Wednesday, April 29, 2020
South America Essay Example
South America Essay Although industrialization is synonymous with progress, in the modern world it has also been the cause of many changes of energy and natural resources pattern of human settlement, social and economic context of health and in the natural environmental constituents. There have been so many instances in South America where lives have been lost, health damaged and serious injuries inflicted because environmental hazards have been ignored or the identification of hazards has taken too long. By understanding and identifying the risks early and establishing ways of assessing and controlling existing and new environmental hazards benefits associated with modernization may be enjoyed without degradation of environmental conditions.These days South America is facing various environmental problems. Among several causes of environmental pollution three major causes effecting the environment of South America are1.              Air pollution2.              Water pollution3.              Misuse of fertilizers insecticides.(Lamb, 2006, 145, 1)Air pollutionAir pollution is a serious problem which South America has faced for years. Due to air pollution percentage of oxygen in atmosphere is reducing day by day. As a result increasing number of people is suffering from lung problems. Poisonous gases in atmosphere are killing small animals bird sand effecting human lives. The precipitation areas in industries have caustic vapors these cause skin problems. In some industries people work in fluoride environment .Continuous exposure to fluoride leads to a disease Fluoric in which bones and teeth are effected. Air pollution is also casting drastic effect in vegetation of South America. The result of which is comparatively less and irregular rainfall, which again causes dryness and scarcity of water. These causes soil erosion because of which fertility of la nd reduces resulting in more loss of vegetation. The industrial areas of South America like Brazil, Argentina, and Uruguay severely suffer from air and water pollution.South American countries have vast deposits of mineral resources. Argentina abounds in deposit of coal, lead, copper etc, Columbia is a leading supplier of emerald, and Venezuela leads in production and export of oil outside Middle East, Venezuela ranks 8th in the world in production of diamonds. Mining is one of the major occupations in countries of South America. Major environmental impacts of mining operations are: (i) degradation of land; (ii) pollution of surface and ground water resources; (iii) pollution of air. (iv) Deforestation including loss of flora and fauna; (v) rehabilitation of effected population including tribal; (vi) impacts in historical monuments and religious places.Prime causes of Air pollution are follows1.              Poisons bases lice Sulfure d ioxyde, Nitrogà ¨ne oxydes, volatile hydro-carbons, etc.2.              Carbon monoxides and other Poisonous gases emitting from factories3.               Carbon dioxide emitting from factories when raw materials or fuel is burned increases global warming.4.              The Ozone layer in our atmosphere is constantly being effected by cfcs and aerosols emitted by electronic goods like refrigerators, air conditioners and Foam blowing factories.5.              Methane gas emitting from open garbage also contribute in increasing global worming. (Lamb, 2006, 199, 1-6)Water pollutionDue to water pollution lives of aquatic plants and animals are very adversely affected. Deaths due to water born diseases are increasing day by day in South America.Poisonous sewage wastes, plastic packets thrown in water bodie s are killing aquatic plants and animals.There are various causes of water pollution such as wastes running from industries and factories, septic tanks, oil secretion from water vehicles, wastes from construction sites etc thrown in water bodies. The rivers on South America like Amazon , Parana , Uruguay , Salvado flowing in industrial areas of Argentina , Brazil gets highly polluted with poisonous wastes thrown from industries. Poisonous pesticides used in agricultural areas get dissolved in ground water and effects human and animal health hazardously. Mineral extracted interact with ground and surface water thus polluting water resources. Loss of top soil due to deforestation also depletes ground water resources and results in drying up of perennial sources like springs and streams especially in hill areas. (Lamb, 2006, 121, 1)Environmental pollution due to misuse of fertilizers and pesticidesIn South America due to urbanization  availability of agricultural lan ds has decreased. To cope up with this problem increasing yield substantially was necessary. To fulfill this purpose use of fertilizers and pesticides are increasing day by day. Pesticides can be divided into three subgroups namely Insecticides, Fungicides Herbicides. Insecticides comprise of Chlorine, Phosphorous, Carbonate chemicals such as DDT, Aldrin etc. Herbicides are generally used for controlling growth of weeds. These cause less harm to the environment than insecticides. Example of Herbicides is Atrazine, Propachlor etc. Herbicides do not leave long term effect on soil. Fungicides are mostly used in vegetable farms and orchards. The factors such as soil type, depth of water table, rain fall infiltration and persistence of compound in soil determine the entry of any pesticide in ground water. Some water soluble pesticides get dissolved in ground water and enter into food and effect human and animal health. Some pesticides