Soil erosion, poverty and sustainability: A biophysical model of a rural Philippine economy

The Philippine government has committed to sustainable development of the country's agricultural sector as a key strategy for rural poverty reduction. The ability of the rural sector to develop sustainably must be quantified based on the limitations of the resource base on which it depends. In the Philippines, the most limiting resource is typically the topsoil, which suffers from high rates of erosion.; I built a biophysical, spatially distributed model of agricultural output as determined by topsoil depth and erosion rates on Negros Island, in the central Philippines. The island has a land area of 1.2 million hectares and 3.6 million residents. I used the model to test the ability of the island to feed its residents up to the year 2050. I also tested the ability of the Philippine Medium Term Development Plan (MTDP) proposed by the federal government to increase agricultural output while reducing erosion. Both the erosion and agricultural production portions of the model were calibrated with field data collected on Negros in 2004 and 2005.; Model results indicated that half of the island's land area is eroding at rates greater than 10 metric tons/ha/yr. Over the course of the 90-year model run, this led to more than 416,000 hectares of land area being degraded to the point where agricultural production could no longer be supported. This trend, combined with exponential population growth on the island, would lead to the island not being able to feed its residents by 2045. Moreover, the on-site costs of erosion as predicted by my model would rise to more than 200 US{dollar} per hectare per year by 2050, adjusted for inflation. The MTDP would both reduce agricultural output on Negros and increase erosion, contrary to its two stated goals. If policymakers are serious about development of the agricultural sector and poverty reduction in the Philippines, they will have to focus on lowering population growth rates and promoting low-erodibility, high-value crops.; This type of model should be applied in other areas where the potential for growth is critically dependent on the quantity and quality of the natural resource base.