Application of the Ocean Health Index to assess ecosystem health for the coastal areas of Shanghai, China

•Ocean Health Index is used to assess the ecosystem health of Shanghai’s ocean.•Some parameters and reference points were adjusted to apply OHI at the city scale.•Clean Water and Fisheries scored the lowest and have also been declining.•This research provides experience on applying OHI to other coastal areas. The ocean delivers many ecosystem services to human society in providing food, livelihoods, and recreation and is crucial for regulating the global climate. Coastal cities, which have become the backbone of national economies, are highly dependent on the ecosystem services supported by the ocean. As a global coastal megacity, Shanghai has benefited enormously from its relationship with the ocean but its burgeoning population and rampant economic development in recent decades have applied great pressures on the associated coastal ecosystems and have reduced the ocean's capacity to provide ecosystem services and, meanwhile, have led to the demand for greater investment in ocean ecosystem restoration. To support the goal of long-term sustainability and facilitate appropriate management decisions, it is essential to assess the current health status of the coastal ecosystems of Shanghai and evaluate potential future risks. Here we apply the Ocean Health Index (OHI) framework, with indicators and reference points adjusted based on the unique coastal environment in Shanghai. The results reveal that the city obtained an overall OHI of 59 (out of 100) for the period 2012 to 2016. Individual indicators for Clean Waters (22) and Fisheries (39) exhibit particularly low values, indicating that the coastal waters around Shanghai are heavily polluted and that marine fishing is unsustainable. The city’s highest OHI scores are in the sectors of Coastal Livelihoods and Economies (93), and Tourism and Recreation (93), indicating that Shanghai’s coastal ecosystems contribute significantly to people’s livelihoods and regional economies, while marine recreational areas and related leisure activities add considerably to the quality of life in the region. This study demonstrates the value of the OHI in assessing ocean health at the city scale and reveals its potential for application in other coastal localities. In so doing, the findings provide a valuable benchmark against which to measure progress towards the sustainable development of Shanghai's oceans.