Assessing different causes of crown-of-thorns starfish outbreaks and appropriate responses for management on the Great Barrier Reef

The crown-of-thorns starfish Acanthaster planci (COTS) has contributed greatly to declines in coral cover on Australia's Great Barrier Reef, and remains one of the major acute disturbances on Indo-Pacific coral reefs. Despite uncertainty about the underlying causes of outbreaks and the management responses that might address them, few studies have critically and directly compared competing hypotheses. This study uses qualitative modelling to compare hypotheses relating to outbreak initiation, explicitly considering the potential role of positive feedbacks, elevated nutrients, and removal of starfish predators by fishing. When nutrients and fishing are considered in isolation, the models indicate that a range of alternative hypotheses are capable of explaining outbreak initiation with similar levels of certainty. The models also suggest that outbreaks may be caused by multiple factors operating simultaneously, rather than by single proximal causes. As the complexity and realism of the models increased, the certainty of outcomes decreased, but key areas that require further research to improve the structure of the models were identified. Nutrient additions were likely to result in outbreaks only when COTS larvae alone benefitted from nutrients. Similarly, the effects of fishing on the decline of corals depended on the complexity of interactions among several categories of fishes. Our work suggests that management approaches which seek to be robust to model structure uncertainty should allow for multiple potential causes of outbreaks. Monitoring programs can provide tests of alternative potential causes of outbreaks if they specifically monitor all key taxa at reefs that are exposed to appropriate combinations of potential causal factors

Ocean warming alters species abundance patterns and increases species diversity in an African sub-tropical reef-fish community

The impacts of ocean warming resulting from recent climate change on the abundance patterns of marine species have been well documented in temperate seas of the northern hemisphere, but the impacts of a widening tropical belt are largely unexplored. Using measurements of sea surface temperature and spear-fishing records for 84 species spanning a 19-yr period, we examined the effects of ocean warming on a sub-tropical reef-fish community on the southeastern coast of Africa. Corresponding with a 0.46°C increase in average sea surface temperature between the time periods 1989–97 and 2002–2007, the ratio of species showing an overall decrease/ no change/increase in abundance was 1 : 3 : 2 among six species at the northern limits of their distribution in the region (temperate species), 1 : 15 : 6 among 22 broadly distributed species, and 1 : 5 : 9 among 15 species at the southern limits of their distribution (tropical species). Also, the relative abundance of temperate species as a whole decreased by 10–13% whereas that of tropical species increased by 9%, and broadly distributed species showed little change. Average species richness and diversity increased 33 and 15% respectively between the two time periods. These results are broadly consistent with a predicted poleward shift in species ranges and a predicted increase in species richness and diversity with increasing sea temperature. Our findings confirm that large-scale climate change causing a widening of the tropical belt and subsequent ocean warming is having a profound impact on marine species abundance patterns and community composition at a local scale in the sub-tropics

Modelling marine protected areas: insights and hurdles

Models provide useful insights into conservation and resource management issues and solutions. Their use to date has highlighted conditions under which no-take marine protected areas (MPAs) may help us to achieve the goals of ecosystem-based management by reducing pressures, and where they might fail to achieve desired goals. For example, static reserve designs are unlikely to achieve desired objectives when applied to mobile species or when compromised by climate-related ecosystem restructuring and range shifts. Modelling tools allow planners to explore a range of options, such as basing MPAs on the presence of dynamic oceanic features, and to evaluate the potential future impacts of alternative interventions compared with 'no-action' counterfactuals, under a range of environmental and development scenarios. The modelling environment allows the analyst to test if indicators and management strategies are robust to uncertainties in how the ecosystem (and the broader human-ecosystem combination) operates, including the direct and indirect ecological effects of protection. Moreover, modelling results can be presented at multiple spatial and temporal scales, and relative to ecological, economic and social objectives. This helps to reveal potential 'surprises', such as regime shifts, trophic cascades and bottlenecks in human responses. Using illustrative examples, this paper briefly covers the history of the use of simulation models for evaluating MPA options, and discusses their utility and limitations for informing protected area management in the marine realm

