Subsidence of rice paddy and upland crop fields in Shinotsu Peatland, Hokkaido, Japan

Abstract

Agricultural land use on peatlands inevitably causes ongoing land surface subsidence resulting in a reduction of productivity. In addition, oxidation of the peat substrate associated with subsidence is responsible for greenhouse gas emission with the ensuing consequence for global climatic stability. A concept of “paludiculture”, the utilisation of wet or rewetted peatlands for agriculture, has been proposed in European countries to avoid further subsidence and greenhouse gas emission. However, few studies have documented a long-term record of subsidence through agriculture in wet peatlands such as paddy fields for rice cultivation. In this study, we measured the subsidence rates of peatland in rice paddy use and compared them to the rates in peatland with upland crop cultivation. The average subsidence between 2006 and 2016 for the paddy plots was 3.6±1.9 cm (± SE) and significantly less than that of 25.6±1.7 cm for the upland plots, and the subsidence reduced linearly as the period of paddy use increased. These results suggest that paddy use of peatlands can effectively reduce subsidence. Our results will encourage the use of peatlands with a wet environment as one of the valid options for future peatland management in terms of mitigation of land subsidence and peat loss.