M. Caballero Deloya
Dr Miguel Caballero Deloya is the Chief Research Officer of the Instituto Nacional de Investigaciones Forestales (National Forestry Research Institute), Mexico.
Mexico City has often been described as one of the world's most polluted cities. There is much to support this claim. Greater Mexico City has a population of 17 million and there is a daily influx of about 1000 new inhabitants. There are 2.9 million automobiles in the area, most of them old and poorly maintained. There are approximately 30000 industrial enterprises (Secretariat of Urban Development and Ecology, 1986). Wind circulation is very poor, favouring the formation of thermal inversion layers during the winter and the constant presence of particulate air pollutants. Against this background, this article considers the current state of urban forestry in Mexico City and its potential to reduce the harmful effects of environmental decline as well as making a number of suggestions for future action to help realize this potential.
Metropolitan Mexico City is the largest and most important metropolitan area in Mexico. The country is very centralized and Mexico City is the political, economic, social and cultural heart of the republic. The city covers an area of 1499 km2 and it lies at an elevation of 2240 m.
The climate is subtropical montane, temperate and semi-arid, with no clearly defined winter (Department of the Federal District, 1975). The average temperature is 15-16°C and ranges from a maximum of 30°C in the summer to occasional drops below freezing point during December and January. Mean annual rainfall is 700 mm and the rainy season is May through October (Department of the Federal District, 1975).
Mexico City has great historical value for the Mexican people. It was here that the "Mexica" or Aztec culture originated. The capital of this civilization, Greater Tenochtitlán, was founded in 1325 and, after the Spanish conquest in 1521, the capital of "New Spain" was later built on this same site. When Mexico gained its independence in 1824, Congress declared this metropolis the official seat of the country's government.
During the colonial period, trees ware planted in the courtyards and outer grounds of churches
Before the arrival of the Spanish, Tenochtitlán was an indigenous settlement with a population of 300000. Vast garden areas were planted in the city and nearby areas such as Chapultepec, Ixtapalapa, and Xochimilco (Benavides Meza, 1992). The gardens were open and informal in design and many different varieties of trees and shrubs were grown. The first examples of the topiary art in America were found in Tenochtitlán and other places in Mexico (De Herrera, 1980).
Informal private trees planted in a Mexico City suburb
The conquistadors destroyed Tenochtitlán and built the Spanish colony's capital in its place. During the colonial period, gardens were planted in the courtyards and outer grounds of the various churches built at that time. The Spanish introduced the "Arab garden" concept to Mexico City, with gardens set in the inner courtyards of homes and in public squares (Caballero Deloya, 1986). In Mexico City and other towns of New Spain, these squares were given regular geometric patterns. Lovely gardens with trees and flowers were planted and the squares became the favourite recreational areas and meeting places for all social classes. An example is Alameda Central, one of the most traditional and historic of all Mexico's city parks, which was built in 1529. One year later, another site with a long tradition, the "Forest of Chapultepec", was declared a public park. Chapultepec Park today is the park most visited by residents of the capital.
During the colonial period, trees were also planted along the major avenues and promenades (Department of the Federal District, 1985).
Liquidambar styraciflua is one of the species commonly used in urban forestry in Mexico City
Mexico's period of independence began in 1821, with frequent bouts of armed conflict monopolizing the few available resources and the attention of Mexican authorities and citizens alike for a number of years. Nonetheless, they did manage to maintain the existing gardens and parks and, occasionally, to plant trees in new gardens and promenades (Benavides Meza, 1992). There was French military intervention in Mexico from 1864 to 1867 at which time new park and garden design concepts were introduced. The configuration adopted for the green areas was very formal and geometric, as was the remodelled Alameda Central, an influence which persisted up to the turn of the century (Caballero Deloya, 1986).
