecundarias successful? It certainly seems so. An estimated 79.4% of telesecundaria students complete grade 9, compared with an equivalent figure of 78.8% for regular junior highs. In addition, one study has shown that telesecundaria students may start Grade 7 significantly behind other students but generally catch up completely in math and reduce the deficit in language.

The program has been adopted by most Central American countries—Costa Rica, El Salvador, Guatemala, Honduras and Panama—and pilot projects are underway in the USA in California, Colorado, Pennsylvania, Oregon and Florida.

So next time you’re traveling in the wilds of Mexico or Central America, play “I spy” and see how many telesecundarias you can find. Bonus marks should be awarded for any that are outside the normal delivery range of Coca-Cola or Sabritas!

The geography of road transport in Mexico

 Excerpts from Geo-Mexico, Updates to Geo-Mexico  Comments Off on The geography of road transport in Mexico
Oct 202011
 

Mexico’s road network is heavily used, accounting for over 95% of all domestic travel.  On a per person basis, Mexicans travel an average of 4500 km (2800 mi) by road each year.

In this post, we try to answer several general questions relating to the geography of road transport in Mexico.

How many cars are there?

On average there are about seven people per car in Mexico, compared to about six in Argentina, ten in Chile and less than two in the USA and Canada. There are far more cars in urban areas with their many businesses, taxis and wealthy residents. In poor rural parts of southern Mexico, private car ownership is quite rare.

Is there an efficient bus system?

Mexico also has an inter-city bus system that is one of the finest in the world. The nation’s fleet of more than 70,000 inter-city buses enables passengers to amass almost half a trillion passenger-km per year.

Where are Mexico’s vehicles made?

Almost all the vehicles on Mexico’s roads were built in Mexico. Mexico’s automobile-manufacturing sector produces about 2.2 million vehicles a year but the majority of production (about 1.8 million vehicles each year) is for export markets. Mexico is the world’s 9th largest vehicle maker and 6th largest vehicle exporter. In recent years, the relaxation of strict import regulations has resulted in more vehicles being imported into Mexico; many of them are luxury models not currently made in Mexico.

The major international vehicle manufacturers with plants in Mexico include Volkswagen, Ford, Nissan, GM, Renault, Toyota and Mercedes-Benz. Mexican companies include Mastretta, which specializes in sports cars, and DINA, a manufacturer of trucks, buses and coaches.

For more information about vehicle manufacturing in Mexico:

Where are Mexico’s vehicles?

Mexico has about 20 million registered vehicles, about one for every five persons (2005). Which areas have the most and least vehicles? It turns out that the northernmost state, Baja California, has the most with 37 registered vehicles per 100 people. The southernmost states, Chiapas and Oaxaca, have about one sixth as many with 6.6 and 6.9 respectively. In fact there is a very strong statistical relationship between latitude and vehicles (see graph). How can this be?

Scattergraph of latitude and vehicle registrationsWe are not suggesting a direct causal relationship. Many factors are interrelated. First, the states in the north tend to be wealthier; the Spearman rank correlation for GDP/person and latitude is 0.58. Vehicle ownership is closely related to GDP/person (rs = 0.59). Both these correlations are significant at the 99% level.

In addition, northern states are close to the USA, a vehicle-oriented society. However, there are some anomalies to the general pattern. The very wealthy Federal District has 50% more vehicles than would be expected from its latitude alone. States with many migrants, such as Jalisco and Michoacán, also have more vehicles than expected given their latitude. An added complication is that more than a million foreign-plated cars in Mexico (imported temporarily by returning migrants or foreigners) are not included in these figures.

How many road accidents are there in Mexico?

Mexico’s National Council for Accident Prevention estimates that there are 4 million highway accidents each year in Mexico. The latest figures (for 2010) show that there were 24,000 fatalities as a result of these accidents, with 40,000 survivors suffering some lasting incapacity. These figures include some of the 5,000 pedestrians struck by vehicles each year. Traffic accidents are currently the leading cause of death for those aged 5-35 in Mexico, and the second cause of permanent injury for all ages.

Why are there so many accidents?

Driver education plays a major role in road safety. Part of Mexico’s problem is the low budget it allocates each year for road safety—just US$0.40 compared to more than $3.00/person in the USA, more than $7.00/person in Canada and up to $40.00/person in some European countries.

It is no surprise that a high percentage of drivers involved in traffic accidents in Mexico have alcohol in their system. This is one of the reasons why accidents are statistically more frequent in the evenings from Thursday to Saturday. One study reported that as many as 1 in 3 of drivers in Guadalajara was under the influence of alcohol while driving, and 1 in 5 of Mexico City drivers.

Driving without insurance is common in Mexico; according to insurance companies, only 26.5% of Mexico’s 30.9 million vehicles have any insurance.

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Mexico’s Pemex: the government cash cow that environmentalists love to hate

 Excerpts from Geo-Mexico  Comments Off on Mexico’s Pemex: the government cash cow that environmentalists love to hate
Jul 252011
 

Petroleos Mexicanos (Pemex), the giant, state-owned petroleum company, is a symbol of national pride with revenues of over $100 billion in 2008. However, it is cash poor because most of its revenue goes to the government, covering 40% of the national budget. Pemex is $40 billion in debt and its maintenance budget is insufficient to keep its old infrastructure operating safely. About a third of Pemex’s 50,000 km of pipeline is over 30 years old and susceptible to failure.

Environmentalists love to hate Pemex because it has inflicted enormous environmental damage. The June 1979 blowout at the Ixtoc-I drilling rig in the Bay of Campeche resulted in the world’s second largest ever unintentional oil spill: over 450,000 tons, surpassed only by BP’s Deepwater Horizon, but more than ten times the size of the 1989 Exxon Valdez disaster. In November 1984 a series of explosions at a Pemex storage facility in San Juan Ixhuatepec in northern Mexico City started major fires killing about 500 people.

