A model of shifting cultivation: can soil conservation reduce deforestation?
研究了轮垦中土壤保护与森林砍伐的关联，发现改善土壤保护比促进非农活动更能减少森林砍伐，而农业补贴或降低贴现率反而会加剧砍伐。
Abstract Shifting cultivators manage soil not only by adjusting soil use on already‐cleared lands, as in continuous cultivation, but also by clearing forests to obtain new fertile soils. This study examines the crucial link between on‐farm soil conservation and deforestation in shifting cultivation by modeling forest clearing as an investment in soil for a private farmer. More generally, by doing so the study attempts to integrate deforestation and soil conservation models which have been separately developed in the literature. Our policy goal is to arrest tropical deforestation—as destruction of global commons—caused by land degradation in shifting cultivation while improving the well‐being of poor shifting cultivators. Our integrated approach enables joint policy analyses of deforestation and land degradation. Three welfare‐enhancing policies are considered. The first is agricultural and nonagricultural subsidies affecting farm and nonfarm income opportunities. The second is fiscal and tenure policies affecting discount rates. Our question is whether the link between forest clearing and soil fertility alters the outcomes of these two standard macroeconomic policies commonly found in the literature. The third policy (or program) is various soil conservation measures affecting soil regeneration and erosivity on already‐cleared lands. This article examines a very important question which has received little attention in previous theoretical works: can soil conservation reduce deforestation? This study confirms anti‐deforestation effects of the promotion of nonfarming activities—a common and often emphasized finding in previous works—among shifting cultivators. More importantly, it also demonstrates that improving various soil conservation measures not only discourages forest clearing among shifting cultivators but also tends to have greater effects on forest protection than promoting nonfarming activities. Contrarily, agricultural price subsidy or technological progress gives rise to the opposite outcome, and lowering the farmer's discount rate or improving tenure security encourages him/her to clear more forests just to accumulate soil.