contain aromatic compounds which do not get degraded easily after washing fruits and vegetables. These pesticides along with food cause health hazards. Water soluble pesticides cause cancer, birth defects and gene mutation. Most of the agricultural areas of South America lie in Brazil. Brazil, the largest country of South America having 8,511,965 sq km area is mainly an agricultural country. Agriculture accounts for about 9% of GDP. In some areas of Brazil on the banks of Amazon River still primitive methods of agriculture are followed. Use of fertilizers and pesticides are limited in these areas. But in coastal areas of Brazil and Argentina, on banks of rivers Parana , Uruguay and Salvado modern techniques of agriculture are followed. Here fertilizers and insecticides are used extensively. (Lamb, 2006, 201, 2-7)Suitable remedies to control environmental pollutionThere are several ways to reduce environmental pollution.Plantation of trees reduces air pollution. Trees absorb Carbon Dioxide  and give out oxygen. This mai ntains atmospheric equilibrium.Industrial pollution can be reduced by following steps.Applying cleaner production means systematically addressing all phases of the production process and product life-cycle. Cleaner production encompasses energy and raw material conservation, reduction in the use of toxic substances and product and process changes that reduce wastes and pollutants previously produced. All these options have the same aim, to reduce the risk of human and the environment from industrial Activities and consumption, and to do so in the most cost effective way possible. Only the control methods, end-of-pipe (EOP) devises were devised to solve the problems of polluted surface waters , intoxicated air and other results of industrial developments. EOP wastes, also less hazardous than the raw wastes .Reducing domestic wastes in another way to prevent environmental pollution. Waste management includes taking measures so that garbage are not left open, recycling of waste product s which serves both the purposes of saving resources and reducing environmental pollution. Such as recycling plastic bags, bottles etc. , preparing paper and fertilizers from garbage. The process of making fertilizers from house hold wastes is called composting. The fertilizers in this process more useful in increasing soil fertility. Help of non profit organizations could be taken for this purpose. Technical know how could be taken from other countries in designing machines to solve this purpose.To reduce water pollution Llma dung can be used . This process is used in tin and silver mines of Bolivia to treat leaking poisonous waters. In this process polluted water is passed through compost beds of limestone and dung. BActeria living in this dung absorb acids in polluter water making it alkaline. It was invented by Professor Paul Younger, professor of Hydro chemical Engineering at Newcastle University. U.K. Lima dung is available in abundant quantities in South America, anim al husbandry being one of chief professions there.Another way of reducing water pollution is harvesting fish and oysters. These absorb metal content in water. Aquatic plants also serve this purpose. (King, 2006, 119, 4)Measures taken by Government of India to solve environmental problemsTo reduce environmental pollution according to the Forth Five year plan a committee set up in January 1980, for reviewing the existing legislative measures and administrative machinery for ensuring environmental protection and for recommending ways to strengthen them. In 1985 Ministry Of Environment And Forest was formed to serve as the focal point in the administrative structure for the planning , promotion and coordination of environmental and forestry programmes. Many enactments related to protection of environment now being administered by central and state governments. Such as The Water ( prevention and control of pollution ) Act,1974; The Air ( prevention and control of pollution ) Act,1981 ; The Water ( prevention and control of pollution ) Act,1977; The Environment Protection Act ,1986; etc. (Kar, 2006, 211, 3)The Environment Protection Act, 1986, provides for the protection of environment. The salient features of this Act are as follows: (a) conferring powers on the central government to :(i) take all necessary measures for protecting quality of environment ; (ii) coordinate Activities of states , officers , other authorities under this Act. (iii) Plan and execute a nation wide programme for prevention, control and abatement of environmental pollution; (iv) lay down standards of discharge of environmental pollutants. (v) Issue directions to any person, officer or authority including the power to direct closure , prohibition or regulation of supply of electricity water or any other services. Etc. (b) it offers powers to persons to complain to the courts regarding any violation of the provisions of the Act. (c) The Act makes obligatory for the person i n charge of a place to inform prescribed authorities regarding any accidental discharge or apprehended discharge of any pollutant in excess of prescribed standards. Authorities on receipt of such information shall take remedial measures to prevent mitigate pollution caused by such accidents and expenses incurred by the authorities in respect of remedial measures are recoverable with interest from the polluter; (d) it prescribed stringent penalties for violation of the provisions of the Act. (e) Jurisdictions of civil courts is barred under the Act. (King, 2006, 116, 3)The Ministry Of Environment and Forest has announced a policy statement for abatement of pollution in 1992, according to which ,the key elements of pollution prevention are adoption of best available clean and practicable technologies rather than end of pipe treatment. An environment Action Programme has been formulated covering wide ambit of subjects such as clean technologies, improvement of water quality , institutional and human resource development , forestry and natural resource accounting. An Eco-Mark label has been introduced to label consumer products that are environment friendly .Under the E(P) Act ,1986, affluent and emission standards in respect to 55 specific industries have been notified. 