A massive gasoline leak into Guadalajara’s sewers in 1992 resulted in a series of explosions that resulted in over 200 deaths. In recent years numerous smaller, but still fatal, explosions and pipeline failures flooding rivers with oil have brought new attention to Pemex’s environmental damage and failing infrastructure.

cover of "como destruir el paraiso"

It has long been recognized that environmental damage is particularly severe near the conglomeration of Pemex facilities in southern Veracruz near the mouth of the Coatzacoalcos River. The river suffers from chronic heavy petroleum pollution, receiving massive doses periodically when pipelines break. Possibly the only beneficial outcome of the decades of widespread damage caused by Pemex in its principal areas of operation in Veracruz, Tabasco and Campeche was that it prompted the publication in 1983 of Cómo destruir el paraíso (How to destroy Paradise), a book which gave an immense boost to Mexico’s then fledgling environmental movement.

Federal environmental agencies have had only limited success in forcing Pemex to take corrective actions. Pemex recognizes the problems and applies each year for more maintenance funds from the government. The government, however, sets a higher priority on funding exploration since Mexico’s oil reserves are running out. Pemex is fundamental to the Mexican economy but needs investment in maintenance and must become more accountable for its environmental impacts.

Mexico’s environmental issues are analyzed in many chapters of Geo-Mexico: the geography and dynamics of modern Mexico, including chapter 30. Explore the book using Amazon.com’s Look Inside feature and buy your copy today!

The spacing of central places in Mexico

 Excerpts from Geo-Mexico  Comments Off on The spacing of central places in Mexico
Jul 162011
 

Central place theory may work quite well in Mexico in terms of the relative numbers of settlements of different size, but the theory also suggests that those places on the same level of the urban hierarchy should form a distinctive spatial pattern and be roughly equidistant from one another. In essence, this means that each of these central places will be at the center of an approximately equally sized market area, or sphere of influence, well positioned to serve everyone who lives within its limits.

The application of central place theory to Uruapan, Michoacán

The application of central place theory to Uruapan, Michoacán. Credit: Tony Burton / Geo-Mexico; all rights reserved

The map shows the settlements in the western part of the state of Michoacán. The largest city by far is Uruapan (250,000 inhabitants in 2008). Around Uruapan are six fairly large neighboring towns or cities. Each of these settlements has its own corresponding market area. However, even though these six places are roughly equidistant from Uruapan, they turn out to be very different in size. For example, Zamora (240,000) has more than four times the population of Pátzcuaro (53,000). Zamora is bigger because in addition to providing services to a larger, more prosperous, surrounding market area, it also has some manufacturing and is on a railroad line and the original highway between Mexico City and Guadalajara.

In addition, there is no observable regularity in the pattern of settlements of the two smaller sizes—“other towns” and “urban localities”—shown on the map. This is clearly in contradiction to central place theory, but should not really be a surprise. The theory assumes, for the sake of simplicity, that large areas will not have any significant differences in relief or soil fertility and that transport costs will be directly proportional to distance. It also assumes that rural areas have equal population densities and that their residents have similar consumer tastes and purchasing power. In practice, these assumptions are not valid, and some of the anomalies in the pattern of settlements shown on the map can be easily explained. For instance, the areas immediately north of Apatzingán and east of Nueva Italia are very mountainous, far less favorable for farming and settlement than the area north of Uruapan.

The very idea that settlements will be equidistant from one another begs a very important question, pertinent to our earlier discussion of the categories of rural settlements. Should we measure distance only in a spatial sense, in kilometers, or might it be more worthwhile to consider it in terms of the time or monetary cost required to make a particular journey, taking into account the terrain and transportation network?

In summary, central place theory does a good job of explaining the number of central places at each level and the types of services they provide. At the same time, departures from the idealized shape and size of market areas predicted by the theory help to reveal the complexities of Mexico’s physical, human and socio-economic geography.

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The hierarchy of central places in Mexico

 Excerpts from Geo-Mexico  Comments Off on The hierarchy of central places in Mexico
Jul 132011
 

How well does central place theory fit the Mexican situation? In terms of the relative numbers of settlements of different size, it fits quite well. The theory suggests that there will be a regular (geometric) progression between the number of settlements of each successive size. The hierarchy of central places in Mexico is quite similar to that predicted by the theory (see table).

Population sizeNumber of localities or municipalities% of national population
< 2,500184,71423.5
2,500–9,9992,37910.6
10,000–49,99961512.1
50,000–499,99916225.6
500,000–999,9992313.9
1,000,000 +1114.3

At the lowest level in Mexico are a large number of very small centers providing a limited range of goods and services. At this level are small convenience stores (abarrotes or bodegas) selling basic Mexican household goods such as sugar, tortillas, bread, produce, snacks, basic canned goods, candy, eggs, beer, soft drinks, cigarettes, matches and basic toiletries.

Other small stores at this lowest level might sell such things as household cooking and lighting fuels (wood, gas, or kerosene), seed, animal feed, fertilizer and other basic farm inputs. Other services might include a place that buys agricultural production, auto and tire repair shops, and a bus pick-up point. Some of these small centers might also have tortillerías (shops making tortillas), a primary school and a pay phone.

At the next higher level there is enough demand to support everything at the lowest level plus simple bakeries, hardware stores, mini-super markets, electrician/plumbers, welding shops, simple clothiers or dressmakers, beauty salons, basic health care, simple pharmacies, a church, a secondary school, simple eateries, and repair of household electrical items (radios, blenders, TVs). There might be only half or a third as many settlements (places) at this level as at the lowest level.

Central places at this level might also have weekly or periodic markets. Such markets usually occur only one day a week because there is not sufficient threshold demand to support them on a daily basis.

The link is to a map showing the major weekly marketing cycles for the Oaxaca area in southern Mexico. With the exception of Oaxaca city (population 480,000) and Miahuatlán (33,000), all the other towns have populations between 13,000 and 20,000. The merchants at such markets generally carry their wares from village to village on the days of their respective markets. Some local farmers also sell their produce at such markets. These markets give villagers access to a much wider range of goods than might otherwise be possible. Simultaneously, traders maximize their opportunities to make a profit.