Mexico City has experienced an overwhelming growth rate in the twentieth century, with the highest peaks occurring in recent decades. It now has the largest human concentration in the world. This population explosion has been fuelled by intensive, steady and systematic rural emigration, of which the fundamental cause is the deep-seated socio-economic imbalance between urban society and the Mexican countryside: the rural population has been extremely alienated for centuries. The growth in population has not been matched by an increase in green space. In 1794, 14 percent of the city consisted of green areas but, by 1910, the proportion had dropped to 2.8 percent (De Quevedo, 1935). Today, the total urban green area is estimated to be about 33.1 km2 or only 2.2 percent of the entire metropolitan area (Benavides Meza, 1992). In terms of per caput green space, Mexico City has only 1.94 m2 per inhabitant, far below the 9 m2 recommended by the World Health Organization.
The enormous environmental problems afflicting Mexico City and some the country's other big metropolitan areas underscore the impelling need to intensify Mexico's urban forestry programme. Such efforts cannot solve all the complex problems of these cities. However, they can be quite effective in reducing the harmful effects of urban environmental decline and in making the life of city dwellers more rewarding.
The fundamental goals of the urban forestry programme in Mexico City today are:
· To help mitigate the effects of severe air pollution in the metropolitan area. It is reported that "the smog that hangs over Mexico City every day like a grey cloak is caused by an average of 650 tonnes of particulate contaminants floating in the air" (Secretariat of Urban Development and Ecology, 1986).
· To establish more open-air recreational areas for the long-suffering population of the capital. It is important to point out here that the big metropolitan parks, including Chapultepec, Desierto de los Leones, Parque Hundido, Deer Park and Cerro de la Estrella, have come to be very important for sports and other forms of recreation.
· To give the city a better, more welcoming appearance in the eyes of its population.
Urban forestry needs in the major metropolitan area differ according to the prevailing situation in specific zones, which can be divided into areas of historic interest, areas of planned urban development and poor, unplanned suburban areas.
A lack of labour and financial resources results in the presence of many dead street trees
Areas of historic interest
These comprise the oldest sections of the city where buildings, churches, parks and monuments have become relics of the past. These are traditionally the areas of greatest interest to tourists. The sites are commonly graced by the presence of big trees and lovely gardens in central squares.
Planned urban development
Various land subdivision and development agencies have arisen in recent decades. They have expanded the metropolitan area by urbanizing new land, particularly in the southern and western parts of the city. A few of these urban development projects have given attention to the establishment of green areas, adopting modern designs that imitate patterns developed in North
American cities. Unfortunately, the high cost of these areas limits access to a small group of affluent families. By contrast, most planned urban development has -been in the form of massive constructions designed to offer low-cost housing on small sites in working class areas. The outlook for urban reforestation under such conditions is very poor and reflects major limitations.
Various parts of the city's eastern suburbs, within the State of Mexico, have borne the brunt of the waves of rural migration to the city. The form this process has taken (occupation of land that is utterly devoid of urban infrastructure) has been much too anarchical to allow any planning in terms of green areas. Additionally, the high population density of these areas has left little margin for implementing appropriate urban reforestation programmes. Some of the settlers, concerned about the need for green areas, have made personal efforts to plant trees, but these have been haphazard initiatives, lacking any concrete strategy or plan (Caballero Deloya, 1986). Virtually no technical assistance has been provided by government authorities. The people concerned have not been able to obtain guidance on what kind of tree to use, when to plant, how to prepare the planting hole and place the tree in it, what kind of care the tree needs and so forth.
Given the enormous size of Mexico City and the complexity of its problems, city administration is split into 16 political subdistricts which are highly heterogeneous in terms of size, population, social and economic problems and degree of urbanization. For example, two subdistricts have populations of less than 200000 whereas two others have populations of more than one million. Each subdistrict has a parks and gardens office which has a modest amount of equipment, tools and staff specifically for urban reforestation. The responsibilities of these offices include: the replacement of ailing and dead trees; tree maintenance work (pruning and watering); sanitation work (application of insecticides and fungicides); and the creation of new green areas.
Financial limitations have led to priority being placed on the first three of these actions, as the fourth is heavily dependent on the availability of additional resources. Moreover, maintenance work in urban wooded areas is mainly confined to downtown Mexico City and to the historic or residential neighbourhoods. Not much attention has been given to poor neighbourhoods or suburbs.
