Because mangroves store greater amounts of carbon (C) per area than any other terrestrial ecosystem, conservation of mangrove forests on a global scale represents a potentially meaningful strategy for mitigating atmospheric greenhouse‐gas (GHG) emissions. However, analyses of how coastal ecosystems influence the global C cycle also require the mapping of ecosystem area across the Earth's surface to estimate C storage and flux (movement) in order to compare how different ecosystem types may mitigate GHG enrichment in the atmosphere. In this paper, we propose a new framework based on diverse coastal morphology (that is, different coastal environmental settings resulting from how rivers, tides, waves, and climate have shaped coastal landforms) to explain global variations in mangrove C storage, using soil organic carbon (SOC) as a model to more accurately determine mangrove contributions to global C dynamics. We present, to the best of our knowledge, the first global mangrove area estimate occupying distinct coastal environmental settings, comparing the role of terrigenous and carbonate settings as global “blue carbon” hotspots. C storage in deltaic settings has been overestimated, while SOC stocks in carbonate settings have been underestimated by up to 50%. We encourage the scientific community, which has largely focused on blue carbon estimates, to incorporate coastal environmental settings into their evaluations of C stocks, to obtain more robust estimates of global C stocks.
Blue carbon policy supports carbon sequestration whilst also conserving our remaining seagrass meadows. The complex biogeochemical processes within the sediment of seagrass meadows are responsible for the longevity of the stored carbon. Carbon stock and accumulation rates are controlled by the interaction of hydrodynamic, geochemical and biotic processes unique to each meadow. Carbon content (stock and flux) of a meadow must be quantified for inclusion in carbon accounting, whether for market trading or national greenhouse gas accounting. Management of seagrass blue carbon also requires estimates of additionality, leakage, permanence, conversion and emission factors.
Highly productive coastal wetlands play an essential role in storing blue carbon as one of their ecosystem services, but they are increasingly jeopardized by intensive reclamation activities to facilitate rapid population growth and urbanization. Coastal reclamation causes the destruction and severe degradation of wetland ecosystems, which may affect their abilities to store blue carbon. To assist with international accords on blue carbon, we evaluated the dynamics of blue carbon storage in coastal wetlands under coastal reclamation in China. By integrating carbon density data collected from field measurement experiments and from the literature, an InVEST model, Carbon Storage and Sequestration was used to estimate carbon storage across the reclamation area between 1990 and 2015. The result is the first map capable of informing about blue carbon storage in coastal reclamation areas on a national scale. We found that more than 380,000 hectares of coastal wetlands were affected by reclamation, which resulted in the release of ca. 20.7 Tg of blue carbon. The carbon loss from natural wetlands to artificial wetlands accounted for 72.5% of total carbon loss, which highlights the major task in managing coastal sustainability. In addition, the top 20% of coastal wetlands in carbon storage loss covered 4.2% of the total reclamation area, which can be applied as critical information for coastal redline planning. We conclude that the release of blue carbon due to the conversion of natural wetlands exceeded the total carbon emission from energy consumption within the reclamation area. Implementing the Redline policy could guide the management of coastal areas resulting in greater resiliency regarding carbon emission and sustained ecosystem services.
The human-mediated introduction of marine non-indigenous species is a centuries- if not millennia-old phenomenon, but was only recently acknowledged as a potent driver of change in the sea. We provide a synopsis of key historical milestones for marine bioinvasions, including timelines of (a) discovery and understanding of the invasion process, focusing on transfer mechanisms and outcomes, (b) methodologies used for detection and monitoring, (c) approaches to ecological impacts research, and (d) management and policy responses. Early (until the mid-1900s) marine bioinvasions were given little attention, and in a number of cases actively and routinely facilitated. Beginning in the second half of the 20th century, several conspicuous non-indigenous species outbreaks with strong environmental, economic, and public health impacts raised widespread concerns and initiated shifts in public and scientific perceptions. These high-profile invasions led to policy documents and strategies to reduce the introduction and spread of non-indigenous species, although with significant time lags and limited success and focused on only a subset of transfer mechanisms. Integrated, multi-vector management within an ecosystem-based marine management context is urgently needed to address the complex interactions of natural and human pressures that drive invasions in marine ecosystems.