Depending on the rural population density and economic demand for particular goods and services in the geographic area, periodic or weekly markets may not exist at this level of the hierarchy in some regions and may only appear at higher levels.

A similar principle applies to a circus (figure 24.4 in Geo-Mexico), which needs access to an even larger threshold population than a weekly market. This is because each individual visitor will not be prepared to travel far to see the show and has little interest in seeing the same acts more than once. Even a very large city will only house enough people to fill the Big Top for a few weeks. The circus’s solution, in central place terms, is to access the combined populations of numerous towns or cities by moving from one to the next, on an annual or biannual itinerary.

As we move up the hierarchy in Mexico, there is enough demand to support everything at the lower levels as well as new services requiring higher levels of threshold demand. These might include doctors, dentists, carpenters, construction supplies, furniture and cabinet makers, bars, restaurants, a Pemex gas station, auto parts stores, and a variety of retail outlets selling such things as stationary and paper products, mobile phones, toys, flowers, plastic ware, and kitchen items. Centers at this level are larger and far fewer in number than the smaller centers at lower levels.

At the next higher level there are even fewer and even larger central places providing such services as appliance sales, jewelry stores, banks, opticians, lawyers, accountants, photographers, preparatory schools, hospitals, hotels, used car and pickup sales, a Coca-Cola bottler, funeral homes, a bus station, a Telmex office, TV and electronics sales, cyber cafes, clothing boutiques and shoe stores.

Further up Mexico’s hierarchy there is enough demand to support higher level services such as: new car and truck sales, TV and radio stations, movie theaters, giant supermarkets, printers, bookstores, dry cleaning, real estate offices and office supply stores. Centers at this level would be fewer in number and have larger geographic market areas.

At the top of the hierarchy are places like Mexico City and Guadalajara, where the demand is sufficient to support the highest level goods and services such as giant modern retail malls, international airlines, convention centers, international hotels, live theater, investment banking, TV studios, multimedia advertising agencies, major universities with medical schools, all types of specialized luxury products, and very specialized professional services such as heart and brain surgeons.

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Central place theory and rural access to central place services

 Excerpts from Geo-Mexico  Comments Off on Central place theory and rural access to central place services
Jul 092011
 

A previous post – The four basic types of rural locality in Mexico – indicates that access to sources of goods, services, markets and opportunities is very important to the economic and social well-being of rural and farm communities. Such sources are called central places and may be a village, a small town, a large town or a city.

Farms in rural areas may still grow some of their own food, but they are far less self-sufficient than they were a century or two ago. In Mexico, farm families are definitely part of the cash economy and buy more of their household needs than they produce on the farm. Items purchased from central places include such goods as sugar, clothing, hardware, farm tools, kitchen utensils, fertilizer, pesticides, hybrid seed, oil or kerosene for lamps, matches, paper products, as well as medicines, soft drinks, beer and cigarettes. Rural areas are also dependent on outside services provided by schools, buses, doctors, dentists, beauticians, mechanics and churches. To pay for these goods and services they are also dependent on markets where they can sell their farm products or their labor to obtain the cash they need to make necessary purchases.

Central place theory

Considerable academic attention has been focused on central places which provide goods and services to their market areas or hinterlands. Walter Christaller analyzed the German rural economy in the 1930s and developed central place theory. The theory provides an idealized description of how goods and services are supplied in rural areas throughout the world. Central place theory describes the spacing and hierarchy of central places by focusing on the threshold demand needed to support specific goods and services, the market areas of central places, and the distances rural people travel to obtain specific goods and services.

According to the theory, every rural region is served by a hierarchy of central places. At the bottom of the hierarchy there are a large number of very small places providing services with very low threshold demands. These very small centers serve the population in the center and a small surrounding rural area.

As one moves up the hierarchy, there are a fewer number of places, providing a wider range of goods and services, and serving a larger market area. This occurs because for a service to be provided efficiently there must be sufficient threshold demand in the center and its surrounding hinterland to support it. For this reason we do not find new car dealers, heart surgeons or ballet schools in every small village. These activities can only survive in large centers where there is sufficient demand.

Rural residents must travel varying distances to centers to obtain needed goods or services. The center may be small or may be large depending on the specific good or service that is needed. Rural residents might have to travel less than a few kilometers to a center at the bottom of the hierarchy to buy basic food stables or to attend primary school. They generally have to travel farther to a higher level center to get more specialized items such as clothing, health services, or secondary schooling. They generally have to travel considerably farther to buy a pickup truck, board an airplane or obtain the services of a heart specialist.

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The four basic types of rural locality in Mexico

 Excerpts from Geo-Mexico  Comments Off on The four basic types of rural locality in Mexico
Jul 062011
 

In a previous post, we looked at why Some rural areas are more rural than others.This post describes each of the four distinct categories of rural areas identified by Mexico’s National Population Council (CONAPO).

Rural localities near cities

This group is defined as localities within five kilometers (3 mi) of cities of at least 15,000 inhabitants. It accounts for 16% of Mexico’s rural population, about four million people. About half of the rural populations of Morelos and Tlaxcala fall into this group.

Some communities in this category are actually part of the suburbanization or urban sprawl process. People have ready access to many city services and opportunities. If they lack mechanical transportation, they can walk to the city in less than an hour.

What are the socioeconomic characteristics of these localities? The data needed to answer this question often are not readily available. Fortunately, CONAPO has classified rural localities in terms of their degree of marginalization, which provides insights into socioeconomic characteristics. Degree of marginalization is defined using indicators of adult educational attainment, housing quality, and income levels.

About 47% of rural, near city residents live in very marginalized localities.3 While this is much higher than it is in urban areas, it is significantly less than other rural areas. Rural areas near cities tend to be more similar to urban areas. By way of comparison, in Mexico as a whole about 19% of the population live in municipalities classified as very marginalized.

