Maya glyph

by Les Beletsky

Index: Major Threats and Conservation Record | Conservation Programs and Ecotourism | Biosphere Reserves | Ecotourism | Ejidos and Ecotourism

Major Threats and Conservation Record
Mexico is a huge country (one of the world’s 15 largest) with a big population (96 million in 1996) growing at a fast pace (between 2% and 3% annually, due to double within 24 to 34 years). There are major environmental threats, chiefly destruction of natural habitats, and the country has had, until very recently, a poor environmental record and outlook. Suffering from widespread poverty, governmental neglect and corruption, and little organized local interest in conservation, Mexico for most of its history has been a state where business and agricultural interests held nearly absolute power over development decisions and the uses of natural resources. Economic growth, at almost any cost, was the mantra, everyone’s chief concern; conservation was a very low priority for business, government, and most citizens alike. One indication: Mexico did not join the Convention on International Trade in Endangered Species (CITES), the chief international agreement to stop trade in threatened and endangered plants and animals, in effect since 1975, until 1991, the last Latin American nation to do so. During the past few years, some big changes have taken place. Triggering growing environmental awareness in the country have been increasing education, local and international publicity over Mexico’s pollution levels and poor environmental record, the gradual weakening of the formerly omnipotent Institutional Revolutionary Party (PRI), and the emergence of a sizable middle class who vacation in the countryside and take vocal interests in living healthy lives. The dramatic decline in environmental quality has been noticed, and people and government have begun steps to reverse the decline.

Mexico has a host of environmental problems, including significant chemical pollution from factory discharges and waste dumping, but the main threat to its biodiversity probably stems from deforestation and other natural habitat losses. Forest habitat is lost for a number of reasons. The major factor is land use – land is cleared for crop agriculture, cattle grazing, human colonization, and for business development. A rapidly multiplying human population and economic growth propels and constantly increases these uses. (For instance, currently there is explosive population growth among the Yucatan Mayan people, owing to high birth rate, low infant mortality rate, and high immigration rate – mostly young people arriving to seek jobs in Cancun.) Other causes of forest loss are over-exploitation for timber and fuelwood, and natural agents such as fire and disease. The use of trees as fuel for heating and cooking takes an especially heavy toll on forests. In Oaxaca, for instance, it’s estimated that each family burns on average about 12 kg (26 lbs) of wood per day. Very few forested areas of Mexico are free from human disturbance; in fact, most forests contain scattered settlements whose residents are usually very poor and who still practice age-old slash-and-burn agriculture. The rate of forest loss, one of the highest in the world, is officially estimated at anywhere between 300,000 and 400,000 hectares (740,000 to one million acres) per year, but is actually higher – perhaps double these estimates. (Reforestation rates average less than 100,000 hectares, or 250,000 acres, per year.) Forests in some regions are destroyed faster than others, for instance, over half the forest cover in the Selva Lacandona region has been lost since 1980 (see below).

Compounding the ongoing threat to its forests and other natural habitats is the dawning realization that Mexico is a treasure trove of biodiversity and a center of endemic species – those that occur only in one place; destroy them in Mexico and they will be extinct. During the 1980s and early 1990s, as an initial, necessary step for conservation, Mexico underwent surveys and censuses of much of its biodiversity. The results are in, and they are stunning. Mexico, it turns out, probably holds more species of plants and animals than any other country on earth but two. For instance, there are some 30,000 plant species, of which between 50% and 60% are endemic; 49 species of pines (more than half the world’s total); 450 mammals (Brazil, which is more than twice Mexico’s size has only 394 mammals); about 1000 birds, 693 reptiles; 285 amphibians, and more than 2000 fish. As of the mid-1990s, many species were known to be already threatened: 64 mammals, 36 birds, 18 reptiles, 3 amphibians, and about 85 fish.

Wildlife surveys, in addition to identifying and counting species, note where they are located and in which habitat types they occur, so that biologists can target and prioritize geographic regions and habitats for conservation attention. That is, they can determine which habitat types are most threatened and where, and which ones, based on their biodiversity, are most worth trying to save. For instance, the last large expanse of virgin tropical forest in North America, Chiapas’ Selva Lacandona (the Lacandon Jungle), near Mexico’s border with Guatemala, with its high level of biodiversity, has now become a top conservation priority for Mexico and for international conservation organizations. Likewise, wetland areas along the Yucatan Peninsula’s coasts were recognized for their biodiversity holdings and identified as critical migratory bird stop-over habitat and as a result, recently were given given protection as biosphere reserves. Overall, based on its degree and rate of habitat loss and the amount of biodiversity it holds, Mexico is now considered one of the 15 most environmentally threatened places in the world.