Seagrasses form one of the most ecologically important and productive three-dimensional habitats in coastal seas. Knowing the global distribution of seagrass meadows is essential for conservation and blue carbon estimates. Here, we modelled the global distribution of seagrass using 43,037 occurrence records and 13 environmental variables within the modelling software MaxEnt at 30 arc sec resolution (c. 1 km at the equator). We found that sea surface temperature and distance from land contributed most in predicting seagrass distribution globally. Comparison of summing models for individual species, genera, and families found that a model combining all species occurrence records best fitted the known geographic distribution. In addition, this model fills geographic gaps in previous maps. We predicted the seagrass biome may occupy 1,646,788 km2, more than double previous global estimates. Applications for this dataset include blue carbon estimates, spatial planning such as for designing Marine Protected Areas, environmental sensitivity mapping, and monitoring of change in biome cover.
There are growing calls for the articulation and consideration of different value systems and emotions in shaping conservation and natural resource management decisions and participatory resource governance. This requires recognition of the socio-cultural relations attached to landscape and seascape in marine conservation policy. Taking into account the relationship between the socio-natural environment and socio-political institutions and processes complicates conservation. Making human values and assumptions explicit within the conservation discourse reveals the inadequacy of conservation that is focused on a biodiversity that is framed only as other-than-human nature. This paper considers how the perceived separation between nature and culture underpinning conservation policy and practice exacerbated a conflict between members of a small Scottish island community and the Scottish Government around the creation of a marine protected area (MPA) off the coast of the island. A rich maritime heritage and a distinctive way of knowing the sea suggested the presence of embedded values that appeared to be colliding with values driving the MPA designation process. Social, historical and cultural forces have shaped the perceptions of landscape and seascape of many of the islanders and can help to explain the local resistance to the MPA. Visual participatory methods were used to explore local understandings of the meaning of conservation. The case-study offers insights into different ways in which marine spaces are conceptualised and how this relates to marine resource governance. It contributes to a more complete understanding of human relations with the marine environment in the context of a marine conservation conflict.
The development of the Marine Renewable Energy (MRE) industry is part of the EC Blue Growth Strategy. It brings together a range of relationships across people, sea, and energy, from developers to local communities and policymakers. This calls for diverse approaches, moving beyond an oppositional mindset to one that can establish an inclusive community around MRE development. Ownership of the marine environment is a legal issue, but MRE devices operate within a cultural and emotional sense of place. Early, sustained community engagement and advocacy is crucial to developing an industry whose impacts are likely to be felt before its social benefits materialise. Crucially, local communities could be supported by Social Sciences and Humanities (SSH) research in creating new mythologies and imaginaries through which MRE technologies become an integral part of their culture, as well as part of their biophysical environment. A complex physical, political, and legal environment provides the context for these new marine energy technologies, and its development provides opportunities for SSH research to address issues around the sea and to integrate into the design of new marine energy seascapes.
Citizen Science (CS) strengthens the relationship between society and science through education and engagement, with win-win benefits. Marine Citizen Science (MCS) is increasingly popular, thanks to society’s growing interest in marine environments and marine issues. Scuba diving significantly increases the potential of MCS, thanks to the skills and behavioural properties of people who participate in the sport. To be able to exploit this potential, however, MCS needs to face challenges related to CS, to scuba diving activities and to the broader scuba diving industry. In particular, engagement and recruitment of potential volunteers, as well as retention of active participants, represent key milestones. In order to reach these milestones, information is required on current participation levels of scuba divers in MCS, as well as the motivations behind participation, and the opinions held by potential participants in MCS. This study explored different case studies and methods of data collection to provide an overview of actual and potential participation in MCS by the scuba diving community. The results show that scuba divers, whether active or potential marine citizen scientists, are well disposed towards MCS. Some barriers, however, prevent the full participation of scuba divers as marine citizen scientists. Certain barriers extend beyond the control of both divers and MCS projects, while others, such as limited access to MCS projects and poor feedback after participation, can and should be addressed. The recommendations of this research provide strategic direction to MCS, so that the broad scuba diving community can be successfully integrated into MCS. These recommendations acknowledge the important role played by stakeholders in the scuba diving industry, as well as professional intermediaries and hired experts.
Highly connected networks generally improve resilience in complex systems. We present a novel application of this paradigm and investigated the potential for anthropogenic structures in the ocean to enhance connectivity of a protected species threatened by human pressures and climate change. Biophysical dispersal models of a protected coral species simulated potential connectivity between oil and gas installations across the North Sea but also metapopulation outcomes for naturally occurring corals downstream. Network analyses illustrated how just a single generation of virtual larvae released from these installations could create a highly connected anthropogenic system, with larvae becoming competent to settle over a range of natural deep-sea, shelf and fjord coral ecosystems including a marine protected area. These results provide the first study showing that a system of anthropogenic structures can have international conservation significance by creating ecologically connected networks and by acting as stepping stones for cross-border interconnection to natural populations.