Representative characteristics of very marginalized communities include adult populations with illiteracy rates of about 25% and completion of primary school rates of only 56%. Roughly 27% of houses lack piped water, 27% lack indoor toilets, 46% have dirt floors and 64% are overcrowded. These housing indicators are closely correlated with significant health risks. About 15% of houses do not have electricity. Roughly 84% of economically active people make less than twice the minimum wage. Communities matching this description are very different from modern urban Mexico.

At the other end of the spectrum, only about 4% of near city residents live in non-marginalized localities, which we will call “modern”.5 For Mexico as a whole, 53% of the population live in modern municipalities. The figure is 100% for the 33 million people who live in Mexico’s nine urban areas of over one million inhabitants. Levels of marginalization will be discussed more fully in chapter 29.

Rural localities near towns

This category includes localities within three kilometers of towns with between 2,500 and 15,000 residents. About 2.4 million people, or 10% of the rural population, live in such communities. These localities account for about a quarter of the rural population of Morelos and the State of Mexico.

Communities in this category are more rural than communities near cities. They have easy access to goods and opportunities in towns, but lack ready access to a real urban area. About 66% of this group lives in very marginalized communities compared to 47% for the near cities group. Less than 1% of the near towns group live in modern communities.

Rural localities near roads

This large group includes localities within three kilometers (2 mi) of paved roads. Almost 13 million Mexicans, about 54% of the rural population, fall into this category. It accounts for almost 90% of the rural population in Quintana Roo and over 70% in Zacatecas, Yucatán, Campeche, San Luis Potosí, Nuevo León and Coahuila.

This is a relatively important category because almost 14% of Mexico’s total population lives in rural communities near roads. These localities account for 39% of the total population of Zacatecas, and about a third of the total for Hidalgo, Oaxaca and San Luis Potosí. The authors agree to differ as to the reasons for this. One of us believes that the location of paved roads is having an impact on rural settlement patterns. The other believes that rural settlement patterns are having an impact on the location of paved roads! Both viewpoints may be correct with their relative importance depending on the region in question.

While people living in these localities do not have walking access to a city or town, they can relatively easily get to a town or city by bus. Some 69% live in very marginalized communities, while less than 1% live in modern communities. In terms of marginalization, the near roads group is quite similar to the near towns group.

Isolated rural localities

This group includes rural localities that do not fit into any of the other three categories. They are the most rural in that they lack ready access to paved roads, towns or cities. These inaccessible areas are very rarely seen by outsiders. Most urban residents have limited understanding of life in these isolated areas. Communities in this group are among Mexico’s poorest. About 88% of the people in isolated rural localities live in communities classified as very marginalized; less than 1% live in modern communities.

Though data are not available, areas that are within 10 km of a city, town or paved road are likely to be less marginalized than those in more remote locations. Almost five million Mexicans, about 20% of the rural population, live in these communities. Over a million people in Chiapas and about half a million in Oaxaca and Puebla live in isolated localities. The figure for Chiapas represents 29% of the state’s total population. About 16% of the people in Nayarit and Oaxaca and 12% of those in Sinaloa and Guerrero live in isolated areas. Providing needed basic services to these rural Mexicans is a major challenge for these state governments as well as the federal government.

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The availability of water in Mexico

 Excerpts from Geo-Mexico  Comments Off on The availability of water in Mexico
Jul 042011
 

Though parts of northern Mexico are arid, the country as a whole receives an average of 760 mm of precipitation a year (slightly over 30 in). This is a considerable amount, more than that received by either Canada or the USA. However, 73% of Mexico’s rainfall either evaporates directly or or is lost from plants via evapotranspiration. About 25% runs off into rivers and lakes. Only roughly 2% seeps down to recharge subterranean aquifers.

Consumption of water, by sector

Consumption of water, by sector © Tony Burton / Geo-Mexico, 2010; all rights reserved

Availability of water per person is a function of population size and the total amount of water available. Though Mexico gets more rain than the USA or Canada, the availability of water per person in Mexico is only one-twelfth that of Canada and about half that of the USA because Mexico’s population density is far higher. In other words, though each square kilometer in Mexico receives more rain on average, that rain must be divided among more people. Of 177 countries analyzed by the FAO, Mexico ranked 90th in terms of water availability per person. However, if Mexico is divided into two zones, the south would rank 51st and the north would rank 131st.

Within Mexico, the Lerma Basin (between Mexico City and Guadalajara) has only about 1/3rd the national average for water availability, while the very heavily populated Valley of Mexico (containing the Mexico City Metropolitan Area) has only 1/30th the national average.

Mexico’s per person consumption of water is about half that of Canada but with proportionately more allocated to agriculture. Nationally, about 75% of water consumption is used in agriculture, while settlements and industry use about 17% and 8% respectively.

Mexico’s water resources and water-related issues are the subject of chapters 6 and 7 of Geo-Mexico: the geography and dynamics of modern Mexico. Ask your library to buy a copy of this handy reference guide to all aspects of Mexico’s geography today! Better yet, order your own copy…

Some rural areas are more rural then others

 Excerpts from Geo-Mexico, Teaching ideas  Comments Off on Some rural areas are more rural then others
Jul 022011
 

We all recognize that some cities are more urban than others. For example, Mexico City is considered more urban that a town of 20,000. By the same token, some rural communities are more “rural” than others. For example, a small settlement located near a city or along a main road would be considered less rural than an equally sized settlement in a more isolated area.

CONAPO's categories of rural area applied to eastern Michoacán

CONAPO's categories of rural area applied to eastern Michoacán. Credit: Tony Burton; all rights reserved.

The National Population Council (CONAPO) classifies rural localities into four groups based on accessibility to cities, towns and roads. The map shows how these four groups relate to a region in the eastern part of Michoacán state.

Suggested classroom exercise:

Appendix B of Geo-Mexico gives the percentages for each of these four rural groups in each state. What would be the best way to map the figures for the percentages of rural groups in each state?

Are Mexico’s rural areas more diverse than its cities?