As I said above, environmental concern is growing in Mexico and corrective actions increasing. International publicity about Mexico’s pollution problems has helped. Drawing most interest probably is the USA/Mexico border region, where for decades USA companies and others set up industrial and manufacturing plants on the Mexico side to take advantage of lax Mexican environmental regulations and cheap labor costs, while at the same time maintaining close access to USA markets. The practice took on special significance to international media when it was realized that dumping wastes into northern Mexican rivers and bays, for instance, polluted not just Mexico but adjacent regions of the USA as well. Recent trade deals among North American nations (NAFTA, etc.) have associated environmental provisions – side agreements – that obligate signatory nations to regulate relevant industry to reduce pollution. Grass-roots support in Mexico for conservation and against rampant development is also growing. A recent golf resort development within easy driving distance of Mexico City, for use of the city’s elite, which in the recent past would have been built easily and quickly, was held up because local townspeople did not want their wild countryside marred by development. This activism is a new way of doing things for Mexico and speaks well for its future conservation efforts. There is a new Green Party, but it garnered less than 1% of the vote in mid-1990s national elections.

In 1996, the new government of President Ernesto Zedillo consolidated several ecology and wildlife services to form a new Secretariat of the Environment, Natural Resources, and Fisheries (SEMARNAP) and staffed it with respected enviromentalists. Most observers believe this reorganization represents a sincere effort to begin addressing the nation’s need for strong environmental protection and conservation. However, as in most other nations of Latin America, even when public atmosphere and governmental good-will exist for conservation, necessary funds are usually lacking. In relatively poor countries (Mexico’s per capita gross domestic product in 1994 was US$ 7900), where there is always critical need for increased spending for roads, public health, and education, money for conservation is always hard to find. Parks and reserves can be established with the stroke of a pen, but often they are protected reserves in name only. There are no funds to hire the managers and wardens to patrol and protect the habitats and wildlife. Sometimes a single guard or caretaker is responsible for overseeing vast tracts of land, and can do little to prevent habitat destruction and wildlife poaching.

Mexico has been slow to realize that natural habitats attract capital, and that wild habitats have, to some degree, the capacity to help save themselves, through ecotourism. But efforts are underway now by international and local non-profit conservation organizations and by state and federal governments to use ecotourism to help preserve some of Mexico’s ecological treasures.

Conservation Programs and Ecotourism
Biosphere Reserves
Chief among Mexico’s conservation efforts must be its establishment of reserves to protect areas with threatened or fragile habitats and the plants and animals they contain. The country has long had several protected areas, but the pace of declaring reserves, especially larger ones with critical, high-biodiversity habitats, significantly quickened during the 1980s and 1990s, as the deteriorating nature of Mexico’s last wild areas became known. As of this writing, Mexico has more than 70 protected areas that, in total, make up about 3% of the national territory. Many of these protected lands are smaller parcels in the form of national parks (defined by Mexico as areas with special historical, scientific, ecological, or aesthetic value) and natural monuments (areas with unique natural beauty or scientific value), but most of the total area is included within large wild zones known internationally as biosphere reserves.

The first biosphere reserves were designated in 1976 and, as of 1997, there were 337 of them in 85 countries, covering 200 million hectares (500 million acres). Mexico now has about 10 biosphere reserves, defined by the United Nations scientific arm (UNESCO) as protected areas, generally larger than 10,000 hectares (24,700 acres), that contain one or more important biological zones and that include significant pristine, or wilderness, areas, untouched by people. Smaller protected areas (less than 10,000 hectares, or 24,700 acres) that meet most of the requirements of biosphere reserves, are known as special biosphere reserves, and Mexico also has more than 10 of these (for example, Ria Celestún and Ria Lagartos reserves). Mexico’s biosphere reserves are generally acknowledged to be its best-protected lands. The purpose of biosphere reserves, after 20 years of trial and error learning, has evolved to be three-fold: to conserve biological and cultural diversity; to develop and serve as models for sustainable land use; and to provide areas for environmental research, monitoring, training, education, and tourism.

