Mammal Neotropics Populations

TITLE: THE FACTORS AFFECTING MAMMAL POPULATION IN THE NEOTROPICS AND THE CHALLENGES TO MANAGE THESE POPULATIONS.

Mammals belong to the phylum Chordata. Chordates have an internal flexible rod, the first stage in the evolution of a truly internal endoskeleton. Muscles attached to this rod allowed early chordates to swing their backs from side to side, swimming through water. This key evolutionary advance, attaching muscles to an internal element, started chordates along an evolutionary path that led to the vertebrates. Vertebrates have a true, usually bony endoskeleton, with a backbone encasing the spinal column, and a skull-encased brain.

Mammals are distinguished from all other classes of vertebrates by two fundamental characteristics that all mammals possess and no other living vertebrates do: all mammals have hair, even apparently naked whales and dolphins grow sensitive bristles on their snouts and all female mammals possess mammary glands that secrete milk.

The 1996 Red List, published by the Species Survival Commission of the World Conservation Union in Gland, Switzerland, contains 5205 species assessments conducted by more than 500 scientists worldwide. Published since the early 1960s, the list for the first time evaluates the status of the estimated 4600 known mammal species. According to the report, 24 of the 26 orders of mammals include species facing extinction, for a grand total of 1096 species. A leading cause of population decline, according to the report, is habitat degradation—due mostly to human population growth and economic development. The introduction of nonnative species also factored as a significant threat to species' survival, along with over hunting, pollution, and climate change.

Mammals have the smallest number of species in any of the five classes of vertebrates. Almost all large, land dwelling vertebrates are mammals, and they tend to dominate terrestrial communities, as did the dinosaurs they replaced. Of the 4600 species of mammals identified, approximately 3200 are rodents, bats, shrews or moles. There are 19 orders of mammals, 17 of them (containing 94% of all species) are placental. The other two are the primitive monotremes and the marsupials.

These animals are endothermic, and typically maintain body temperatures higher than the temperature of their surroundings. The dense undercoat of many mammals reduces the amount of body heat that escapes. Mammals possess a four-chambered heart and a closed circulatory system.

THE NEOTROPICS

The Neotropical Region is one of the six major biogeographic regions of the earth, extending from South of the Mexican desert to South America as far into the Subantartic Zone. This is the most biologically diverse region to be found. The climate is variable. It ranges from the hot dry Atacama Desert of Chile and the vast grasslands of Argentina through the humid tropical rainforests of the Amazon Basin to the cold grasslands and barren rocky landscapes at the highest elevations.

The habitats found in this region have been mostly named and includes: The Cattinga, which includes areas of dry shrub lands in northeast Brazil, extend over 800,000 square kilometers. They have virtually no grass substrate and more dry season moisture availability. Do not qualify as cerrado as it has virtually no grass substrate. The Cerrado is the Brazilian savannahs where there is a wide density of trees over the savannas, especially in the well-drained savannas; these range from pure grasslands to virtual forests. In Brazil, savannas are referred to as: campo limpo (clean grass fields), campo sujo (grassland with some shrubs), and cerradão (closed savanna approaching a forest). Llanos includes seasonally inundated grasslands and wetlands in Venezuela, Colombia, and Bolivia. Pampas are temperate grasslands in Argentina, Uruguay, and Paraguay covering some 777,000 square kilometers. Patagonia are semi-arid, temperate grasslands. Regional Savannas and Wetlands includes small patches of savanna woodlands within the Amazon basin provide "stepping stones" between the Pantanal and the llanos, etc.

THE FACTORS AFFECTING MAMMALIAN POPULATIONS IN THE NEOTROPICS AND THE CHALLENGES TO MANAGE THESE POPULATIONS

Humans have the greatest disruptive impacts of all. All over the world, humans are reducing extensive forests to isolated patches by clear-cut logging and land clearance for farming and development. Although this is general for all animals, mammals are becoming endangered and extinct because of the mere fact that their habitats are being destroyed. There is no place like home. Pollution, drainage of wetlands, conversion of shrub lands to grazing lands, cutting and clearing of forests, urbanization and suburbanization, and road and dam construction have destroyed or seriously damaged and fragmented available habitats.

Deforestation- when tropical forests are cleared, the ecological consequences can be disastrous. Tropical rainforests are biologically the richest of the world's biomes. Most other kinds of tropical forest, such as seasonally dry forests and savannah forests, have already been destroyed-because they tend to grow on more fertile soils, they were exploited by humans a long time ago. Now the rainforests, which grow on poor soils, are being destroyed. In the mid-1990s, it is estimated that only about 5.5 million square kilometers of tropical rainforest still exist in a relatively undisturbed form. About 160,000 square kilometers are being clear-cut every year, with perhaps an equivalent amount severely disturbed by shifting cultivation, firewood gathering, and the clearing of land for cattle ranching. At this rate, all of the tropical rainforest in the world will be gone in about 30 years; but in many regions, the rate of destruction is much more rapid. Large-scale forest fires, timber extraction by local and foreign companies, mining, the building of dams, and population growth have also made significant contributions to forest loss in the Neotropics over the past decade. Population growth and economic expansion have led to the construction of new roads and buildings that both physically and ecologically fragment the forest, reducing its vitality. It is expected that the populations of most Neotropical countries will double within the next 25 years, only increasing the already growing pressures on the forests.

