Agricultural water pollution treatment for efficient water quality improvement in linked terrestrial and marine ecosystems

While it is recognized that marine ecosystems are of vital importance from an ecological as well as an economic perspective, these marine ecosystems are affected by water pollution originating from coastal catchments. The delivery of water pollutants to the marine environment can be reduced through water pollution treatment and, consequently, to warrant sustainable economic development of coastal regions we need to balance the marginal costs from water pollution treatment and the associated marginal benefits from marine resource appreciation. Water pollution treatment costs are, however, significant and, consequently, the question arises to what extent marine water quality improvement can efficiently be pursued through water pollution treatment. In this paper we develop and apply an optimal control approach to explore, analytically as well as numerically, social welfare maximizing rates of water pollution treatment for efficient diffuse source water pollution management in linked terrestrial and marine ecosystems. For the case of diffuse source Dissolved Inorganic Nitrogen water pollution in the Tully-Murray catchment (Queensland, Australia), (wetland) water pollution treatment cost functions as well as marine-based environmental value reductions from marine water pollution are estimated to determine social welfare maximizing rates of water pollution treatment. Provided partial (wetland) treatment costs and positive downstream water pollution costs are considered, results show that limited social welfare gains can be obtained through diffuse source water pollution treatment (wetland restoration) in the Tully-Murray catchment.publishe