84 laboratories have been  recognized as environmental laboratories. Minimum National Standards (MINAS) for effluent emissions from specific industries have been formulated.Action plans have been formulated to divert the sewage flow into the river to other locations for treatment and conversion into a valuable energy source. Renovation of existing trunk rivers and outfalls to prevent overflow of sewage into rivers thus construction of interceptions to divert the flow of sewage and other liquid wastes in the river and renovations and construction of pumping stations and sewage treatment plants to recover maximum possible resources, construction of community toilets etc.Au tomobiles which have been used for 15 years have been banned.Methods of pollution control succeeded in India up to some extent. But major factors that hindered its success are1.              Lack of resources.2.              Lack of education3.              Orthodox mentality of people.4.              Corruption (King, 2006, 98, 1-3)ConclusionThe world today is under the grip of many pressing problems. Of them the problem of environmental pollution has reached a serious proportion; and it has undoubtedly posed a definite threat to man’s existence itself. All the governments of all the countries of the world have, every now and then been, giving expressions to their deep-toned worries and concern for it, the government of South America is one among them. The ecologists have been tirelessly working to explore the events and to device the means to combat and contain effectively this menace of environmental pollution. The pollution of environment owes its roots, to a very large extent, to the thoughtless and irresponsible acts of man. Environmental pollution may greatly be contained if the people can properly be educated in civic since. (Kar, 2006, 245, 3) South America Essay Example South America Essay Introduction The continent of South America has about one-eighth of the Earths land surface, situated between latitudes 12 °N-55 °S and longitudes 80 °-35 °W; no other continent has a greater latitudinal span. Eighty percent of its land mass is within the tropical zone, yet it extends into the subantarctic. The extensive zones of temperate and cold climates in the vicinity of the Equator, in the Andes, are unique. The land area of about 17,519,900-17,529,250 km? is under the jurisdiction of 13 countries (Table 49); French Guiana is governed as an overseas department of France. The regions 1995 population of c. 320 million people is estimated to reach 452 million people in 2025. Three of the worlds 21 megacities are in South America: Sao Paulo, Buenos Aires and Rio de Janeiro (WRI, UNEP and UNDP 1994). Geological setting Although the neotropics may be conveniently considered as a single phytogeographic unit, the region is geologically complex. The neotropics include not only the South American continental plate but the southern portion of the North American plate, as well as the independent Caribbean plate (Clapperton 1993). The complicated geological history of the region, for example as these plates intermittently separated and collided through the Cretaceous and the Tertiary, provides the milieu within which plant evolution has been superimposed. South America has been an island continent during most of the period of angiosperm evolution, whereas Central America constitutes one of the two tropical parts of the Laurasian world continent. Both South America and North America have been moving westward, roughly in tandem, since the breakup of Pangaea in the Mesozoic. We will write a custom essay sample on South America specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on South America specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on South America specifically for you FOR ONLY $16.38 $13.9/page Hire Writer In contrast, the Antillean plate with its flotsam of Antillean islands formed only during the Cenozoic and has moved in a retrograde eastern direction, at least with respect to its larger neighbours. Whereas South America and North America have been widely separated through most of their geological histories, there has been generally increasing contact between them through most of the Cenozoic, culminating in their coalescence with formation of the Isthmus of Panama c. 3. 1 million years ago (Keigwin 1978). The date of this epochal event in neotropical geological history has been gradually estimated to be younger, with estimates of 5. 7 million years ago giving way to as recently as 1. 