 Excerpts from Geo-Mexico  Comments Off on Are Mexico’s rural areas more diverse than its cities?
Jun 302011
 

Which are more diverse: Mexico’s rural areas, or its cities?

At first glance, Mexico’s rural areas are all quite similar in that they lack the characteristics of Mexico’s large cities such as tall buildings, traffic congestion, modern shopping malls, bustling streets, heavy industry and the like. While rural areas are all similar in that they lack urban characteristics, Mexico’s rural areas are actually quite diverse. But is there really more diversity among Mexico’s rural communities than its cities?

The physical form and architecture of cities are essentially independent from their surrounding natural environments. On the other hand, rural settlements tend to be integrated more closely with the natural environment. For example, villages in the arid central plateau tend to be constructed of locally available adobe, which keeps residents relatively cool during the hot afternoons and warm during the colder nights. In the tropical parts of Mexico, rural settlements tend to be built with locally available tropical materials which keep the rain out, but let air breezes through to mediate the hot tropical climate.

Rural settlements all tend to rely heavily on farming as the basic economic activity. The surrounding natural environment essentially dictates the type of farming that is practiced. Obviously, farmers in the central plateau cannot successfully grow bananas, sugarcane and other tropical products requiring lots of water. However, varieties of corn are grown virtually everywhere in Mexico.

The social characteristics of Mexico’s rural areas are also very diverse compared to the cities. In general Mexican cities are quite similar from a social perspective. Social customs and mores, as well as social classes, are relatively constant from one city to the next. Spanish is the overwhelmingly dominant language in the cities. Rural communities in various parts of the country often have different social mores and customs. Communication in some rural areas is largely, if not almost exclusively, in local indigenous languages:

The diversity of Mexico’s almost 200,000 rural localities should not be confused with the relative homogeneity within any given rural community.

In conclusion, while diversity between rural areas may be greater than that between cities, there is usually far more diversity within a Mexican city than within any given rural community.

Are Mexico’s large cities growing faster than small cities?

 Excerpts from Geo-Mexico  Comments Off on Are Mexico’s large cities growing faster than small cities?
Jun 232011
 

Aside from intra-urban moves (ie. those made within a city or town), the major focus of migration in Mexico has shifted from the largest cities to the medium cities (those with a population under one million). Medium cities, such as Mérida, San Luis Potosí, Querétaro and Hermosillo, attracted over 1.6 million new migrants compared to only about 1.3 million for the largest cities. The net migration gain of medium cities was almost 370,000, nearly twice that of the nine largest cities. The new focus of migration on medium cities rather than largest urban areas was stimulated by policies to shift growth away from Mexico City. This shift should help relieve the growing congestion in Mexico City and the other large cities.

Migration between municipalities, 1995-2000, by settlement size
Migration between municipalities, 1995-2000, by settlement size. Credit: Tony Burton; all rights reserved

The pattern of migration from small towns and rural areas to urban municipalities continued throughout the 20th century and into the 21st century. Between 1995 and 2000 over 1.7 million migrants left small towns and rural areas (see diagram). Where did these migrants go? Over 60% went to cities of over 100,000, which is not surprising because these cities have more dynamic economies with more employment opportunities. What is a bit surprising is that a full 27% moved to other small towns and rural areas. Many of these moves were to new corporate agricultural developments in the north. Personal and family factors were also important.

Rural areas and small towns attracted almost 1.2 million migrants during the five year period. Over 60% came from cities of over 100,000, while almost 40% came from other towns and rural areas. Many of these moves were undoubtedly earlier migrants returning to their hometowns. The net migration loss of over half a million represented only about 1.6% of the population for the five year period. This is only about one eighth of the natural population increase in these areas. In summary, though small municipalities are experiencing relatively large rates of out-migration, they are also attracting many migrants. Their relatively low rates of net migration loss mean that Mexico should continue to have a substantial rural population for the next several decades.

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This post is an excerpt from chapter 25 of Geo-Mexico: the geography and dynamics of modern Mexico. Buy your copy today, and learn more about Mexico’s fascinating geography. The more knowledge you acquire, the more pleasure you will derive from your next trip to Mexico!

The internet in Mexico: is there a digital divide?

 Excerpts from Geo-Mexico  1 Response »
Jun 182011
 

ITESM, a university based in Monterrey, established Mexico’s first internet connection in 1989. Other universities soon followed. In the late 1990s Telmex started to provide internet service to businesses and the general public. Other providers entered the market but by 2005 Telmex still had about 80% of the market.

Public access via internet cafes is relatively inexpensive. With computers in many schools and cyber cafes in most Mexican towns, about 21% of Mexicans used the internet in 2007. This is relatively low compared to 94% in South Korea, 73% in Canada and the USA, 27% in Peru, 35% in Brazil and 26% in Argentina. Though Mexico is ahead of China (16%), Guatemala (10%) and India and Nigeria (7%), it is still lagging in internet use relative to its overall level of development.

An impressive three-quarters of Mexico’s personal computer internet connections are broadband. Internet use is highest in urban centers but is making steady inroads into rural areas. The highest usage is among 12- to 18-year-olds, with slightly more male users than female. However, less than a third of those in this group use the internet. Just under half of internet use is in the home, the rest is in schools, offices, public centers or cybercafes. About 44% of all users visit the internet for educational purposes, 40% for e-mail, 35% for general information, and 21% for online telephoning (VOIP). The internet is having an enormous impact on Mexican society.

Digital divide map

Internet traffic flows Credit: Stephen Eick, Bell Labs / Visual Insights (www.visualinsights.com)

The digital divide

Overall, just how well does Mexico do in terms of the digital divide? The Digital Access Index (DAI) is a compound index assessing the level of information and communications technologies (ICTs) that a country possesses. The DAI combines variables measuring infrastructure, affordability, literacy and educational level, the availability of broadband, international internet bandwidth per person and internet usage. Sweden placed highest in 2002 with a score of 0.85 out of a maximum possible score of 1.0. Canada and the USA were in equal 10th place.