Quantitative Foresighting as a Means of Improving Anticipatory Scientific Capacity and Strategic Planning

In a rapidly changing world, scientists and research institutions need to plan for the infrastructure, skills, and policy engagement that will help society navigate social-ecological challenges. Foresighting draws on approaches used in strategic and long-range (>10 years) planning and participatory futures studies. Here, we describe a new quantitative approach to develop and rank 14 foresight scenarios across a range of general and marine-relevant science domains. Indicators for each foresight were used to assess the time-specific probability of each scenario being realized. Assessments by scientists in 2 consecutive years showed foresight scoring consistency and revealed surprises. Despite high variation among scientists in scoring the year that each indicator would occur, there was overall consistency across the foresights between years. We show that foresighting can be quantitative and that individual performance and changes in likelihood can be evaluated. This approach can motivate and guide strategic planning and investment decisions by scientific institutions in response to different anticipated futures and build skills in futures thinking

Integrating management of marine activities in Australia

Integrated management (IM) has been widely proposed, but difficult to achieve in practice, and there remains the need for evaluation of examples that illustrate the practical issues that contribute to IM success or failure. This paper synthesises experiences of academics and practitioners involved in seven Australian case studies in which there have been attempts to integrate or take a broader, holistic perspective of management. The evaluative framework of Stephenson et al. (2019a) was used as a lens to explore, through workshops and a questionnaire survey, the nine key features and five anticipated stages of IM in the Gladstone Harbour Project, the Great Barrier Reef, the Northern Prawn fishery and regional development, the South-East Queensland Healthy Waterways Partnership, the Australian Oceans Policy, the New South Wales Marine Estate reforms, and progress toward Integrated Management in the Spencer Gulf. Workshops involving experts with direct experience of the case studies revealed that most of the key features (recognition of the need; a shared vision for IM; appropriate legal and policy frameworks; effective process for appropriate stakeholder participation; comprehensive suite of objectives (ecological, social, cultural, economic and institutional); consideration of trade-offs and cumulative effects of multiple activities; flexibility to adapt to changing conditions; process for ongoing review, evaluation and refinement; and effective resourcing) were seen as important in all case studies. However, there are only a few examples where key features of IM were implemented ‘fully’. A subsequent questionnaire of participants using ‘best-worst’ scaling indicated that an appropriate legal and institutional framework is considered to have most influence on IM outcomes, and therefore is the most important of the key features. This is followed in salience by effective stakeholder participation, effective resourcing, capacity and tools, and recognition of the need for IM. Key features may change in relative importance at different stages in the trajectory of IM

Integrated modelling to support decision-making for marine social-ecological systems in Australia

Policy- and decision-makers require assessments of status and trends for marine species, habitats, and ecosystems to understand if human activities in the marine environment are sustainable, particularly in the face of global change. Central to many assessments are statistical and dynamical models of populations, communities, ecosystems, and their socioeconomic systems and management frameworks. The establishment of a national system that could facilitate the development of such model-based assessments has been identified as a priority for addressing management challenges for Australia's marine environment. Given that most assessments require cross-scale information, individual models cannot capture all of the spatial, temporal, biological, and socioeconomic scales that are typically needed. Coupling or integrating models across scales and domains can expand the scope for developing comprehensive and internally consistent, system-level assessments, including higher-level feedbacks in social-ecological systems. In this article, we summarize: (i) integrated modelling for marine systems currently being undertaken in Australia, (ii) methods used for integration and comparison of models, and (iii) improvements to facilitate further integration, particularly with respect to standards and specifications. We consider future needs for integrated modelling of marine social-ecological systems in Australia and provide a set of recommendations for priority focus areas in the development of a national approach to integrated modelling. These recommendations draw on-and have broader relevance for-international efforts around integrated modelling to inform decision-making for marine systems