Seagrasses are important marine ecosystems situated throughout the world's coastlines. They are facing declines around the world due to global and local threats such as rising ocean temperatures, coastal development and pollution from sewage outfalls and agriculture. Efforts have been made to reduce seagrass loss through reducing local and regional stressors, and through active restoration. Seagrass restoration is a rapidly maturing discipline, but improved restoration practices are needed to enhance the success of future programs. Major gaps in knowledge remain, however, prior research efforts have provided valuable insights into factors influencing the outcomes of restoration and there are now several examples of successful large-scale restoration programs. A variety of tools and techniques have recently been developed that will improve the efficiency, cost effectiveness, and scalability of restoration programs. This review describes several restoration successes in Australia and New Zealand, with a focus on emerging techniques for restoration, key considerations for future programs, and highlights the benefits of increased collaboration, Traditional Owner (First Nation) and stakeholder engagement. Combined,

Marine ecosystems are in a state of crisis worldwide due to anthropogenic stressors, exacerbated by generally diminished ocean literacy. In other sectors, big data and technological advances are opening our horizons towards improved knowledge and understanding. In the marine environment the opportunities afforded by big data and new technologies are limited by a lack of available empirical data on habitats, species, and their ecology. This limits our ability to manage these systems due to poor understanding of the processes driving loss and recovery. For improved chances of achieving sustainable marine systems, detailed local data is required that can be connected regionally and globally. Citizen Science (CS) is a potential tool for monitoring and conserving marine ecosystems, particularly in the case of shallow nearshore habitats, however, limited understanding exists as to the effectiveness of CS programmes in engaging the general public or their capacity to collect marine big data. This study aims to understand and identify pathways for improved engagement of citizen scientists. We investigated the motivations and barriers to engagement of participants in CS using two major global seagrass CS programmes. Programme participants were primarily researchers in seagrass science or similar fields which speak to a more general problem of exclusivity across CS. Altruistic motivations were demonstrated, whilst deterrence was associated with poor project organisation and a lack of awareness of specified systems and associated CS projects. Knowledge of seagrass ecosystems from existing participants was high and gains because of participation consequently minimal. For marine CS projects to support big data, we need to expand and diversify their current user base. We suggest enhanced outreach to stakeholders using cooperatively identified ecological questions, for example situated within the context of maintaining local ecosystem services. Dissemination of information should be completed with a variety of media types and should stress the potential for knowledge transfer, novel social interactions, and stewardship of local environments. Although our research confirms the potential for CS to foster enhanced collection of big data for improved marine conservation and management, we illustrate the need to improve and expand approaches to user engagement to reach required data targets.

The restoration of seagrass habitats is a relatively young field with several successful restoration attempts highlighting the feasibility of large‐scale restoration. Successful restoration of seagrass habitats requires an understanding of the most appropriate techniques to use for the target species and local conditions of restoration sites, however, there are currently limited studies on Zostera muelleri. Here, we conduct field trials to explore the use of seed‐ and shoot‐based restoration approaches for Z. muelleri in Victoria, Australia. We assessed the feasibility of collecting and germinating seeds in the field for restoration purposes and trialed the success of four shoot‐based transplanting techniques. We found that seed collections for Z. muelleri were highly successful and scalable, with seed collection rates improving from 489 to 1,939 seeds/hour over 2 years. In addition, in situ seedling germination increased from a maximum of 10.80–25.25% over 2 years. In contrast, shoot‐based restoration approaches were more variable, with plants transplanted with their sediment‐intact outperforming all bare‐rooted approaches. Shoot‐based transplanting approaches appear to have more limited application, but may be appropriate for some restoration sites, or used in combination with seeds to achieve the best restoration outcome. Seed‐based approaches have the potential to be viable and scalable for Z. muelleri given that large numbers of seeds can be collected and stored for at least 7 months before successfully germinating in the field. However, further studies are required to overcome the seedling survival bottleneck (approximately 4 months from emergence) and further increase in situ germination rates.

Seagrass restoration requires information on a range of factors including site environmental conditions, appropriate planting techniques, and the identification of sites most likely to support seagrass. To address the question of where to focus restoration efforts, a key first step is to identify trends in the spatio‐temporal distribution of seagrasses to identify areas of persistence, loss, and recent gains. Areas of recent recovery (and adjacent areas), can then be targeted by practitioners for assisted recovery and restoration, whilst areas of persistent loss can be avoided. Here we identified the contemporary distribution, density, and species composition of seagrass ecosystems (using Sentinel 2 imagery and supervised object‐based imagery analysis) and integrated these data with historic extents to identify spatio‐temporal trends in seagrass distribution in Western Port, Victoria, Australia. Contemporary classifications demonstrated acceptable accuracies (Overall Accuracy 0.77–0.85, User Accuracy 0.76–0.97) and predicted a contemporary seagrass extent of 222 km2; with 48 km2 of low‐density recovery predicted to have occurred since 1999. Comparisons with historical seagrass extents indicated some seagrass recovery since large‐scale losses in 1983, although some areas of loss were also present. Recovery included a net gain of approximately 95 km2 in the past 20 years and an eastward range expansion; suggesting environmental conditions have improved and are now conducive for restoration efforts in some areas. Results demonstrate that accurate, low‐cost, remote sensing of seagrass ecosystems is possible and show how understanding spatio‐temporal trends can guide the spatial allocation of resources by prioritizing areas for restoration where recovery is beginning to occur.