250 FACTS ABOUT CROP TREES
commercial utilization, but capable of it, and at the same time capable of improvement through plant breeding.
TROPICAL NEEDS AND THE EROSION PROBLEM
Certain parts of the tropical world are in need of having tree crops developed even more extensively than at present. In a large part of the tropical world the main food supply of native peoples is some cereal. The system of production is to burn the forests, plant a crop or two of corn, and after harvest let the thicket grow again while another piece of land is cleared and burned to make a fresh field. This method destroys the forests. It devastates the soil. If a permanent field is made, the destruction is often even more sure and final. The torrential character of most tropic rainfall lifts field erosion to the plane of an economic terror."
The soil destruction in India and Central America described by the papers just referred to shows that the tropic denizens _ are destroying their lands almost as rapidly with cereals as we are destroying ours in the southern part of the United States with corn, cotton, tobacco, and gullies, and like ourselves they are in need of development of tree-crop agriculture if the lands are to continue to serve the race.
TREE CROPS AND TROPIC FAMINE
On both sides of the equator in latitude varying from six to ten or twelve degrees, the rainfall is concentrated into one season, and as a result the forest gives way to open parklike country called savannah, where trees are scattered over the grasslands. As distance from the equator increases, the rainfall, trees, and grass diminish until finally the desert prevails.
7 See (1) Bulletin of Agricultural Research Institute. Pusa. No. 53. Calcutta, 1916. "Soil Erosion and Surface Drainage." Albert Howard.
(2) "Afforestation of Ravine Lands in Etawah District. United Provinces," E. A. Smythies. Indian Forest Records. Calcutta, 1920.
_ (3) Proceedings of the Second Pan-American Scientific ss. Sec tion 3. Conservation of Natural Resources. O. F. Cook, p. 573. "Possibilities of Intensive Agriculture in Tropical America."
