Estimation of carrying capacity for human populations in a part of the Transamazon Highway colonization area of Brazil / Philip Martin Fearnside.

Tese (Ph.D.)--University of Michigan, 1978.

This study is aimed at estimating carrying capacity for the human population in a portion of Brasil's Transamazon Highway Colonization Area under a variety of assumptions. Special emphasis is given to the effect of variability in a number of factors related to agricultural production and consumption. Carrying capacity is defined operationally in terms of a gradient of increasing probability of colonist failure with population density within a limited range of densities. Both the criteria defining a "failure" and the critical value for the maximum acceptable probability of colonist failure can be culturally defined. Multiple criteria, including both consumption and environmental quality measures can be used. Failure probabilities for carrying capacity estimation are taken to be sustainable over a long period of years. A computer simulation is developed which reproduces many features of the agroecosystem of which the colonists are a part, including sectors for agricultural production, resource allocation, product allocation, and population. Gradients of failure probabilities for the estimation of carrying capacity are constructed from information output by the simulations. Both deterministic and stochastic runs are made, allowing the assessment of the importance of variability. Variability in crop yields results in colonist failure frequencies based on a number of criteria which greatly exceed the goals of Brazilian planners, despite restrictions on the data set which tend to make simulation results over-optimistic. Special emphasis is given in the present presentation to pasture and perennial crops, which are currently viewed by government planners as having potential for long-term sustainable yields both for the small farmers of this study and for large enterprises now being encouraged throughout the Amazon. Although the farming of annual crops is a very risky business as is shown by the data in this study, the simulated results for pasture and perennial crops cast doubt on the presumption of secure and sustainable yields, or these as well. .