Tropical Rain Forest Regions of South America are not very easily accessible to human beings due to the presence of dense forests. Lack of adequate Transport and communication facilities, presence of nomadic aboriginal natives are some other reasons why people doesn't migrate to South American Tropical forests. Unbearable climatic conditions, scarcity of food and water, scarcity of adequate transport and communication facilities are some of the reasons why the growth of settlements with large populations is limited in Sahara desert.