Avoiding coral reef functional collapse requires local and global action

Coral reefs face multiple anthropogenic threats, from pollution and overfishing to the dual effects of greenhouse gas emissions: rising sea temperature and ocean acidification [1]. While the abundance of coral has declined in recent decades [2 and 3], the implications for humanity are difficult to quantify because they depend on ecosystem function rather than the corals themselves. Most reef functions and ecosystem services are founded on the ability of reefs to maintain their three-dimensional structure through net carbonate accumulation [4]. Coral growth only constitutes part of a reef’s carbonate budget; bioerosion processes are influential in determining the balance between net structural growth and disintegration [5 and 6]. Here, we combine ecological models with carbonate budgets and drive the dynamics of Caribbean reefs with the latest generation of climate models. Budget reconstructions using documented ecological perturbations drive shallow (6–10 m) Caribbean forereefs toward an increasingly fragile carbonate balance. We then projected carbonate budgets toward 2080 and contrasted the benefits of local conservation and global action on climate change. Local management of fisheries (specifically, no-take marine reserves) and the watershed can delay reef loss by at least a decade under “business-as-usual” rises in greenhouse gas emissions. However, local action must be combined with a low-carbon economy to prevent degradation of reef structures and associated ecosystem services.

Colliding stories; how discourses in ocean acidification are subsumed in climate change

Like climate change, ocean acidification is a globally complex problem caused by increasing atmospheric CO2 as a result of human consequences from carbon intensive social practices. Using inductive discourse methods and thematic analysis, this study examines the complex interplay of social ideas using Hajer’s storyline framework as the method of choice to draw comparisons between narrative features in ocean acidification and climate change discourses and identifies whether ocean acidification is characterised together or separately from climate change as a result of new storylines. Any separation may not only benefit ocean acidification but may also alter the current resolution pathway for climate change. Interview research drives emergent narrative themes which are configured using data coding categories. The number of categories is limited partly by design to make it easier to interpret and analyse interview participant viewpoints and their corresponding storylines. Narratives are contextualised into three emergent themes with focus on political, technological and social pathways, with particular focus on storylines that are energised and routinised by participants through social everyday practice.

Assessing the risk of climate change to aquaculture: a case study from south-east Australia

A qualitative screening-level risk assessment was developed to evaluate relative levels of risk from climate change to aquaculture industries. The assessment was applied to 7 major industries in the temperate south-east region of Australia and involved a simple, transparent and repeatable methodology that was appropriate for a range of different aquaculture systems and taxa. Two key stages were involved: the development of comprehensive expertise-based literature reviews or ‘species profiles’ and a scoring assessment, with the latter providing a defined framework within which industries could be ranked (from high to low risk). In addition to informing the second stage of the risk assessment process, the species’ profiles also highlighted important climate change drivers and key information uncertainties and knowledge gaps. There was good resolution among the scoring assessments, with only 2 industries receiving the same risk score. The results indicated that oysters farmed from wild spat (Sydney rock oysters Saccostrea glomerata) were at most risk to climate change, with warm temperate hatchery-based finfish species (yellowtail kingfish Seriola lalandi) being the least at risk. This study provides critical guidance for scientists, resource managers and stakeholders for future research, both in addressing key knowledge gaps and focussing the development of more detailed risk analyses for high risk aquaculture industries in south-east Australia.

Mixed responses of tropical Pacific fisheries and aquaculture to climate change

Pacific Island countries have an extraordinary dependence on fisheries and aquaculture. Maintaining the benefits from the sector is a difficult task, now made more complex by climate change. Here we report how changes to the atmosphere–ocean are likely to affect the food webs, habitats and stocks underpinning fisheries and aquaculture across the region. We found winners and losers—tuna are expected to be more abundant in the east and freshwater aquaculture and fisheries are likely to be more productive. Conversely, coral reef fisheries could decrease by 20% by 2050 and coastal aquaculture may be less efficient. We demonstrate how the economic and social implications can be addressed within the sector—tuna and freshwater aquaculture can help support growing populations as coral reefs, coastal fisheries and mariculture decline.

The economic impacts of ocean acidification on coral reefs

Because ocean acidification has only recently been recognized as a problem caused by CO₂ emissions, impact studies are still rare and estimates of the economic impact are absent. This paper estimates the economic impact of ocean acidification on coral reefs which are generally considered to be economically as well as ecologically important ecosystems. First, we conduct an impact assessment in which atmospheric concentration of CO₂ is linked to ocean acidity causing coral reef area loss. Next, a meta-analytic value transfer is applied to determine the economic value of coral reefs around the world. Finally, these two analyses are combined to estimate the economic impact of ocean acidification on coral reefs for the four IPCC marker scenarios. We find that the annual economic impact rapidly escalates over time, because the scenarios have rapid economic growth in the relevant countries and coral reefs are a luxury good. Nonetheless, the annual value in 2100 in still only a fraction of total income, one order of magnitude smaller than the previously estimated impact of climate change. Although the estimated impact is uncertain, the estimated confidence interval spans one order of magnitude only. Future research should seek to extend the estimates presented here to other impacts of ocean acidification and investigate the implications of our findings for climate policy.

