Assessment and valuation of ecosystem services of lowland rice agroecosystems in Echague, Isabela, Philippines

Ecosystem services are the benefits people obtain from ecosystem. In lowland rice ecosystems, these include grain yield which has an established market price and other non-marketed ecosystem services such as groundwater recharge, nutrient cycling and biological control of insect pests. The economic values of the non-marketed ecosystem services are not considered in making decisions regarding land use conversion of lowland rice farms to non-agricultural uses. These ecosystem services were estimated, analyzed and valued in NIA [National Irrigation Administration] irrigated and pump irrigated lowland rice farms during wet season 2005 and dry season 2006 in two barangays [villages] of Echague, Isabela [Philippines]. Groundwater recharge, which was estimated based in saturated hydraulic conductivity and growing period with standing irrigation water in the paddy, was 2,421.7 cu m/ha/cropping and valued at P1,307.72/ha/cropping using the price of pumping water from the creek as replacement cost instrument. Soil nutrient cycling, which was estimated using the rice straw yield and its nutrient content, consisted of 16.9 kg N/ha, 12.0 kg P2O5/ha and 55.8 kg K2O/ha/cropping valued at P3,103.74/h/cropping using the prices of single element inorganic fertilizers as replacement cost instrument. Biological control of insect pests by spiders expressed in terms of predator-prey ratio was 9:61 and 7:24 in the wet and dry seasons, respectively, with a mean value of P376/ha/cropping using price of insecticides as replacement cost instrument. Rice grain yield was 3,530.7 kg/ha/cropping valued at P35,306.86 using the actual market price. The estimated total ecosystem services value per hectare per cropping was P40,094.32 and P11.5 million/cropping for the whole 286 hectare lowland rice landscape. Meanwhile, most of the value (87.3 percent) constituted the grain yield while only 12.7 percent comprised the three non-marketed ecosystem services. However, such percentage would increase if other non-marketed ecosystem services are assessed and valued. These values were derived using transdisciplinary research method. Agronomy, soil hydrology and insect ecology were used to estimate the magnitudes of ecosystem services, environmental psychology was used to explain why farmers used different farm management practices based on their knowledge, attitudes, perceptions and resources constraints, and resource economics was used to value non-marketed and marketed ecosystem services. Farm management practices affect magnitudes and values of ecosystem services. The economic value of ecosystem services of lowland rice agroecosystems should be shared to farmers and policy makers because these information can serve as basis for policies on lowland rice farm conversion to other land uses.