Systematizing ecosystem change in coastal social-ecological systems: Perspectives from a multi-stakeholder approach in Nakatsu mudflat, Japan

Coastal social-ecological systems (SES) are essential for the wellbeing of coastal communities and the wider society. However, in many parts of the world coastal SES face rapid change, and ultimately degradation. In this paper we unravel the mechanisms and implications of change in coastal SESmobilising multiple sources of knowledge, including scientific, expert-based and traditional and local knowledge (TLK). We focus on the rapidly changing Nakatsu mudflat in Japan, and combine primary and secondary data elicited through a mixed-method participatory approach that mobilised local stakeholders with different types of engagement with (and knowl-edge of) the mudflat. Through 4 expert interviews and 40 questionnaire surveys we identified the main ecosystem services provided by the mudflat that are perceived to be essential to the wellbeing of the local community. Although practically all respondents identified food provision as an important mudflat ecosystem services, many also pointed to the importance of some cultural (e.g. aesthetic beauty, spirituality, education and knowledge) and supporting services (e.g. habitat provision, sediment formation/retention). Through 8 Focus Group Discussions (FGD) and concept mapping we identified and systematized the underlying direct and indirect drivers of ecosystem change in the Nakatsu mudflat. These include population ageing and shrinking, economic diversification, and technological change that have collectively eroded TLK practices associated with the sus-tainable use of the mudflat. We also identified the mechanisms mediating these drivers and how they unfold in reality. Our study demonstrates that participatory processes engaging multiple stakeholders with different types of knowledge can provide rich and useful information on coastal SES change, which might not be readily obvious from simple headline indicators such as the change in the extent of the SES.