Mexico (index: 0.50) placed a lowly 65th of the 180 countries in the rankings, level with Brazil but well ahead of China (0.43). Though digital communications in Mexico are expanding rapidly, Mexico lags behind rival countries in these important technologies. This could possibly hamper Mexico’s future ability to compete economically in the increasingly flat world of free trade.

There are some encouraging signs, though, that Mexico is catching up. For example, data for 2008 show that it has become the country with the 8th highest number of internet hosts, the services which provide access to internet servers.

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Want to know what it feels like on the wrong side of the Digital Divide? Try the ICTP Digital Divide Simulator!

The text of this post is an excerpt from chapter 18 of Geo-Mexico: the geography and dynamics of modern Mexico. Buy your copy today, and learn more about Mexico’s fascinating geography. The more knowledge you acquire, the more pleasure you will derive from your next trip to Mexico!

How ecological is ecotourism in Mexico?

 Excerpts from Geo-Mexico  Comments Off on How ecological is ecotourism in Mexico?
Jun 162011
 

Ecotourism is often touted as one solution to many of the potential woes associated with conventional resort tourism. It should come as no surprise to find that Mexico has embraced ecotourism: Mexico’s biodiversity is phenomenal. It is one of the five most important countries in the world in terms of biodiversity:

To be ecologically successful, ecotourism probably has to be small-scale. Constructing the infrastructure necessary for large-scale coastal ecotourism projects often involves the destruction of highly productive (in ecological terms) wetlands, including tropical mangroves. These ecosystems play a vital role in helping preserve biodiversity and their destruction has serious long-term economic implications for fishing, port and marina access, coastline preservation and beach-based tourism.

Marine biodiversity

Mangroves (pictured on the right of the image) are especially vulnerable, with an undeserved reputation for being impenetrable thickets harboring noxious insects and reptiles. Mangroves sequester carbon and help reduce the organic content of water. Their roots bind unstable coasts, preventing erosion and acting as a natural barrier against hurricanes. They are important breeding, shelter and feeding places for fish, crustaceans and birds as well as being a source of charcoal, firewood, wood and roofing materials. They offer economic opportunities of fishing for shrimp, mollusk, fish and crustaceans.

In the year 2000, the total area of mangroves along Mexican coasts was estimated at 880,000 hectares (2.2 million acres), approximately two-thirds on the Atlantic and Caribbean coasts, and one-third on the Pacific. The annual loss of mangroves is estimated to be between 2.5% and 5% of this area. Even with the lower rate of loss, by 2025 mangroves will occupy only half of their 2000 area. In 2007 Mexico enacted federal legislation to protect existing mangroves.

The unique habitats of coral reefs are also at risk. Mexico has important zones of coral from the Baja California Peninsula and Sea of Cortés in the north to Cozumel Island and Chinchorro Bank in the south. The latter area is the northernmost extension of the Meso-American Barrier Reef system which is the world’s second largest reef system after Australia’s Barrier Reef. Marine pollution, overfishing and tourism have all hastened the decline of coral reefs,though many areas are now protected.

Even animal migrations are considered at risk. Some studies have shown that the number of tourists viewing the whale migrations off the coast of Baja California, for instance, is already having an adverse effect on the whales’ breeding habits.

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This is an excerpt from chapter 19 of Geo-Mexico: the geography and dynamics of modern Mexico. Buy your copy today, and learn more about Mexico’s fascinating geography. The more knowledge you acquire, the more pleasure you will derive from your next trip to Mexico!

Two examples of trans-border air pollution on the Mexico-USA border

 Excerpts from Geo-Mexico, Updates to Geo-Mexico  Comments Off on Two examples of trans-border air pollution on the Mexico-USA border
May 262011
 

Poor air quality is known to have significant economic and social impacts, including adverse health risks and a lower quality of life. In this post, we examine two examples of trans-border air pollution. We analyze the causes of poor air quality, and describe the strategies being adopted on either side of the Mexico-USA border to improve air quality.

Does air pollution from maquiladoras in Ciudad Juárez affect people’s health?

The worst air pollution along the USA–Mexico border is in Ciudad Juárez in Chihuahua, located across the Río Grande from the city of El Paso in Texas. It is often claimed that this is because of Mexican authorities’ poor enforcement of environmental laws and the high number of maquiladora firms operating in the city.

Mexico-USA border traffic in Ciudad Juárez

Mexico-USA border traffic in Ciudad Juárez

Air pollution does adversely affect the health of Ciudad Juárez’s 1.4 million residents, resulting in a higher incidence of respiratory diseases and premature mortality. However, most of the pollutants related to these health issues do not come from the 300 or so maquiladora factories but from dirt roads, vehicles and family-run brick kilns. Industry, including the brick kilns, accounts for only 17% of total sulfur dioxide emissions, and less than 1% of total particulate emissions. Services account for 44% of the sulfur dioxide emissions, and transport a further 38%. Most particulates came from unpaved roads (65% of the total) and from wind-blown soil erosion (31%). Almost all the carbon monoxide (99%) and nitrogen oxide (92%) added to the air came from transportation. (Blackman, A., Batz, M. and Evans, D. 2004 “Maquiladoras, Air Pollution, and Human Health in Ciudad Juárez and El Paso. April 2003, updated July 2004.”)

Socio-economically poor areas are more affected by bad air quality than richer areas, but this is due to the precise location of the small-scale brick kilns, which have no pollution controls, rather than to the locations of maquiladora plants. Most of the city’s 350 brick kilns are in densely populated low-income residential neighborhoods such as Anapra, Division del Norte, Fronteriza Baja and Waterfill.

When the kilns were first built, these areas were on the perimeter of the city, but they have since been enveloped by urban sprawl. The health damages arising from the brick kilns are estimated at almost $50 million a year in Ciudad Juárez and an additional $13.4 million a year in El Paso.

How are the cross-border twin cities of Nogales (Sonora) and Nogales (Arizona) trying to improve their air quality?