Biosphere reserves are structured in a special way to facilitate these goals. They contain one or more core or nuclear zones, true wilderness areas designated for the strongest degree of long-term conservation protection; only research relevant to conservation and perhaps limited, low-impact tourism are allowed in these zones. Surrounding the core zones are buffer zones, meant to protect the core from human intrusion and in which limited activities relevant to conservation are permitted, such as education, research, ecotourism, non-destructive recreation, and low-impact uses of natural resouces. Surrounding or adjacent to buffer zones are transition zones, where local communities may live and, usually with training from conservation agencies, engage in sustainable uses of natural resources. (Sustainable means using plants and animals in ways that are economically profitable for the local economy yet not ecologically harmful; use, in other words, that will not lead to significant ecosystem damage or to decline in biodiversity.)

A good example of how one of these reserves works and how local and international conservation organizations play major roles, can be found in the Yucatan Peninsula’s Calakmul Biosphere Reserve. This large reserve on Mexico’s southern border is continuous with the Guatemala’s Maya Biosphere Reserve; it’s primary mission is to preserve the biodiversity contained within this largest patch of remaining tropical forest north of the Amazon region. At least 350 bird species occur here, as do about 100 mammals and more than 50 reptiles and amphibians. Calakmul, named for the ancient city of the same name whose ruins still exist in the southern part of the reserve, consists of two large core zones surrounded by buffer/transition zones made up of ejidos (lands held communally by local villages; see below) and their associated forest reserves.

The most important conservation organization working today in the Yucatan Peninsula and, in particular, to protect Calakmul and conserve its biodiversity, is Pronatura Yucatan, a Mexican group with headquarters in Merida. (Pronatura does the hands on work but receives financial and other assistance from organizations such as The Nature Conservancy, World Wildlife Fund, and the former US Agency for International Development.) About 15,000 people live in and around Calakmul and make their livings there, often by means that are environmentally harmful. The biggest problem is deforestation, primarily caused by traditional slash-and-burn farming and logging for timber. Protecting these critical forests lies not in simply establishing a reserve and then telling residents they can no longer use the natural resources they depend on. That kind of treatment, experience shows, leads only to local resentment and lack of compliance with conservation rules. Rather, most modern conservation organizations, such as Pronatura, believe that the way to protect remaining forests and biodiversity in core areas is to work with local people in surrounding zones so that they, too, have strong incentives to preserve wild habitats. In other words, if local residents can be taught to manage their forests in sustainable ways, it will be better in the long run for the local people – it will improve their lives – and also better for conservation.

So what, exactly, does Pronatura do in Calakmul? In a phrase, lots of things – some of which, at first, you might not imagine are strongly related to conservation of trees, birds, and bugs. But most are aimed at improving the lives of local residents who live in or near the reserve so that their dependence on harmful environmental practices is reduced. For instance, Pronatura conducts workshops in many villages in environmental education (composting, gardening, hog farming, etc.), reproductive health and family planning, and traditional medicine (with help from community experts); they train villagers for and help with rainwater catchment projects (lack of water during dry season is a major community problem) and infrastructure improvements (putting up signs, etc.). Their major emphasis, however, is on training local people in agro-ecology projects – teaching them to support themselves in environmentally-friendly ways. One of the main projects at Calakmul is teaching people to plant crops of legumes – plants such as beans that, as they grow, tend to put nutrients back into soils. These crops actually improve soils so that the same fields can be used year after year. Repeated use means that new fields do not have to be cleared every few years from the forest when soils become nutrient-poor (the traditional slash-and-burn method). Another major agro-ecology project pursued now in Calakmul is honey production. More than 120 individual producers in about 14 villages are keeping bee hives and harvesting honey, which is marketed as Jungle Honey. For the time and effort investment, honey production is quite profitable (after all, the insects making the stuff work for below minimum-wage). It has been quite successful of late, keeps people working all year (whereas much local employment is only seasonal) and, from a conservation perspective, is truly an eco-friendly industry. Pronatura helps in the training aspects of honey production (finding local experts to give workshops on bee-keeping and working with aggressive Africanized honeybees, helping to obtain materials, and getting people started), but not in the commercial aspects – local people market their own product.