General governance frameworks and ecological models need to be complemented with concrete working processes to efficiently mitigate environmental problems caused by a large number of actors in society. This article, which focuses on marine environmental problems, presents a procedure in which relevant flows of goods and substances in society are linked to the behavior and activities of actors. The exploration of actors is more comprehensive than in currently used procedures which may expand the range of intervention options. Market actors that are normally overlooked in life cycle assessments are disclosed and actors primarily working with information flows are also explored. The implementation of the proposed procedure is strengthened by systematic use of performance indicators. The concrete examples in the present article refer to nutrient inputs into the sea. Management of marine litter and drug residues are two other areas in which a systematic exploration of substance flows and influential actors is likely to be fruitful.
Mass coral bleaching has emerged in the 21st century as the greatest threat to the health of the world's reefs. A sophisticated process understanding of bleaching at the polyp scale has now been achieved through laboratory and field studies, but this knowledge is yet to be applied in mechanistic models of shelf-scale reef systems. In this study we develop a mechanistic model of the coral-symbiont relationship that considers temperature-mediated build-up of reactive oxygen species due to excess light, leading to zooxanthellae expulsion. The model explicitly represents the coral host biomass, as well as zooxanthellae biomass, intracellular pigment concentration, nutrient status, and the state of reaction centres and the xanthophyll cycle. Photophysiological processes represented include photoadaptation, xanthophyll cycle dynamics, and reaction centre state transitions. The mechanistic model of the coral-symbiont relationship is incorporated into a ∼1 km resolution coupled hydrodynamic – biogeochemical model that encompasses the entire ∼2000 km length of the Great Barrier Reef. A simulation of the 2016 bleaching event shows the model is able to capture the broadscale features of the observed bleaching, but fails to capture bleaching on offshore reefs due to the model's grid being unable to resolve the bathymetry of shallow platforms surrounded by deep water. To further analyse the model behaviour, a ∼200 m resolution nested simulation of Davies Reef (18°49′ S, 147°38′ E) is undertaken. We use this nested model to demonstrate the depth gradient in zooxanthellae response to thermal stress. Finally, we discuss the uncertainties in the bleaching model, which lie primarily in quantifying the link between reactive oxygen build-up and the expulsion process. Through the mechanistic representation of environmental forcing, this model of coral bleaching applied in realistic environmental conditions has the potential to generate more detailed predictions than the presently-available satellite-based coral bleaching metrics, and can be used to evaluate proposed management strategies.
Pristine coral reefs possess a tremendous potential for contributing to tourism and economic development. This is especially important for Fiji given their tourism economy's reliance on diving and coastal activities. Understanding divers’ perceptions of coral reefs and environmental issues is, therefore, paramount to sustaining the tourism industry. Despite the importance of coral reefs to the Fijian tourism sector, the Fijian Government has granted exploration licenses to mining companies to assess the viability of deep sea mining (DSM) activities in Fiji's seas. There is concern that DSM may negatively impact reef-related tourism due to tourists’ perception that DSM activities degrades Fiji's coral reefs. This study conducts a contingent behaviour survey to explore how tourists’ expectations of DSM will affect their future travel decisions and subsequently influence overall tourism demand in Fiji. Our findings show that divers and snorkelers demonstrate a high willingness to return to Fiji in the future, based on their previous travel experience, but that they would significantly reduce their future visits if DSM was to take place in Fiji. These results contribute to our understanding of the potential trade-offs between DSM and reef-related tourism and give some preliminary estimates of the potential economic consequences of the Fijian Government allowing DSM within their territorial waters.
Because of demographic and tourism increase, coastal areas are facing higher numbers of recreational users. Together with other factors (environmental quality, protection status), the level of use affects the spatial distribution of users. This level also affects the quality of user experience, because beyond a certain level, the number of users results in decreased user satisfaction; this is the social carrying capacity (SCC), which depends on user and site characteristics. This study assessed the SCC in a popular coastal area and examined how it influences the spatial distribution of users. Boat and visitor counts as well as data from a questionnaire-based survey were analyzed to assess i) crowding perception, ii) factors affecting the disturbance associated with use level, and iii) user's coping strategies when managing high use levels. The results demonstrated that crowding perception and disturbances associated with use level depend on-site characteristics, use level, and user characteristics. Boat type was the main factor affecting user's coping strategy. SCC significantly differed between sites and according to the use level anticipated by users. The SCC was fulfilled at every site within the marine protected areas, except for the sites experiencing the lowest use level. This study provides novel and valuable information for the field of recreational use management, when attempting to achieve either sustainable use goals through SCC assessment or biodiversity conservation goals through the effect of SCC on the spatial distribution of pressures related to recreational uses.
