THE AMAZONIAN LOWLANDS, which comprise the states of Amazonas, Para, and part of Maranhao, consist in the main of Tertiary and Quaternary material. The rainfall is heavy, and the rivers overflow their banks and flood the surrounding country for a considerable period each year. Owing to the great precipita tion and subsequent evaporation the heat never becomes excessive, the summer and winter means for Manaos being 82•° F. and 80•° F. respectively. The soil of the whole region is generally fertile, and the vegetation, both in the vicinity of the rivers and on the intervening lands, is dense.
Under such conditions agriculture is practically impossible, and the chief products are those of the tropical forest. Caoutchouc, or rubber, which holds the first place, is obtained from several varieties of Hevea, Hevea brasiliensis producing the best quality when it is grown under the most favourable conditions, that is, on land which is flooded for a considerable part of each year. As rubber trees do not grow in close formation, but are scattered throughout the forest, there are no plantations in the proper care and develop ment of which the owners take a genuine interest. The result is that reckless destruction is indulged in by the seringueiros, whose sole object is to obtain the maximum amount of rubber ; and every year they are compelled to go further and further from the main streams, where the trees have ceased to be productive, and to enter the smaller tributaries, where the rubber is obtained at greater cost and greater risk. At present the amount which is obtained from plantations in the Amazon lowlands is negligible, and the prospects of a substantial increase in this respect are not bright. The population is small—less than one to the square mile—and consists largely of Indians, or of immigrants of mixed white and Indian blood from Ceara, while the climatic conditions of the region are such as to deter European peoples from engaging in manual labour within it. In addition to the product of Hevea
brasiliensis, known on the market as Para rubber, caoutchouc is extracted from several other trees in the Brazilian forest. Of these, the most important are Manihot, from which Ceara rubber, next in quality to Para, is obtained, and Mangabeira, which yields an inferior article used for covering cables and similar purposes.
Manaos, at the confluence of the Amazon and the Rio Negro, is the collecting point for rubber in the interior, and Para, on the Tocantins, the port from which it is sent abroad. The production of rubber in the basin of the Amazon during the years 1907-8-9-10, averaged 38,000 metric tons per year, or over 55 per cent. of the world's supply. Of this, about 35,000 tons came from the Amazonian lowlands in Brazil.
Among other important products of this region are Brazil nuts, cacao, and timber. Cacao has, with the development of the rubber industry, become of less importance than formerly, The trees grow wild, and only a few plantations exist ; but one-seventh of the whole Brazilian crop of cacao comes from this region. It is remarkable that towns like Manaos and Para, situated in the great selvas of South America, should import more timber than they export, but it is explained by the great diversity of trees in the forest, the enormous amount of undergrowth, the scarcity of labour, and the hardness of the wood which renders it unsuitable for many purposes. Cedar forms the principal export.