In the end, it will probably be huge biosphere reserves in Mexico and other countries – where both core wilderness areas and large buffer zones enjoy high degrees of protection – that will offer many species their best chances of survival. As in any new discipline, the scientific field of conservation biology is rife with controversies, but there is general agreement that preserving large wild areas is probably the only way to save many species from rapid extinction. For instance, viable populations of larger mammals, such as howler and spider monkeys, white-lipped peccaries, and tapirs (Plates 73, 80) cannot possibly be successful in small patches of forest.
Aside from moving all people from the earth, no conservation method is likely to be perfect – they all have pluses and minuses. Ecotourism is no exception, and I mention some negatives at the end of the chapter. However, on balance, most conservationists agree that ecotourism can be used successfully to help preserve many wild habitats. Indeed, conservation organizations in southern Mexico are increasingly fostering ecotourism with the hope that visits to remote sites by tourists, and the economic surge they bring, can help preserve those sites. One of the Yucatan Peninsula’s early efforts at ecotourism, visits to the Sian Ka’an Biosphere Reserve, led by the Amigos de Sian Ka’an organization, is detailed elsewhere in the book. Ecotourism in the remote Calakmul Biosphere Reserve is beginning – the conservation agency Pronatura Yucatan, in fact, recently started training local guides. Pronatura, again with technical advice and financial assistance from orgazinations such as The Nature Conservancy, also has been instrumental in helping two communities on the peninsula’s coast establish ecotourism businesses. In both Rio Lagartos and Celestún, Pronatura worked with the local communities to establish boat tours for visitors to see flamingos and other wildlife inhabiting the biosphere reserves that surround these two towns. In addition to businesses relating to boat tours, the organization works with other sections of the communities to promote eco-friendly cottage industries. For instance, in the town of Celestún, a women’s group was organized that now runs a successful small business gathering ocean shells, making from them household objects such as napkin holders, and selling them in the town plaza. Ria Lagartos and Ria Celestún Special Biosphere Reserves protect important wetlands, habitat for many water-associated birds and other kinds of animals. In fact, owing to its critical function as bird nesting habitat and also wintering habitat and stopover habitat for many migratory birds, and to the high number of threatened species it contains, Ria Lagartos in 1986 was placed on the international “RAMSAR” list of essential wetlands (as Mexico’s only entry). The list is the result of the Convention on Wetlands of International Importance, signed in Ramsar, Iran in 1971; it prioritizes the world’s wetlands for conservation purposes.

So ecotourism on the Yucatan Peninsula started only recently and is growing slowly. Its biggest obstacle may be that local governments, especially in Quintana Roo and Yucatan states, are, so far, doing little in the way of promotion (Campeche is a bit more on the ball, and has even collaborated with Pronatura in training nature guides). Also, SEMARNAP, the federal agency now charged with protecting natural resources, is cautious about ecotourism, probably because they know that if it is not handled correctly, it can lead to over-visitation of sites and environmental damage.

Chiapas is perhaps a bit behind even the Yucatan Peninsula in ecotourism development because of the remoteness of some of it’s attractions and its recent political unrest. Nonetheless, Chiapas now has several fantastic eco-attractions and is beginning to promote them and render more of them reachable by ordinary people. The Chiapas state government appears to support ecotourism strongly, and conservation organizations are increasingly using ecotourism in the state to try to save wilderness areas. Conservation International (CI), for instance, is one agency heavily involved with trying preserve the Selva Lacandona (Lacandon jungle) ecosystem that lies in northeast Chiapas near the Guatemalan border. The region is irreplaceable from a biodiversity perspective. At about 1.8 million hectares (4.5 million acres), the Selva Lacandona contains about 30% of all animal and 20% of all plant species found in Mexico, and represents the last large remaining tract of North American tropical rainforest. But this wonderful wild region is under attack by an increasing human population and associated deforestation; it’s estimated that half the forest has been cleared since 1980. Looking at a satellite image of the area is sobering and slightly eerie: On the Guatemalan side of the Usumacinta River is the unbroken greenery of virgin tropical rainforest, a tribute to the remoteness of the region and lack of roads on the Guatemalan side of the border that prohibits access to settlers; on the Mexican side however, where the Selva Lacandona is situated, are huge patches of deforestation, the result of human penetration into the area after the Mexican government pushed roads into the region for their military to patrol the border.

