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Shellfish reef ecosystems in Australia have been greatly depleted. Building on earlier trials, a continent-scale restoration initiative was underway by 2019 to restore 30% of their former distribution. Integral elements of building and progressing this ecoscape-scale restoration program are outlined and challenges discussed. Documenting pathways and challenges to large-scale restoration informs global commitments to see 30% of degraded ecosystems under effective restoration by 2030.

The global loss of coastal habitats is putting communities at risk of erosion and flooding, as well as impacting ecosystem function, cultural values, biodiversity, and other services. Coastal habitat restoration can provide a nature-based solution to the increasing need for climate adaptation on the coast while recovering lost ecosystems. Despite the benefits of using nature-based coastal protection to manage coastal hazards, there are scientific, socio-political and economic barriers to the broad use of this approach. Understanding the details of these barriers from the perspective of multiple stakeholders is essential to identifying solutions to overcome them. Using a workshop with participants that are key partners and stakeholders (from government, engineering consulting firms, and non-governmental organisations) in the management, design, and delivery of a coastal protection solution we aimed to: (1) gain a better understanding of the barriers faced by multiple stakeholders involved in the implementation of nature-based coastal protection; and (2) identify tangible solutions to these barriers to increase or support implementation, help focus attention on areas for future research, and inform pathways forward for the governance of nature-based coastal protection. We defined 19 barriers to nature-based coastal protection, but the primary ones that are experienced during the delivery of a project are a lack of: education and awareness; community support; necessary expertise and technical guidance; and uncertainty around: the risk reduction that can be achieved; planning and regulatory processes; and ownership of the structure. Two barriers that do not persist during the design stages of a project but are overarching as to whether nature-based coastal protection is considered in the first place, are government support and the availability of funding. The importance of these primary barriers changes depending on the method of nature-based coastal protection. We conclude by identifying both immediate actions and long-term solutions for enabling nature-based coastal protection in response to each of the primary barriers.

Shellfish reefs have been lost from bays and estuaries globally, including in the Swan-Canning Estuary in Western Australia. As part of a national program to restore the ecosystem services that such reefs once provided and return this habitat from near extinction, the mussel Mytilus galloprovincialis was selected for a large-scale shellfish reef construction project in this estuary. To assess the potential filtration capacity of the reef, estuary seston quality, mussel feeding behavior, and valve gape activity were quantified in the laboratory and field during winter and summer. In general, estuary water contained high total particulate concentrations (7.9–8.7 mg L−1). Standard clearance rates were greater in winter (1.9 L h−1; 17 °C) than in summer (1.3 L h−1; 25 °C), the latter producing extremely low absorption efficiencies (37%). Mussel valves remained open ~97% and ~50% of the time in winter and summer, respectively. They often displayed erratic behavior in summer, possibly due to elevated temperatures and the toxic microalgae Alexandrium spp. Despite numerous stressors, the reef, at capacity, was estimated to filter 35% of the total volume of the estuary over winter, incorporating 42.7 t of organic matter into mussel tissue. The reefs would thus make a substantial contribution to improving estuary water quality.