In contrast to the scrublands that border it to the south, the Amazonian rainforest and the waters that drain it have a remarkable abundance of plant and animal life, even though the ecosystem is a fragile one that can easily be destroyed. While giving the impression of monotony because of the apparently similar tree crowns that rise to a more or less uniform height of around 150 to 200 feet, these lands contain the greatest variety of plant species on Earth–many thousands, less than half of which have been identified.
Furthermore, serving as a defense mechanism against blight and other natural enemies, individual plants of any species tend to be widely dispersed. A typical acre of forest in the Amazon may contain 250 or more tree species, compared, for example, with perhaps a dozen in any acre of woods in the northeastern United States.
Because the crowns of these forest giants form a virtually closed canopy, allowing 10 percent or less of the sunlight to filter through, there is little plant or animal life on the ground below.
The trees, however, are festooned with a wide variety of epiphytes, bromeliads, and lianas, while their branches teem with animal life, from insects, snakes, and tree frogs to numerous species of monkeys and a bewildering variety of birds. Some 1,400 bird species have been identified in the immediate vicinity of the main stream of the Amazon alone, both in the treetops and within the complex ecosystem of the vrzea, the riverine lands. There, along the riverbanks, are also found alligators, anacondas, boa constrictors, capybaras, and a number of lesser reptiles and mammals.
In the waters themselves there are manatees, freshwater dolphins, and some 1,500 identified species of fish, with perhaps another 1,000 unidentified species; the variety includes many types of piranhas, not all of them flesheating, electric eels, and some 450 species of catfish.
The Amazon is also home to the world's largest fresh-water turtle, of the genus Podocnemis, extinct everywhere except there and on the island of Madagascar. Weighing an average of 150 pounds (70 kilograms), these turtles were once a mainstay of the Indian diet, and they remain a highly prized food source. Although the turtles were placed on the endangered species list, illicit turtle meat has continued to be an available delicacy.
The settlement of what is now Brazil began many thousands of years ago with the arrival of the first tribes of Paleo-American Indians, migrants from North America who were probably of Asian origin. Nomadic hunters and gatherers, they inhabited the less hospitable parts of the country away from the larger rivers. By the time of the European arrival a second group had evolved, known collectively as the tropical forest Indians. Outnumbering the nomadic Indians, they were skilled farmers and fishermen who occupied the best lands of the Amazon and Paraguay river systems and most of the coastal plains, making up the bulk of the more than 2,000,000 native inhabitants of Brazil at the time of the European arrival.
The first European occupants of Brazil, around the beginning of the 16th century, settled among the coastal Indian villages or at the trading posts that were established at Salvador and Cabo Frio. They exchanged hardware and trinkets with the Indians for brazilwood, which was used for making a rich, fire-coloured dye (brasa is the Portuguese word for "live coals"). By the second half of the 16th century sugarcane became dominant in the colonial economy, giving rise to a scattering of urban centres, among which Olinda and Salvador were the most important. By this time the coastal Indians had been decimated, and slaves from Africa were imported to work on the rapidly expanding plantations.
The Southeast is Brazil's most densely populated region. During the first two centuries of Brazilian colonization little attention was paid to the nearly inaccessible and seemingly unproductive highlands, although parties of explorers, known as bandeirantes, did traverse them from time to time, capturing Indians for slaves and searching for precious metals and stones. Taking with them a few head of cattle, which eventually expanded into the herds that came to dominate the economy from the caatinga to the Pantanal, some of the bandeirantes settled down in the interior and continued their search for gold and diamonds. The first gold strike came in what is now Minas Gerais in 1695, where diamonds were also found in 1729, attracting many plantation owners from the northeast who brought their slaves. They spent money lavishly on building fine towns, such as Ouro Prto and Diamantina, and also invested in small industries to supply the mines as well as the farms that, before long, were producing a surplus for export. With the development of roads over the Serra do Mar to the coast, and the transfer of the colonial capital from Salvador to Rio de Janeiro in 1763, Brazil's economic and political centre shifted from the northeastern to the southeastern part of the country. Subsequently, during the 19th century, this was consolidated by the wealth generated by the great coffee plantations developed in the Paraba do Sul valley.
Rio de Janeiro's population had passed 500,000 by the time the slaves were fully emancipated in 1888, while the city of So Paulo, entrept for all of Brazil south and west of Minas Gerais, was but a modest town of 65,000. That situation changed as a flood of European immigrants flocked to Brazil; some worked as tenants on the coffee plantations that were expanding across the terra roxa soils of So Paulo and northern Paran, while others established themselves on small freeholds along the southern coast and in the forests. Whereas the latter group remained physically and culturally isolated until after World War II, the newcomers in So Paulo played a key role in building the railroads and establishing the industries that were later to give both the city and the state their preeminence in the Brazilian economy.
While the more southerly parts of Brazil were expanding economically, the northeast was stagnating and beginning to feel the effects of overpopulation and an archaic landholding system under which all the best coastal lands were in the hands of a few powerful landowners. This had driven the earlier population of mixed Indian and European ancestry, the mestizos, ever deeper into what was then the serto, or outback. They first settled the agreste and then the caatinga, wherever water or a small patch of moist ground was available. Severe droughts in the 1870s and 1880s forced many of these people to abandon their land, and they were recruited to tap rubber trees in the Amazon to supply the growing demand for this product. Half a century was to elapse before there were new opportunities for massive migrations from the drought-prone, impoverished northeastern region. One of these opportunities was to provide the large amount of labour that was required during the post-World War Il period to build the constantly expanding urban centres of the southeastern region, culminating in the construction of Braslia. At the same time, northeasterners began occupying the sparsely populated forest lands along the remote northern perimeter of the Brazilian Highlands, including Rondnia and Acre. There they have been joined by emigrants from southern Brazil, who were displaced by agricultural mechanization.
The Amazon region in the north remains the most underpopulated part of Brazil, with an environment resistive to commercialization and settlement despite government development plans intended to lure more migrants. There has been a damaging trend to the ecology, nevertheless. Forestry and cattle raising, for instance, pose threats to the future of the rainforest and the Amazonian habitat.
The entire Amazon region had a population of only about 40,000 in the middle of the 19th century, but by the end of World War I this had risen, largely owing to an earlier rubber boom and the influx of northeasterners, to some 1,400,000; Belm and Manaus had grown from somnolent villages into modest-sized cities. In the late 1950s there was a minor boom along the Lower Amazon where Japanese settlers began raising jute and black pepper. The manganese deposits in Amap were also being rapidly developed, and a new pioneer zone appeared along a highway between Belm and Braslia.
With its rural settlement patterns essentially defined, Brazil in the post-World War II period began a headlong drive toward industrialization, which turned the nation from an essentially rural society into one in which three-fourths of the population is urban. In 1940 less than one-third of the total population of 42,000,000 lived in urban areas; by the late 20th century more than that number lived in the So Paulo metropolitan area alone. Rio de Janeiro has the second largest metropolitan population, and other major metropolitan areas include Belo Horizonte, Salvador, Fortaleza, and Braslia. Somewhat smaller are Recife, Curitiba, Prto Alegre, and Belm. This rapid growth has led to a series of physical and social problems, while the demand for housing has raised land values to staggering heights. As a result, members of the middle class have been forced more and more to live in minuscule apartments in densely packed high-rises, while the poor are confined to shantytowns, socalled favelas, or in more distant developments that may be several hours away from the workplace.