On paper, some of the Selva Lacandona is now protected, with the Montes Azules Biosphere Reserve probably the best protected and most important part. But protection on paper is not sufficient. Local residents, most often poor and poorly-educated, must be convinced that wild areas are worth saving, and ecotourism development is one way to do that. CI and other organizations work with these local communities to help them create infrastructure for ecotourism. They hold workshops to train local people in potential ecotourism activities such as offering guide services, lodging, and transportation, and, fundamentally, describing what tourists want from the experience of visiting the area. The most successful outcome to date of these training activities are the wonderful tours that now depart daily from Palenque for the remote Mayan ruin sites of Bonampak and Yaxchilan. CI helped set up the organization for these tours, but local people from the indigenous communities located around the archaeological sites now run and profit from the tours. The success of the operation is evident: other indigenous communities have begun asking how they, too, might participate in ecotourism, and CI has been working to expand their success to other, even more remote regions of the Selva Lacandona (for example, in the Laguna Miramar region).
Ejidos, Conservation, and Ecotourism
One of the few acknowledged truths of ecotourism is that, if local people and communities of modest means are to accept and support conservation measures and new nature reserves, they should be informed and consulted during all phases of the development process. For their continued support, local people should benefit economically from a park, reserve, or ecotourism facility, but local communities should also have a hand in the decision-making concerning the development and maintenance of ecotourism sites. In southern Mexico, complicating the ecotourism and conservation picture is the fact that impoverished local people own or occupy most of the land. These people can be divided into four main groups, and conservation agencies must sometimes work with all of them to achieve conservation success: A community is a large group of indigenous people that hold, as a group, huge chunks of tribal lands. The Lacandon Community, for instance, with which Conservation International worked to establish tours to the Bonampak and Yaxchilan Mayan sites, is composed of the Lacandones, Choles, and Tzeltales peoples. An ejido (eh-HEE-doe) is a smaller group, usually about 400 to 600 people, which owns a smaller parcel of communal land, often, in total, about 50 hectares (125 acres) per person, but sometimes much less. About 70% of Mexico’s remaining forests are now owned by communities and ejidos. A third kind of people who often must figure prominently in conservation strategies are new immigrants – the many people who, for example, recently fled into the Selva Lacandona region of Chiapas to escape the political unrest in other parts of the state. New immigrants immediately begin cutting trees for houses and fuelwood, and need jobs, and therefore, can have strong impacts on forests. The fourth category of local people important for conservation are private landowners. Land containing perhaps 20% of Mexico’s remaining forests is held by small landowners and, in larger pieces, by the remnants of the hacienda system – the large pieces of Mexican real estate handed out by the Spanish crown during colonial times as rewards for services rendered. The attitudes of these different groups toward conservation depends on their use of forest resources. The Lacandon people, for instance, actually live in the jungle – it is their home – so they quickly understand the need for conservation. They see the logging and burning of forests as threats to their very way of life. But other groups, not so intimately tied to the forests, are not clear on the need for conservation. Some ejidos, for example, may understand that there is some money to made through ecotourism, but really don’t understand or care about the conservation implications of such activities. Conservation agencies work with these communities to educate them about the need for conservation and the relationship between ecotourism and conservation.

Ejidos themselves are increasingly offering ecotourism services. Inequitable land ownership was a main cause of the Mexican Revolution early in the 20th century; 90% or more of rural families at the time owned no land. Land redistribution was enshrined in the post-revolution 1917 Constitution. Land was confiscated mainly from the colonial haciendas and by 1981, nearly 100 million hectares (2.5 million acres) had been distributed to more than 1.5 million people. (Unfortunately, much of this land was of poor quality for agriculture.) As a way to prevent lands from ever again becoming concentrated in the hands of a few wealthy individuals, the ejido system was created. Each person was given land to work in a collective agricultural unit. In addition, each ejido (made up of several hundred people) was provided with large tracts of common land for use of all people in the ejido for grazing livestock and for collecting forest products – fuelwood, timber. (It is these associated forests lands held by ejidos that are often important for conservation purposes). All ejido lands are owned by the Mexican nation in perpetuity; they cannot be sold, and must be returned if not worked. The ejido, however, is a self-governing land unit, a cooperative with elected officials; it decides how best to use its lands and what to do with profits from ejido agriculture and commerce (V. Halhead 1984). And some ejidos, at the urging of conservation organizations, are turning to ecotourism as a new, eco-friendly way to generate income.

