Valuing Soil Conservation Benefits of Agroforestry Practices

摘要

Although advocates of agroforestry have promoted soil conservation as one of its211u001eprimary benefits, empirical estimates of these benefits have been lacking due to 211u001etemporal and spatial complexity of agroforestry systems and soil resource 211u001edynamics. This study aims to reduce this gap by designing and testing a three 211u001estage farm level productivity methodology for economic evaluation of soil 211u001econservation benefits of agroforestry. Stage 1 quantifies the relationship 211u001ebetween soil conservation, agroforestry, and soil quality. In Stage 2, the 211u001eeffects of changes in soil quality on individual household agricultural 211u001eproduction are estimated. Finally, in Stage 3 these changes in production are 211u001evalued at net market prices. The data to test this framework were drawn from two 211u001eUSAID/Government of Philippines projects that introduced contour hedgerow 211u001eagroforestry in the Eastern Visayas, Philippines. Multiple regression analysis is 211u001eused in each stage to establish the relationship between the agroforestry 211u001epractice, soil quality and changes in farm-household income. The value of soil 211u001econservation is measured in terms of the change in net household income which is 211u001ethe true measure of change in the economic welfare of the household. The results 211u001eindicate that agroforestry-related soil conservation does benefit the farmer, 211u001ewith the 'average' farmer gaining 114 pesos annually. This in itself provides 211u001einsufficient incentive for the farmer to invest in agroforestry in this case 211u001ebecause the direct opportunity costs of agroforestry adoption and maintenance 211u001eresult in a negative overall contribution to individual household income. 211u001eHowever, the specific soil conservation benefit calculations do not account for 211u001eseveral significant off-site and on-site benefits external to the individual 211u001ehouseholds. In addition, all long run soil conservation benefits (and 211u001eparticularly improvements in the agro-ecological profile) may not have been 211u001erealized in the short ten year period since the initiation of the agroforestry 211u001eproject. Thus, even though net benefits of agroforestry is negative, there may be 211u001egood reason for society to encourage the farmers to practice agroforestry to 211u001econserve the soil and enhance overall societal welfare.