Economic valuation of cultivated lands as nitrogen removal/effusion sites by newly proposed replacement cost method

摘要

To valuate the multifunctionality economically is effective to make it possible to realize the value for the nation and to compare functionalities among countries of the world. In this paper, the external economies of paddy fields and fallow paddy fields including wetlands as N removal function sites, and of upland fields and orchards as pollution sites are valuated by the newly proposed replacement cost method, by replacing them with construction costs of water quality improvement facilities. In addition, we discuss an agricultural land-use scenario in which cultivated land has no net negative economic effect on the water environment. The results showed that (1) paddy fields and fallow paddy fields including wetlands were respectively valued at 1.2×103 and 2.81×103 JPY m−2 on average as the N removal sites, (2) upland fields had 0.32×103 JPY m−2 on average of economic value, and suggested that paddy fields have an external economic value that compensates for the negative external economic value of upland fields 3.65 times their size.