8 million years ago (Keller, Zenker and Stone 1989). In addition to their Pleistocene connection via the Isthmus of Panama, South America and North America apparently were more or less directly interconnected via the protoAntilles for a short time near the end of the Cretaceous, prior to formation of the Caribbean plate (Buskirk 1992). The outstanding geological feature of South America is the Andes, the longest mountain range in the world, which extends in a nearly straight line of over 7000 km from the north to the southern tip of the continent. The Andes have the highest mountain in the Western Hemisphere, the highest mountain in the worlds tropics, and as measured from the centre of the Earth (rather than metres above sea-level), the highest mountain in the world. The most important break in the north-south sweep of the cordillera is the Huancabamba Depression in northern Peru, where the eastern chain of the cordillera is entirely ruptured (by the Maranon River) and even the western chain dips to 2145 m (at the Abra de Porculla). The existence of this massive mountain range has had profound effects on plant and animal evolution in South America, and consequently has profound effects on essential conservation priorities. In essence, the Andes represent a classical plate tectonic upthrust of continental rock, as the leading edge of the westward-moving South American plate collides with the oceanic Pacific plates. The Southern Andes are the oldest, with significant uplift already present in early Cenozoic times, prior to the Oligocene. Most of the uplift of the Central Andes was in the Miocene or later, whereas most of the uplift of the northern portion of the cordillera has been Plio-Pleistocene (van der Hammen 1974). To the north the Andes become more geologically complex, breaking into three separate cordilleras on the Ecuador/Colombia border. Much of the north-western margin of South America, including Colombias western and central cordilleras, appears to be amassed suspect terrane rather than an integral part of the South American continental plate (Juteau et al. 1977; McCourt, Aspden and Brook 1984). Much of the rest of the South American continent consists of two great crystalline shields that represent the western portion of what was once Gondwanaland. The north-eastern portion of the continent constitutes the Guayana Shield, whereas much of Brazil south of Amazonia is underlain by the Brazilian Shield. These two major shields were formerly interconnected across what is today the Lower Amazon. They consist of a Precambrian igneous basement overlain by ancient mucheroded Precambrian sediments. The Guayana region has been the most heavily eroded, with basement elevations mostly below 500 m interrupted by massive flattopped table mountains, the fabled tepuis, typically rising to 2000 m or 2500 m. The peak of the highest of these, Cerro Neblina or Pico da Neblina on the Venezuela/Brazil border, reaches an altitude of 3015 m and is the highest point in South America outside the Andes. The tepuis and similar formations are highest and most extensive in southern Venezuela, becoming smaller and more isolated to the west and east where La Macarena near the base of the Andes in Colombia and the Inini-Camopi Range in French Guiana respectively represent their ultimate vestiges. The quartzite and sandstone of the Guayana Shield erode into nutrient-poor sands, and much of the Guayana region is characterized by extreme impoverishment of soils. The rivers draining this region are largely very acidic blackwater rivers, of which the Rio Negro is the most famous. The Brazilian Shield is generally higher and less dissected, with much of central Brazil having an elevation of 800-1000 m. The Brazilian Shield is mostly drained by clearwater rivers such as the Tapajos and Xingu. In contrast to these ancient shields, the Amazonian heartland of South America is low and geologically young. Prior to the Miocene most of Amazonia constituted a large inland sea opening to the Pacific. With uplift of the Central Andes, this sea became a giant lake that gradually filled with Andean sediments. When the Amazon River broke through the narrow connection between the Guayanan and Brazilian shields near Santarem, Brazil, Amazonia began to drain eastward into the Atlantic. Nevertheless, the region remains so flat that ocean-going ships can reach Iquitos, Peru, which is only 110 m above sea-level, yet 3000 km from the mouth of the Amazon and less than 800 km from the Pacific Ocean. Most of Amazonian Ecuador, Peru and Bolivia is below 200 m in elevation. The process of Amazonian sedimentation is continuing, as the sediment-laden white-water rivers course down from the Andes, continually changing their channels and depositing and redepositing their sediments along the way. About 26% of Peruvian Amazonia shows direct evidence of recent riverine reworking (Salo et al. 1986). With the lack of relief, it is not surprising that rather fine nuances of drainage, topography and depositional history are often major determinants of vegetation. Like Amazonia, some other distinctive geological features of the South American continent are relatively low, flat and geologically young, such as the chaco/pantanal/pampa region to the south, the Venezuelan/Colombian Llanos to the north and the trans-Andean Choco region of Colombia and Ecuador to the west. Large portions of these areas have been inundated during periods of high sea-level in the past, and large portions of all of these regions are seasonally inundated presently. One aspect of the geological history of Latin America that has received much biogeographic attention is the series of Pleistocene climatic fluctuations and their effects on distribution and evolution of the present neotropical biota. It is clear from the palynological record that major changes in vegetation were associated with the cycles of Pleistocene glaciation (e. . van der Hammen 1974), although to what extent lowland Amazonia was predominantly drier (e. g. Haffer 1969; van der Hammen 1974), colder (Colinvaux 1987; Liu and Colinvaux 1988) or both, and how this affected the Pleistocene distribution of tropical forest, remain hotly contested (Colinvaux 1987; Rasanen, Salo and Kalliola 1991). Although most of the corroborative geomorphological evidence for dry periods in the tropical lowlands during the Pleist ocene is now otherwise interpreted (Irion 1989; Colinvaux 1987), some new data look promising. There are also several other theories that attempt to explain aspects of present biogeography on the basis of past geological events, including river-channel formation and migration (Capparella 1988; Salo et al. 1986; Salo and Rasanen 1989), hypothesized massive flooding in south-western Amazonia (Campbell and Frailey 1984), and the formation of a putative giant Pleistocene lake in Amazonia (Frailey et al. 1988). Mesoamerica For its size, Middle America is even more complex geologically than South America (see Central America regional overview). Nuclear Central America, an integral part of the North American continent, reaches south to central Nicaragua. The region from southern Nicaragua to the isthmus of Darien in Panama is geologically younger and presents recent volcanism, uplift and associated sedimentation. Like South America, the northern neotropics have a mountainous spine that breaks into separate cordilleras in the north. In general the Middle American cordilleras are highest to the north in Mexico, and lowest in Panama to the south-east. In Mexico, the geological picture is complicated by a band of volcanoes that bisects the continent from east to west at the latitude of Mexico City. This eje volcanico transversal is associated with the Mexican megashear, along which the southern half of the country has gradually moved eastward with respect to the northern half. In southern Central America, volcanism has been most intensive in Costa Rica, which has two sections of its Central Cordillera reaching above treeline. In northern Costa Rica and adjacent Nicaragua the volcanoes become gradually reduced in size and more isolated from each other to the north. Similarly in Panama the Central Cordillera is over 2000 m high to the west near the Costa Rican border but only about 500 m high in most of the eastern part of the country. In central Panama, the Panama Canal cuts through a continental divide of only 100 m elevation, and in the San Juan River/Lake Nicaragua area of Nicaragua the maximum elevation is even less. For montane organisms, these interruptions in the cordillera represent major biological discontinuities. The Yucatan Peninsula area of Mexico, Guatemala and Belize represents a geologically anomalous portion of Middle America. It is a flat limestone formation more like the Greater Antilles or Peninsular Florida than the mountainous terrain and volcanic soil of most of Middle America. Limestone is otherwise relatively rare in the continental neotropics, in contrast to many other parts of the world, with small outcrops like those in the Madden Lake region of central Panama or the Coloso area of northern Colombia being associated with peculiar floras. These areas, like the Yucatan Peninsula, tend to show distinctly Antillean floristic affinities, paralleling the geological ones. Caribbean The Antillean islands constitute the third geologic unit of the neotropics (see Caribbean Islands regional overview). The Antilles make up in geological complexity what they lack in size. The most striking geological anomaly is Hispaniola, which is a composite of what were three separate islands during much of the Cenozoic. In addition to being completely submerged during part of the midCenozoic, the southern peninsula of Hispaniola was probably attached to Cuba instead of Hispaniola until the end of the Cenozoic. Jamaica too was completely submerged during much of the mid-Cenozoic, and has a different geological history from the rest of the Greater Antilles, with closer connections to Central America via the nowsubmerged Nicaraguan Rise. Possibly a collision of the western end of the Greater Antilles island arc with Mexico-Guatemala fragmented its western end to form Jamaica. Also phytogeographically and conservationally important, some of the Antilles have extensive areas of distinctive substrates. In addition to large areas of limestone, most of the Greater Antilles (Cuba, Hispaniola, Puerto Rico) have significant areas of serpentine and other ultrabasic rocks formed from uplift of patches of oceanic crust during the north-eastward movement of the Caribbean plate. The Lesser Antilles are small and actively volcanic. Most of the other smaller islands are low limestone keys with little or no geological relief. These patterns are clearly reflected in the Antillean flora. The most striking concentrations of local endemism occur in areas of ultrabasic rocks or on unusual types of limestone on the larger islands. The Lesser Antilles, Bahamas and other smaller islands have only a depauperate subset of the generally most widespread Antillean taxa. Vegetation The neotropics include a broad array of vegetation types commensurate with their ecological diversity. Along the west coast of South America are both one of the wettest places in the world Tutunendo in the Choco region of Colombia, with 11,770 mm of annual precipitation, and the driest no rain has been recorded in parts of the Atacama Desert of Chile. The largest tract of rain forest in the world is in the Amazon Basin, and Amazonia has received a perhaps disproportionate share of the worlds conservation attention. While the forests of