Some of these ejidos are already operating rustic ecotourism lodges, and others are in the planning stages. The ejido Tres Garantias in southern Quintana Roo (located about 30 km, or 18 miles, south of Route 186, the main road that cuts across the base of the Yucatan Peninsula) has set aside half its forested lands as a nature reserve, built an enclosed camping hut with mosquito netting in the middle of the jungle, and opened its doors to ecotravellers. For very reasonable rates you can sleep there, get fed, and wander the lands and trails. Conservation International has been working with the ejido Emiliano Zapata in the Laguna Miramar region of the Selva Lacandona to initiate ecotourism. Laguna Miramar is a large lake in a wilderness area in eastern Chiapas. Visitors camp in a communal hut and spend their days exploring the lake, nature trails, and nearby archaeological ruins. Eventually, Conservation International would like to extend this kind of ejido-based ecotourism to the other sites in the Selva Lacandona, such as the Laguna Ocotal area in the northern reaches of the Montes Azules Biosphere Reserve. Another good example of ejidos participating in ecotourism is the cloud forest trips to the El Triunfo Biosphere Reserve (p. x) in southeastern Chiapas. Mexico’s Institute of Natural History worked closely with local ejidos (about 25 ejidos are located within the reserve’s buffer zones) to establish the tours, and members of ejidos work as guides, cooks, etc. Similarly, the Institute of Natural History hopes to work with ejidos near the new La Encrucijada Biosphere (or Ecological) Reserve on the Pacific in southeastern Chiapas to open that site also to ecotourists.

Ecotourism is a kind of sustainable development and can certainly contribute to conservation. But does ecotourism always help local economies and significantly preserve visited habitats and wildlife? This question is important because increasingly, the fostering of ecotourism is suggested by indigenous people in developing nations, by the nations themselves, and by international conservation organizations, as one of the best methods to preserve natural resources and biodiversity almost anywhere that they are threatened. Many people who monitor tourism – researchers and government officials – believe that in the rush to make money from ecotourism, benefits are often overstated and problems ignored.

Many private companies purporting to be “ecotour” operators are “eco-” in name only; they are interested solely in profits, and are not concerned about local economies or the wild areas into which they take tourists. There is increasing concern about monetary “leakage”: despite attempts to keep most of the ecotourist revenues in local destination economies, many of those dollars, more than 50% by recent estimates, leak back to large urban areas of destination countries and even to developed nations; relatively little actually is spent on conservation. (In southern Mexico, ecotravellers can visit ejidos or take tours operated by indigenous groups, thereby assuring that 100% of the fees charged go to local people.) In some countries, ecotourism is an unstable source of local employment and economic well-being. Tour bookings are heavily dependent on seasonal trends, on the weather, on a country’s political situation, and on worldwide currency fluctuations. Finally, popularity as an ecotourism site may inevitably lead to its failing. As ecotourism expands dramatically, sites that are over-used and under-managed are damaged. Trails in forests gradually enlarge and deepen, erosion occurs, crowds of people are incompatible with natural animal behavior. A good example: the number of visitors to Ria Lagartos Biosphere Reserve on the northern coast of the Yucantan Peninsula has been declining, probably because the flamingos that are the primary attraction are increasingly moving to other areas to escape tour boat harassment. Also, ecotourism’s success harms itself in another way: when any area becomes too popular, many travellers wanting to experience truly wild areas and quiet solitude no longer want to go there; that is, with increasing popularity, there is an inexorable deterioration of the experience.

Thus, ecotourism is not a miracle cure-all for conservation; these days it is understood to be a double-edged sword. Clearly, large numbers of people visiting sites cannot help but have adverse impacts on those sites. But as long as operators of the facilities are aware of negative impacts, careful management practices can reduce damage. Leakage of ecotourist revenue away from the habitats the money was meant to conserve is difficult to control, but some proportion of the money does go for what it is intended and, with increased awareness of the problem, perhaps that proportion can be made to grow. Travellers themselves can take steps to ensure that their trips help rather than hurt visited sites.

This is an excerpt from the author’s Tropical Mexico: The Ecotravellers’ Wildlife Guide, (Academic Press, 1998).

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