Carbon sequestration by blue carbon (carbon captured by marine living organisms) in port areas would generate benefits and social values. Futhermore, CO₂ emissions due to port (coastal shallow water) use changes are potentially obligated to be quantitatively reported if such projects are included in the national inventory in the next framework of the international climate change initiatives after 2020. Therefore, development of the measurement methodology for CO₂ emission/absorption and preparation of the guideline in terms of blue carbon are critical.
　In this article, a blue carbon guideline is proposed. We focus on the measurement methods for (1) reference level, (2) project area, and (3) CO₂ emission/absorption and carbon sequestration per unit area (air-water CO₂ exchanges and the carbon stocked in organisms and sediments) in port areas.Data reliability, technical ease, and cost are chosen as the evaluation criteria in light of the implemention and prevalence of the blue carbon initiatives as an option for the future climate change mitigation.