Further west, the border cities of Ambos Nogales (Both Nogales) share many of the same air quality issues as Ciudad Juárez. Nogales in Sonora has a population of about 250,000, more than ten times that of its cross-border twin in Arizona. Inevitably (given the size differential) most of the pollution, including dust and vehicle emissions, comes from south of the border. Air quality is also adversely impacted by natural hazards such as wildfires in the region. The air in Nogales, Arizona, regularly fails to meet the US Environmental Protection Agency’s limits for coarse particulate (PM10) pollution.

However, now, according to a recent news report, steps are being taken to ameliorate the air pollution in Ambos Nogales by authorities either side of the border.

On the Mexican side, reliable air quality monitoring systems are being installed, with the financial help of international agencies. The Sonoran state government has started a priority program to pave dirt roads in the vicinity of Nogales, responsible for an estimated 9,000 metric tons of dust each year. In the next phase, tighter controls are needed on factory emissions and on the burning of waste.

On the US side, the Arizona Department of Environmental Quality is trying an innovative approach, using federal funds to pay Mexican truck owners to replace their old, leaky mufflers with state-of-the-art catalytic converters. Each conversion costs about $1600. The program should eventually reduce harmful emissions from the particle-spewing diesel-burning trucks by 30%. The next item on the agenda for the US side should be to reduce the waiting times for all trucks crossing the border, so that emissions are further reduced.

We will look at the success (or failure) of these strategies to ameliorate trans-border air pollution in a future post.

Attempts to provide drainage for Mexico City date back to Aztec times

 Excerpts from Geo-Mexico, Mexico's geography in the Press  Comments Off on Attempts to provide drainage for Mexico City date back to Aztec times
Apr 262011
 

An old joke relates how engineers initially rejoiced at successfully draining the former lake on which Mexico City was built (something the Aztecs had tried, but failed to achieve), only to discover that the city now lacked any reliable source of fresh water for its inhabitants (something the Aztecs had successfully managed by building a system of aqueducts).

Water has been a major issue for Mexico City since it was founded almost 700 years ago. Civil engineering works by the Aztecs included causeways and aqueducts connecting their island capital to the mainland as well as lengthy dikes separating the fresh water lakes from the brackish Lake Texcoco which surrounded the city.

The Spaniards did not maintain the Aztec civil works, deforested the surrounding hillsides, and started filling Lake Texcoco. This contributed to major flooding in 1555, 1580, 1604. The city was actually underwater (continuously!) from 1629–1634. During this period the Spaniards invested in several flood control efforts, but they were not successful. In 1788 they started construction of a massive canal to connect the basin to rivers north of the city flowing to the Gulf of Mexico. The open canal, which was up to 30 m (100 ft) deep in places, provided flood relief, but did not completely solve the problem, and flooding continued.

In the mid-1850s the government approved another massive flood relief scheme. Construction of the Gran Canal was delayed by numerous political and financial problems; it was not completed until 1900. The 58 km (36 mi) long canal included a 10 km tunnel, and carried lake water, storm water and sewage north to the Río Salado and eventually to the Gulf of Mexico. The scheme successfully drained most of the basin lakes, but summer flooding continued to be a problem for decades.

Mexico’s deep drainage system (drenaje profundo) was completed in the 1970s. It relies on a 68-km-long central tunnel (Emisor Central) which has a maximum depth of 250 meters below the surface. Built to allow for a flow of 170 cubic meters/second, subsurface subsidence under Mexico City had reduced its maximum capacity to barely 15 cubic meters/second by 2008.

Paradoxically for a city originally built on a lake and which experiences regular summer floods, Mexico City is desperately short of drinking water. The drilling of wells to obtain potable water from the aquifer under Mexico City is one of the main reasons for the ground subsidence which has reduced the effectiveness of the deep drainage system.

Many parts of Mexico City still experience serious drainage problems every rainy season. During the long dry season, many street drains plug with garbage (especially impermeable plastic bags). City motorists dread the first heavy rains of the year since much of the rainwater which falls is unable to find its way underground and backs up from blocked drains. City authorities have an annual campaign to try to clear all drains before the first rains, but are never completely successful.

Since 2007, jointly agreed programs to maintain and renovate the deep drainage system have been undertaken each year during the dry season by Mexico City and the administrations of adjoining states, in an effort to reduce the metropolitan area’s serious flood hazard. In the first four years (2007-2010), more than 42 km of tunnels have been renovated. The 2010-11 season of repairs to the drenaje profundo will be completed before the start of the rainy season (usually in late May or early June), according to city mayor Marcelo Ebrard.

Why are some parts of Mexico City sinking into the old lakebed?

How do El Niño events affect Mexico?

 Excerpts from Geo-Mexico  Comments Off on How do El Niño events affect Mexico?
Apr 112011
 

La Niña and El Niño are two major periodic disturbances to the normal oceanic and atmospheric circulation patterns over the Pacific Ocean which have widespread effects around the world. The normal circulation in the equatorial Pacific (the Walker circulation cell) results from a low pressure area over the western Pacific (due to warm surface ocean temperatures) and a high pressure area over the eastern Pacific (due to the upwelling of cold ocean water off the coast of Ecuador). Surface trade winds blow from east to west, while high altitude air flow is from west to east.

A La Niña event is an intensification of the normal Walker cell. This results in warmer and drier conditions than normal, rarely with serious consequences for Mexico.

However, during an El Niño Southern Oscillation (ENSO) event, the Walker circulation pattern is essentially reversed. Early in the year, warm ocean water extends much further east, causing warm moist air to rise off the coast of South and Central America, bringing heavy rainfall to areas along the west coast of Mexico. The El Niño in 1998 raised the temperature of water off Mexico’s Pacific coast by some 3° to 5°C (6° to 9°F) and also increased the humidity considerably. Historically, ENSO events have occurred every four to seven years, but their frequency may now be increasing.