Overall, the estimated survival rate for trees planted in Mexico City is only 40 to 50 percent. The major causes of death are:
· The widespread and severe air pollution affecting the city. The worst damage is seen in trees planted along or near major traffic arteries. An evaluation of the present status of the pine species (Pinus radiata) used for the reforestation of Mexico City showed that 75 percent of the trees surveyed exhibited serious symptoms of decline, which took the form of twisted boles, hyperfoliation and resinosis. Eighty percent of the specimens in the survey also showed signs of dwarfism (Nieto de Pascual, 1988).
· The use of unsuitable species and inappropriate management techniques. Planning problems, scant resources and other circumstances have created a situation where much of the available seedling production is not suitable for urban reforestation.
· Vandalism, particularly in the most socially marginal areas.
Urban reforestation in suburban Mexico City
Mexican society is becoming more aware of the need to promote reforestation and the care of urban trees as a vital means of ensuring urban well-being and even urban survival. This increasing awareness may be seen in:
· The establishment of the Municipal Forest Committees. Promoted by the Secretariat of Agriculture and Water Resources, these committees are being set up in every state in the country. They promote direct citizen participation in various forestry objectives, including the establishment of as many urban green areas as possible.
· The proliferation of ecological groups which use the media to press for the expansion of urban forestry effort - the Movimiento Ecologista Mexicano (MEM) is one example.
· Specific citizens' groups that have been organized for the purpose of urban forest renewal. One is the "Friends of Chapultepec Forest" which, through a recent national campaign, raised funds to restore the most visited city park in the capital.
· The creation in 1982 of a Secretariat of State for Mexico's urban and environmental problems. This was incorporated in the new Secretariat for Social Development (SEDESOL), set up in 1992.
Federal District authorities are convinced that the city reforestation campaign cannot hope to succeed without the dynamic participation of the city's inhabitants. Intensive campaigns have been carried out in the last few years just for the purpose of enlisting such participation. The 1990 campaign, under the theme "A tree for every family", achieved the planting of more than 1800000 saplings in the 16 political subdistricts. Reforestation has become a strategic national banner, rallying the entire society and the various ranks of government around a common cause. The Secretariat of Public Education promotes this cause through schoolchildren. The Secretariat of Agriculture offers saplings free of charge and promotes their use at the national level. The Mexican Army participates every year in national reforestation. The Secretariat for Social Development provides resources and supports urban and rural community reforestation efforts while ecological groups and urban and rural organizations promote various forms of participation. This is a vast but disjointed effort and there are a number of major gaps. If this highly important task is to be successful, the following activities will be necessary:
· the preparation and responsible implementation of medium- and long-term master plans for urban forestry;
· the coordination of independent and disjointed reforestation efforts by the various institutions and subagencies. In Mexico City, the political subdistricts of the Department of the Federal District should cooperate among themselves and with other organizations;
· seed collection and sapling production in nurseries should be planned for the medium and long term in accordance with the future needs and programmes of reforestation contained in the master plan;
· workers in the Department of the Federal District and state agencies responsible for urban reforestation should be trained in the use of modern procedures and equipment;
· teams of professional experts should be formed and made responsible for the success of the master plans;
· permanent awareness-building and education programmes should be developed for city populations, concerning the basic principles of urban forestry and, particularly, aspects dealing with how plants affect human well-being; reforestation techniques; and the care of urban trees.
Recently, the Governments of Mexico City and two nearby States of Mexico and Morelos signed two major agreements; one with the Inter-American Development Bank (IDB) and another with the Government of Japan. Through these agreements, the city will receive a substantial international loan to finance an intensive reforestation campaign in the urban area (the IDB loan), and in the suburban part of the Federal District and the States of Mexico and Morelos (the Japanese loan). Part of the loan will be channelled towards training, consultancy and the purchase of modern equipment There is great optimism about the achievements these international projects are expected to produce.
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