Conservation status, research, and knowledge of seagrass habitats in World Heritage properties

Climate change is increasingly threatening World Heritage (WH) properties and their Outstanding Universal Value (OUV). Climate change impacts the attributes that collectively contribute to the OUV; these attributes can be natural (e.g., seagrass) or cultural (e.g., monuments). A recent UNESCO report showed that seagrass habitats within WH properties are estimated to hold 25% of the global seagrass blue carbon asset. Globally, seagrass habitats provide a wide range of benefits to adjacent ecosystems and coastal human communities, yet they have been declining due to direct anthropogenic and climate change stressors. However, the UNESCO report did not provide any information about the relative importance of the attribute “seagrass habitats” toward the OUV and associated communities of WH properties, nor about their conservation status. This study builds upon this previous work by assessing the relative importance of seagrass habitats toward the values of WH properties and by reviewing the current knowledge about the conservation status, threats, monitoring, and management of seagrass habitats within WH properties. Seagrass was identified as an attribute of Very High or High importance to 9 of 28 WH properties. Through analysis of UNESCO documents and scientific literature, we highlight the lack of research, monitoring, and management instruments addressing the protection of seagrass from climate change impacts within these 28 WH properties. Notably, climate change threats to WH seagrass habitats are poorly addressed within WH documentation. The insufficient analysis and reporting of climate impacts on seagrass within WH properties point to an underestimation of the value of this marine ecosystem broadly. This study assesses the relative importance of seagrass habitats toward the values of World Heritage properties and reviews the current knowledge about the conservation status, threats, monitoring, and management of seagrass habitats within WH properties. We highlight the lack of research, monitoring, reporting, and management instrument addressing the protection of the 28 identified World Heritage seagrass habitats to climate change. This study points to an underestimation of the value and vulnerability of seagrass to climate change broadly.