Deforestation, soil dynamics and agricultural development in the tropics

Simeon Kacou Ehui, Purdue University

Abstract

The purpose of this research is to determine the optimal allocation of forest lands in the topics taking into account both the short and long-run impact of deforestation on agricultural productivity. Chapter II develops a theoretical model. Qualitative results are derived, based on a set of testable hypotheses about the nature of the aggregate yield function. In the infinite horizon case, the rate of deforestation will always fall over time along the socially optimal path. Comparative dynamic results indicate that the higher the social rate of discount and the higher returns to agriculture (relative to forestry), the faster the rate of decline in deforestation. This translates into an increase in current deforestation rates relative to future rates. Steady state comparative statics are conducted under the assumption of a quadratic yield function. Results indicate that higher returns to agriculture (relative to forestry) tend to lower the optimal steady state forest stock. The impact of the social rate of discount is indeterminate while technological progress serves to lower the optimal steady state forest stock. In Chapter III, an aggregate yield function is estimated using data from the Ivory Coast. Several key hypotheses about the first and second order derivatives of the aggregate yield function are tested. It is found that yields are increasing in fertilizer use and current period deforestation, but that yields decrease with increases in the stock of deforested lands. Results also indicate that technological progress has accounted for much of the increase in aggregate yields over the past 20 years. Chapter IV provides estimates of the optimal steady state forest stock for the Ivory Coast. When technology is assumed to be stagnant, the forest stock is not completely exhausted in the optimal steady state solution. However, with continued technological change it is optimal to eventually clear all the forest lands. Chapter V uses a discrete time, finite horizon dynamic optimization model to determine the optimal allocation of lands in the Ivory Coast over a 30 year planning horizon. Qualitative results from Chapters II and IV are confirmed by sensitivity analysis and optimal tax rates are computed. The thesis concludes with a discussion of the study's limitations. (Abstract shortened with permission of author.)

Degree

Ph.D.

Advisors

Hertel, Purdue University.

Subject Area

Agricultural economics

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