Pollution- many forms of pollution arise as by-products of industry. Chemical pollution is causing ecosystems to accumulate many harmful substances, as the result of spills and runoff from agricultural or urban use. Industrial pollutants such as nitric and sulfuric acids, introduced into the upper atmosphere by factory smokestacks, are spread over wide areas by the prevailing winds and fall to earth with precipitation called “acid rain,” lowering the pH of water on the ground and killing life. Researchers theorize that another possible cause is increased exposure to ultraviolet radiation from the Sun as a result of the thinning of the atmosphere's ozone layer; the increased dose of ultraviolet radiation.

Exploitation- mammals have been exploited for centuries for food and other products such as fur for coats, etc. causing various species to become endangered and even extinct.

Habitat Fragmentation-Habitat fragmentation, the isolation and division of habitats into smaller areas, has caused plant and animal species in the remaining islands of habitat to lose contact with other populations of their own kind. This reduces their genetic diversity and makes them less adaptable to environmental or climatic change. These small populations are highly vulnerable to extinction. For some species, the fragmented habitats become too small to support a sustainable population.

RainforestConservation-Since the 1970s, an increasing number of national and international organizations have been established to promote rain forest conservation. In recent years, two principal approaches have been used to conserve tropical rain forests: strict protection and sustainable development. The first, outright protection through the development of national parks and preserves has been an essential element in biodiversity conservation. In this method of conservation, entire tracts of the rain forest are set aside, and uses are carefully regulated. Protected areas are especially important for preserving the most biologically distinctive rain forests—that is, those forests with exceptionally high species diversity with many species endemic to that forest. Over the last 20 years, the number of national parks in tropical countries has increased significantly, and today approximately 5 percent of all forests are classified under some protected status. International organizations such as the World Bank and the World Wildlife Fund have launched a movement at the end of the 20th century for all countries in the developing world to set aside 10 percent of their forests in protected areas.

Yet protecting these designated areas is costly and even impossible in some areas. Communities living near the rain forests may rely on the rain forest for food and firewood. When restricted from using rain forest land, these communities find it more difficult to meet their subsistence needs. To lessen these adverse effects, community-based programs have been developed that provide sustainable economic alternatives to destructive harvesting and land use.

One alternative for some forests is sustainable rain forest logging, in which the trees logged are carefully selected to ensure a minimal impact on the forest ecosystem.

FORMATION OF INTERNATIONAL SAFEGUARDS

IUCN

In 1976 the World Conservation Union (IUCN), an international conservation group comprised of government and nongovernment organizations, established Trade Records Analysis of Flora and Fauna in Commerce (TRAFFIC) to monitor and report on worldwide trade in wild animals and plants. Although CITES provides the framework for international cooperation to stem illegal trade in endangered species, TRAFFIC monitors both legal and illegal trade. TRAFFIC is intended to provide an early warning system for excessive trade. Its data can be used to bring sanctions against nations that fail to comply with CITES.

Implanted microchips are also increasingly being used by veterinarians for identification of individual endangered animals. Thus far, this technology has primarily been used to help manage captive breeding programs. But many experts believe microchips offer the potential to permanently and inconspicuously mark wild animals as well, allowing authorities to detect wild animals and return them to their native habitats.

CITES

CITES is the worldwide “law” that protects endangered species and limits the illicit trade in wildlife among nations. Drawn up by the United Nations (UN) in 1973, this treaty came into force in 1975 when the United States and 17 other nations became parties to it. As of January 1, 1998, 143 of the world's nations had become parties to the treaty.

CITES lists endangered plant and animal species in three “Appendices.” Appendix I include those species threatened with extinction that may be affected by illicit trade. Appendix II includes species that are not necessarily yet in danger of extinction, but could easily become so unless trade is strictly regulated. Appendix III lists any species that individual nations want to have protected. Species similar to endangered plants or animals are also included in these appendices to help distinguish them from their troubled relatives and to protect them from exploitation. About 2500 animal species and 30,000 plant species are currently listed in the three appendices.

Although CITES is intended to protect endangered species threatened with excessive commercial exploitation, many observers believe the treaty is ineffective and possibly even counterproductive. First, critics note problems associated with the listing of endangered species in separate appendices. For example, the inclusion of a species in Appendix I can drive up black-market prices for that species, encouraging more poaching and stockpiling of commodities, including rhinoceros horn, elephant ivory, and tiger bone.

In addition, listing a species in Appendix I for some populations and in Appendix II for other populations can encourage “laundering” of individuals from the endangered population by labeling them as from the less-threatened population. This phenomenon is especially relevant to the trade in animal parts, due to the difficulty of distinguishing parts of an endangered species from parts of a non-endangered species.

CITES has no enforcement authority; enforcement of the treaty depends on passage and enforcement of laws by each signatory. Authorities of exporting nations are charged with enforcing their export laws relative to each species, while importing nations must enforce their importation laws. However, laws among nations vary greatly, and even when strong laws exist, many national authorities lack the resources, political will, or both to enforce them.

Lack of enforcement authority is highlighted by the inability of CITES to stem the considerable trade in endangered species that goes on within nations. In some nations, law enforcement authorities have even been found protecting illegal trade, rather than stopping it.

REFERENCES

Microsoft ® Encarta ® 2007. 1993-2006 Microsoft Corporation.

The Geography of Mammals: No. III. The Neotropical Region W. L. Sclater The Geographical Journal, Vol. 5, No. 5 (May, 1895), pp. 471-487

http://www.biodiversityhotsopts.org/xp/hotspots/neotropics.htm date accessed 2008-03-06

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