Consistent assessments of pathways toward sustainable development and climate stabilization

Many of the numerous difficult issues facing the world today involve relationships entailing trade-offs and synergies. This study quantitatively assesses some alternative scenarios using integrated assessment models, and provides several indicators relating to sustainable development and climate change, such as indicators of income (per capita GDP), poverty, water stress, food access, sustainable energy use, energy security, and ocean acidification, with high consistencies among the indicators within a scenario. According to the analyses, economic growth helps improve many of the indicators for sustainable development. On the other hand, climate change will induce some severe impacts such as ocean acidification under a non-climate intervention scenario (baseline scenario). Deep emission reductions, such as to 2°C above the pre-industrial level, could cause some sustainable development indicators to worsen. There are complex trade-offs between climate change mitigation levels and several sustainable development indicators. A delicately balanced approach to economic growth will be necessary for sustainable development and responses to climate change.

Predicting interactions among fishing, ocean warming, and ocean acidification in a marine system with whole-ecosystem models

An important challenge for conservation is a quantitative understanding of how multiple human stressors will interact to mitigate or exacerbate global environmental change at a community or ecosystem level. We explored the interaction effects of fishing, ocean warming, and ocean acidification over time on 60 functional groups of species in the southeastern Australian marine ecosystem. We tracked changes in relative biomass within a coupled dynamic whole-ecosystem modeling framework that included the biophysical system, human effects, socioeconomics, and management evaluation. We estimated the individual, additive, and interactive effects on the ecosystem and for five community groups (top predators, fishes, benthic invertebrates, plankton, and primary producers). We calculated the size and direction of interaction effects with an additive null model and interpreted results as synergistic (amplified stress), additive (no additional stress), or antagonistic (reduced stress). Individually, only ocean acidification had a negative effect on total biomass. Fishing and ocean warming and ocean warming with ocean acidification had an additive effect on biomass. Adding fishing to ocean warming and ocean acidification significantly changed the direction and magnitude of the interaction effect to a synergistic response on biomass. The interaction effect depended on the response level examined (ecosystem vs. community). For communities, the size, direction, and type of interaction effect varied depending on the combination of stressors. Top predator and fish biomass had a synergistic response to the interaction of all three stressors, whereas biomass of benthic invertebrates responded antagonistically. With our approach, we were able to identify the regional effects of fishing on the size and direction of the interacting effects of ocean warming and ocean acidification.

Socio-economic impacts of ocean acidification in the Mediterranean Sea

Ocean acidification appears as another environmental pressure associated with anthropogenic emissions of carbon dioxide. This paper aims to assess the likely magnitude of this phenomenon in the Mediterranean region. This involves translating expected changes in ocean chemistry into impacts, first on marine and coastal ecosystems and then, through effects on services provided by these to humans, into socio-economic costs. Economic market and non-market valuation techniques are needed for this purpose. Important sectors affected are tourism and recreation, red coral extraction, and fisheries (both capture and aquaculture production). In addition, the costs associated with the disruption of ecosystem regulating services, notably carbon sequestration and non-use values will be considered. Finally, indirect impacts on other economic sectors will have to be estimated. The paper discusses the framework and methods to accomplish all of this, and offers a preliminary, qualitative overall assessment.

Impact of climate change in Mediterranean aquaculture

The Mediterranean Sea is the biggest marginal sea of the Earth and is at the centre of the life for several millions of people. Seafood is consumed widely in this region, with an average of 16.5 kg/capita/year, and one-fourth of the seafood supply comes from aquaculture activities. The Mediterranean aquaculture sector has expanded in recent decades. Production increased by 77% over the past decade reaching about 1.3 million metric tonnes in 2009. The total value of production was around 3700 million US dollars, representing 3.4% of the value of global aquaculture production. The growth of seafood demand in the Mediterranean is expected to increase in the future, especially in southern countries. Yet, during the 21st century, the Mediterranean basin is expected to observe: (i) an increase in air temperature of between 2.2°C and 5.1°C; (ii) a decrease in rainfall of between 4% and 27%; (iii) an increase in drought periods related to a high frequency of days during which the temperature would exceed 30°C; and (iv) an increase of the sea level of around 35 cm and saline intrusion. Moreover, extreme events, such as heat waves, droughts or floods, are likely to be more frequent and violent. This paper reviews the present status of Mediterranean aquaculture (e.g. production trends, main farmed species, production systems, major producing countries), the most relevant impacts of climate change on this sector (temperature, eutrophication, harmful algae blooms, water stress, sea level rise, acidification and diseases) and proposes a wide range of adaptation and mitigation strategies that might be implemented to minimize impacts.

Ocean sustainability as an inward journey

Society is currently facing interrelated threats to the environment, human health and wellbeing. At the present time, human activity is degrading the health of the ocean, and currently utilized marine resource management approaches are seen to be failures. It is well known that what a society utilizes as a food source is indicative of that society’s ecologic role in the bio-system. A literature survey, from both an environmental and health based perspective, of human interactions with marine based foods was undertaken with emphasis being given to past, current, and future uses for marine based foods, in particular macroalgae. It is speculated that a successful marine resource management approach will require interdisciplinary awareness and knowledge defragmentation by social and scientific researchers, as well as broad based societal behavior changes and acceptance of those changes by a majority of individuals. This behavioral shift will likely require a majority of societal members to turn inwardly through the lens of nature, in particular to the ocean as a food source in order to see a sustainable way forward. In conclusion, several hallmarks of what a successful marine resource management approach would look like from a practical societal standpoint are considered.