The effects of an ENSO event are also felt on the Gulf coast. The low pressure area resulting from the air rising off the western coast causes air from further east to be dragged across Mexico. This means that more cold fronts or nortes enter north and central Mexico. Winter precipitation in these areas increases significantly, especially in the north, and temperatures are much cooler than usual. Flooding can result in coastal areas. ENSO effects are also felt in other parts of the world.

In Mexico, ENSO events not only affect winter precipitation but also summer precipitation, which is more critical for farmers. This is because they push the equatorial Intertropical Convergence Zone (ITCZ), where the north-east and south-east trade winds meet, further south. This reduces the convective activity and rainfall in Mexico’s central highlands. Furthermore, this may reduce cloud cover and therefore increase solar radiation and evapotranspiration, making the ground even drier.

In summary, subsistence corn (maize) farmers find that their cooler, wetter winter than normal is immediately followed by a hotter and drier summer growing season. This can have disastrous consequences for their food security. The rapid onset of changed conditions does not allow much time for adequate adjustments to be made to their choice of crops or farming methods.

Historical analysis combined with greater climatological understanding shows that many of the worst droughts and floods in Mexico have been associated with either ENSO events or with the related Pacific-North American Oscillation. Perhaps 65% of the variability of Mexican climate results from changes in these large-scale circulations.

The naughty nortes of Mexico

 Excerpts from Geo-Mexico  Comments Off on The naughty nortes of Mexico
Mar 292011
 

Mid-latitude storms known as nortes (northers) disturb the normal weather patterns up to 20 times a year during winter, from November to March. They occur when northern polar air moves south into northern and central Mexico.

They bring low pressure (cyclonic) conditions, heralded by the arrival of a cold front. The polar air displaces the warmer surface air, forcing it to rise as the cool air pushes its way underneath. At the surface, a sudden drop in temperature and the advent of cold winds marks the passage of the front, followed by several days of overcast skies with light rains or drizzle, onomatopoeically called chipichipis in some areas.

Rains from nortes are heavier on the northern or eastern sides of mountains where the cool air is forced to rise. As the front passes, the temperature can drop by 5–8 degrees C (9–14 degrees F) in a few hours.

From an agricultural perspective these rains are a welcome sight for farmers, helping to improve grazing land and reduce the chances of wind-blown soil erosion. However, the winds can play havoc with shipping in the Gulf of Mexico and result in ports being temporarily closed. Veracruz and Tampico are regularly affected.

Overfishing in Mexico’s Sea of Cortés (Gulf of California)

 Excerpts from Geo-Mexico  Comments Off on Overfishing in Mexico’s Sea of Cortés (Gulf of California)
Mar 032011
 

The Sea of Cortés (Gulf of California) is one of the world’s top five seas in terms of ecological productivity and biological diversity. The region is world famous for its recreational sports fishing.

Background to the region’s wetlands

Among rivers feeding the Sea of Cortés are the Colorado, Fuerte and Yaqui. Its coast includes more than 300 estuaries and other wetlands, of which the delta of the Colorado River is especially important. The vast reduction in the Colorado’s flow has negatively impacted wetlands and fisheries.

These wetlands are also threatened by the development of marinas, resorts and aquaculture, especially shrimp farms. The plant and animal communities in these wetlands provide a constant supply of nutrients which support large numbers of fish and marine mammals. These include the humpback whale, California gray whale, blue whale, fin whale, sperm whale and the leatherback sea turtle.

Wetland degradation and declining fish stocks have had inevitable consequences on many marine mammals. Concern over endangered mammals such as the vaquita porpoise, which is endemic to the area and was being taken as by catch in gill nets, led to the establishment of the Biosphere Reserve of the Upper Gulf of California and Delta of the Colorado River in 1993.

The Biosphere Reserve aims to protect breeding grounds and conserve endangered species, including the vaquita, the totoaba, the desert pupfish and the Yuma clapper rail. This was the first marine reserve established in Mexico; several other marine protected areas has since been established on Mexico’s other coasts.

Did changes in technology hasten the decline of commercial fishing?

In the Sea of Cortés, changes in technology, coupled with high demand for fish (especially in Japan), and greed, help to explain the demise of fish stocks.

Commercial shrimp fishing started here in the 1940s. The introduction of outboard motors in the 1970s allowed small fiberglass boats (pangas) to travel further afield in search of fish. Up to 20,000 pangas using gill nets had an immediate adverse impact on fish stocks, with large decreases in roosterfish, yellowtail and sierra mackerel.

In the 1980s, as the sardine stocks close to Guaymas had been depleted, new sardine boats were built with refrigeration facilities which allowed them to catch sardines further offshore, in their feeding grounds near Midriff Island.

In the 1990s a longline fishing fleet began to operate out of Ensenada. Licensed boats were required to fish beyond a non-fishing zone extending 80 km (50 mi) from the coast. A single longline boat may have 5 km (3 mi) of line with 600 to 700 baited hooks in total. The swordfish populations outside the protected zone were quickly depleted, leading fishing boat owners to apply for permits to catch shark inside the 80-km limits.

The Sea of Cortés faces numerous pressures. Decades of commercial overfishing are causing a total collapse of fish stocks. As late as 1993, the area, less than 5% of all Mexico’s territorial waters, produced about 75% of the nation’s total fish catch of 1.5 million metric tons; however, by some estimates, fish populations have declined by 90% since.

What are the solutions?

Reversing decades of overfishing requires more effective enforcement of fishing regulations, especially the 80-km zone of no commercial fishing; vessel monitoring systems; a ban on the use of gill nets; and a prohibition on the catch of certain fish such as bluefin tuna.

Fish farming may be a viable alternative and several commercial tuna farms, where wild tuna are raised in near-shore pens, have been established in Baja California but more research on the ecological pros and cons of establishing such farms is urgently needed.

In our next post, we will take a closer look at some recent research connected to the restoration of fish stocks in this region.

Fishing in Mexico is analyzed in chapter 15 of Geo-Mexico: the geography and dynamics of modern Mexico. Ask your library to buy a copy of this handy reference guide to all aspects of Mexico’s geography today! Better yet, order your own copy…

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