Upper Amazonia are the most diverse in the world for many kinds of organisms, including trees as well as butterflies, amphibians, reptiles, birds and mammals, other vegetation types have equal or greater concentrations of local endemism and are more acutely threatened. In particular, the plight of dry forests and of Andean montane forests are beginning to receive increased attention. Some isolated areas of lowland moist forest outside of Amazonia also have highly endemic floras and are currently much more threatened than Amazonia. In the following paragraphs are sketched the major neotropical vegetation types, followed by a conservation assessment of each. At the very broadest level, the lowland vegetation types of South America and the rest of the neotropics may be summarized as: 1. Tropical moist forest (evergreen or semi-evergreen rain forest) in Amazonia, the coastal region of Brazil, the Choco and the lower Magdalena Valley, and along the Atlantic coast of Central America to Mexico. 2. Dry forest (intergrading into woodland) along the Pacific side of Mexico and Central America, in northern Colombia and Venezuela, coastal Ecuador and adjacent Peru, the Velasco area (Chiquitania) of eastern Bolivia, a broad swath from north-west Argentina to north-east Brazil encompassing chaco, cerrado and caatinga, and with scattered smaller patches elsewhere. 3. Open grassy savanna in the pampas region of north-eastern Argentina and adjacent Uruguay and southernmost Brazil, the Llanos de Mojos and adjacent pantanal of Bolivia and Brazil, the Llanos of Colombia and Venezuela, and the Gran Sabana and Sipaliwini savanna in the Guayana region. 4. Desert and arid steppe in northern Mexico, the dry Sechura and Atacama regions along the west coast of South America between 5 °S and 30 °S, and in the monte and Patagonian steppes of the south-eastern part of the Southern Cone of South America. 5. The Mediterranean-climate region of central Chile. 6. The temperate evergreen forests of southern Chile with an adjacent fringe of Argentina. More complex montane formations occur along the Andean Cordillera which stretches the length of the western periphery of South America, in the more interrupted Central American/Mexican cordilleran system, in the tepuis of the Guayana region and in the coastal cordillera of southern Brazil. Moist and wet forests In general, forests receiving more than 1600 mm (Gentry 1995) or 2000 mm (Holdridge 1967) of annual rainfall are evergreen or semi-evergreen and may be referred to as tropical moist forest. In the neotropics, lowland tropical moist forest is often further subdivided, following the Holdridge life-zone system, into moist forest (2000-4000 mm of precipitation annually), wet forest (4000-8000 mm) and pluvial forest (over 8000 mm). Nearly all of the Amazon Basin receives 2000 mm or more of annual rainfall and constitutes variants of the moist forest. There are also several major regions of lowland moist forest variously disjunct from the Amazonian core area. These include the region along the Atlantic coast of Central America (extending into Mexico), the lower Magdalena Valley of northern Colombia, the Choco egion along the Pacific coast of Colombia and northern Ecuador, and the coastal forests of Brazil. Lowland moist forest is the most diverse neotropical vegetation type, structurally as well as taxonomically. In most lowland moist-forest and wet-forest regions around a quarter of the species are vines and lianas, a quarter to a half terrestrial herbs (including weeds), up to a quarter vascular epiphytes and only about a quarter trees (Gentry and Dodson 1987; Gentry 1990b). To the extent that smaller organisms such as herbs and epiphytes may demand different conservation strategies than large organisms like trees (or top predators), this habitat diversity assumes conservation importance. Diversity patterns are also important for conservation planning. There is a strong correlation of plant community diversity with precipitation wetter forests generally are more botanically diverse. For plants the most speciesrich forests in the world are the aseasonal lowland moist and wet forests of Upper Amazonia and the Choco region. For plants over 2. 5 cm dbh in 0. 1-ha samples, world record sites are in the pluvial-forest area of the Colombian Choco (258-265 species); for plants over 10 cm dbh in 1-ha plots, the world record is near Iquitos, Peru (300 species out of 606 individual trees and lianas). Concentrations of endemism do not necessarily follow those of diversity. Local endemism appears to be concentrated in cloud-forest regions along the base of the northern Andes and in adjacent southern Central America (cf. Vazquez-Garcia 1995), and in the north-western sector of Amazonia where the substrate mosaic associated with sediments from the Guayana Shield is most complex (Gentry 1986a). Overall regional endemism in predominantly moist-forest areas is greatest in Amazonia, with an estimated 13,700 endemic species constituting 76% of the flora (Gentry 1992d). However many of these species are relatively widespread within Amazonia. The much more restricted (and devastated, see below) Mata Atlantica forests of coastal Brazil have almost three-quarters as many endemic species (c. 500) as Amazonia and similarly high endemism (73% of the flora) (Gentry 1992d). Moreover a larger proportion of the Mata Atlantica species probably are locally endemic. On the other side of South America, the trans-Andean very wet to wet and moist forests of the Choco and coastal Ecuador are also geographically isolated and highly endemic (cf. Terborgh and Winter 1982). Estimates of endemism in the Choco phytogeographic reg ion are c. 20% (Gentry 1982b). Probably about 1260 or 20% of western Ecuadors 6300 naturally occurring species also are endemic (Dodson and Gentry 1991). For the northern Andean region as a whole, including both the coastal lowlands of western Colombia and Ecuador and the adjacent uplands, Gentry (1992d) estimated over 8000 endemic species, constituting 56% of the flora. Moreover this is probably the floristically most poorly known part of the neotropics, perhaps of the world, surely with several thousand mostly endemic species awaiting discovery and description. Dry forests There are seven main areas of dry forest in the neotropics, and by some estimations this may be the most acutely threatened of all neotropical vegetations. The interior dry areas of South America are outstanding in their regional endemism, estimated at 73%. Two of the most extensive neotropical dry-forest areas represent manifestations of the standard interface between the subtropical high pressure desert areas and the moist equatorial tropics. In Middle America, this area of strongly seasonal climate occurs mostly along the Pacific coast in a narrow but formerly continuous band from Mexico to the Guanacaste region of north-western Costa Rica. There are also outliers farther south in the Terraba Valley of Costa Rica, Azuero Peninsula of Panama, and even around Garachine in the Darien (Panama), partially connecting the main Middle American dry forest with that of northern South America. These western Middle American dry forests are made up almost entirely of broadleaved deciduous species. In addition, the northern part of the Yucatan and large areas of the Antilles are covered by dry-forest variants. Most of the Caribbean dry forests are on limestone, and their woody species tend to be distinctively more sclerophyllous and smaller leaved than are the Pacific coast dry-forest plants. In the driest areas, both these types of dry forest tend to smaller stature and merge into various kinds of thorn-scrub matorral. In South America, only the extreme northern parts of Colombia and Venezuela reach far enough from the Equator to enter the strongly seasonal subtropical zone. Floristically and physiognomically this northern dry area is very much like similarly dry areas of western Middle America. The strongly seasonal region of northern South America also includes the open savannas of the Llanos extending from the Orinoco River west and north to the base of the Eastern Cordillera of he Colombian Andes and the north slope of the Coast Range of Venezuela. Large areas of the lowlying, often poorly drained Llanos are seasonally inundated, especially in the Apure region. The main area of tropical dry forest in South America is the chaco region, encompassing the western half of Paraguay and adjacent areas of Bolivia and Argentina, south of 17 °S latitude. The chaco is physiog nomically distinctive in being a dense scrubby vegetation of mostly smallleaved, spiny branched small trees interspersed with scattered large individuals of a few characteristic species of large trees. To the south, the chaco gives way to the desert scrub of the Argentine monte. There is a distinctive but generally neglected area of dry forest at the interface between the chaco and Amazonia in Bolivia. The names Chiquitania and Velasco forest have been used locally in Bolivia to refer to this vegetation, which extends from the Tucuvaca Valley and Serrania de Chiquitos in easternmost Santa Cruz Department interruptedly westward to the base of the Andes and along much of the lower Andean slopes of the southern half of Bolivia. This region of closed-canopy dry forest is physiognomically similar to that of western Central America, with tall broadleaved completely deciduous (caducifolious) trees. Although it has been locally regarded as merely representing the transition between the chaco and Amazonia, it is a floristically and physiognomically distinctive unit that should be accorded equivalent conservation importance to the other major dry-forest vegetation types (Gentry 1994). The chaco is adjoined to the north by two large and phytogeographically distinctive areas of dry forest, the cerrado and caatinga, which cover a small portion of easternmost Bolivia and most of the Brazilian Shield area of central and north-eastern Brazil. The typical vegetation of the cerrado region consists of wooded savanna with characteristically gnarled sclerophyllous-leaved trees with thick twisted branches and thick bark, widely enough separated to allow a ground cover of grass intermixed with a rich assortment of woody-rooted (xylopodial) subshrubs. The cerrado also includes areas where the trees form a nearly closed canopy (cerradao), and large open areas of grasses and subshrubs with no trees at all (campo limpio and campo rupestre). Although the cerrado is appropriately considered a kind of dry forest, some cerrado regions actually receive more rainfall than do adjacent forest regions; excess aluminium in the soil may be as important as the climate in determining its distribution. The even drier forest of the caatinga of north-eastern Brazil extends from an appropriately subtropical 17 °S latitude farther north to a surprisingly equatorial 3 °S. Why this region should have such low rainfall remains poorly understood. Another climatic peculiarity is the irregularity of its rainfall, not only with low annual precipitation, but also with frequent years when the rains fail almost completely. The typical vegetation of the caatinga relatively low, dense, small-leaved and completely deciduous in the dry season is physiognomically similar to that of the chaco. The final major South American dry-forest area is the coastal forest of north-western Peru and south-western Ecuador. Even more anomalous in its geographical setting than the caatinga, this dry-forest region is positioned almost on the Equator. The occurrence of dry forest so near the Equator is due to the offshore Humboldt Current. While similar cold-water currents occur along mid-latitude western coasts of other continents, the Humboldt Current is perhaps the strongest of these and is the only cold current reaching so near the Equator. The dry forest of coastal Peru and adjacent Ecuador is (or at least was, see below) physiognomically similar to that of western Central America, tall with a closed canopy of broadleaved completely deciduous trees. There also are a number of scattered smaller patches of tropical dry forest and/or savanna in various interAndean valleys, around Tarapoto, Peru, the Trinidad region of Bolivia, Brazils Roraima area, the Surinam/Brazil border region, on Marajo Island, and in the pantanal region of the upper Paraguay River. Grasslands and deserts Grasslands and deserts occupy smaller areas of the neotropics than they do in Africa or most higher latitude continents. The main grassland region of the neotropics is the pampas region between about 39 °S and 28 °S and encompassing most of Uruguay as well as adjacent eastern Argentina and southernmost Brazil. The other major grassland area is the llanos region of Colombia and Venezuela. Smaller predominantly grassland regions occur in north-eastern Bolivia (Llanos de Mojos) and the south-eastern Guayana region (Gran Sabana and Sipaliwini savanna). There are also areas with few or no trees and dominated by grasses in the cerrado and pantanal regions of Brazil, and scattered outliers associated with local edaphic peculiarities elsewhere. None of the major grassland regions has many endemic species, in contrast to the campos rupestres of the Brazilian Shield and the Guayana area whitesand savannas, which have many endemics. This contrast is especially marked in southern Venezuela where some savanna patches have clay soils and a llanos-type flora of widespread species, whereas others have sandy soils and a flora of Amazonian affinities with many endemic species (Huber 1982). The desert regions of Latin America are confined to northern Mexico, the monte (Morello 1958; Orians and Solbrig 1977) and Patagonian steppes of Argentina, and the narrow Pacific coastal strip of northern Chile and Peru. The 3500-km long South American coastal desert is one of the most arid in the world most of it is largely devoid of vegetation. This region is saved from conservational obscurity, however, by the occurrence of islandlike patches of mostly herbaceous vegetation in places where steep coastal slopes are regularly bathed in winter fog. Although these lomas formations are individually not very rich in species (mostly fewer than 100 spp. ), they have a very high degree of endemism due to their insular nature. The overall lomas flora includes nearly 1000 species, mostly annuals or geophytes. Diversity and endemism in the lomas formations generally increase southward, where cacti and other succulents are also increasingly represented (Muller 1985; Rundel et al. 991). Montane vegetation The main montane-forest area of the neotropics is associated with the Andes. A major but more interrupted montane-forest strip is associated with the mountainous backbone of Central America. Venezuelas Cordillera de la Costa phytogeographically is essentially an Andean extension, although geologically distinct from the Eastern Cordi llera of the Colombian Andes. The tepui summits of the Guayana Highlands, though small in area, constitute a highly distinctive and phytogeographically fascinating montane environment. The Serra do Mar along Brazils south-eastern coast is mostly low elevation but has a few peaks reaching above treeline with a depauperate paramo-like vegetation. The Andes may be conveniently recognized in three segments: northern Venezuela, Colombia and Ecuador; central-Peru and Bolivia; and southern-Chile and Argentina. In general the northern Andes are wetter, the central and southern regions drier. The main biogeographic discontinuity in the Andean forests is associated with the Huancabamba Depression in northern Peru, where the extensive system of dry interAndean valleys of the Maranon River and its tributaries entirely bisects the Eastern Cordillera and is associated with a topographically complex region having unusually high local endemism. Treeline in the tropical Andes occurs around 3500 m, depending on latitude and local factors. Above treeline, the wet grass-dominated vegetation of the Venezuelan, Colombian and northern Ecuadorian Andes is termed paramo; this drier vegetation, occurring from Peru to Argentina and Chile, is the puna. Colombian and Venezuelan paramos are characterized by Espeletia (Compositae) with its typical pachycaul-rosette growth form. The vegetation above treeline of most of Ecuador and northernmost Peru, locally called jalca in Peru, is ecologically as well as geographically intermediate; although generally called paramo in Ecuador, this region lacks the definitive Espeletia aspect of the typical northern paramos. While individual high-Andean plant communities are not very rich in species, many different communities can occur in close proximity in broken montane terrain. Thus the se
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