Predation is a critical ecological process that alters the structure and functioning of ecosystems through density-mediated and trait-mediated effects on lower trophic levels. Although studies have focused on harvest-driven reductions in abundances and sizes of targeted species, human harvest also alters species morphologies, life histories, and behaviors by selection, plasticity, and shifts in species interactions. Restricting harvest can recover the biomass of targeted species, but it is less clear how behavioral phenotypes recover, particularly relative to the impacts of potentially opposing pathways of human influence. We investigated the effects of protection on the behavioral traits of a marine fish assemblage, recording behavior of 1377 individual fishes of nine targeted kelp forest species across 16 California marine protected areas (MPAs) varying in age, protection level, and diver visitation. With long-term, full protection from harvest, all fish species exhibited shorter flight initiation distance (FID, or the distance at which an animal flees from an approaching threat) and longer time delays before fleeing, despite differences in trophic position, microhabitat use, and other ecological characteristics. These escape behaviors were amplified across new MPAs regardless of protection level, suggesting that recovery is slow and likely the result of differences in genetic or early-life experience among individuals in these long-lived species. Although the effects of full protection from harvest were partially offset by recovering populations of large piscivorous predators, the net effect of long-term, full protection on fish behavior was shorter FID. Additionally, all species had shorter FID at sites more frequently visited by divers, and this effect was greater in sites with long-term, full protection from fishing. To the extent that escape behavior is correlated with foraging behavior and predation rates, these results suggest that human-induced behavioral changes may affect ecosystem processes, even after abundances have recovered. If recovery of ecosystem functioning and services are the management goal, assessments should be broadened to include the recovery of functional traits (including behavior).
Maintaining the current state of ecosystem services from freshwater and marine ecosystems around the world is at risk. Cumulative effects of multiple human pressures on ecosystem components and functions are indicative of residual pressures that “fall through” the cracks of current industry sector management practices. Without an understanding of the level of residual pressures generated by these measures, we are unlikely to reconcile the root causes of ecosystem effects to improve these management practices to reduce their residual pressures. In this paper, we present a new modelling framework that combines a qualitative and quantitative assessments of the effectiveness of the measures used in the daily operations of industry sectors to predict their residual pressure that is delivered to the ecosystem. The predicted residual pressure can subsequently be used as an input variable for ecosystem models. We combine the Bow-tie analysis of the measures with a Bayesian belief network to quantify the effectiveness of the measures and predict the residual pressures.
Submarine power cables (SPC) have been in use since the mid-19th century, but environmental concerns about them are much more recent. With the development of marine renewable energy technologies, it is vital to understand their potential impacts. The commissioning of SPC may temporarily or permanently impact the marine environment through habitat damage or loss, noise, chemical pollution, heat and electromagnetic field emissions, risk of entanglement, introduction of artificial substrates, and the creation of reserve effects. While growing numbers of scientific publications focus on impacts of the marine energy harnessing devices, data on impacts of associated power connections such as SPC are scarce and knowledge gaps persist. The present study (1) examines the different categories of potential ecological effects of SPC during installation, operation and decommissioning phases and hierarchizes these types of interactions according to their ecological relevance and existing scientific knowledge, (2) identifies the main knowledge gaps and needs for research, and (3) sets recommendations for better monitoring and mitigation of the most significant impacts. Overall, ecological impacts associated with SPC can be considered weak or moderate, although many uncertainties remain, particularly concerning electromagnetic effects.
This paper deals with fishery management in the face of the ecological and economic effects of global warming. To achieve this, a dynamic bioeconomic model and model-based scenarios are considered, in which the stock's growth function depends on the sea surface temperature. The model is empirically calibrated for the French Guiana shrimp fishery using time series collected over the period 1993–2009. Three fishing effort strategies are then compared under two contrasted IPCC climate scenarios (RCP 8.5 and RCP 2.6). A first harvesting strategy maintains the Status Quo in terms of fishing effort. A more ecologically-oriented strategy based on the closure of the fishery is also considered. A third strategy, which relates to Maximum Economic Yield (MEY), is based on the optimisation of the net present value derived from fishing. The results first show that ‘Status Quo’ fishing intensity combined with global warming leads to the collapse of the fishery in the long run. Secondly, it turns out that the Closure strategy preserves stock viability especially under the optimistic climate scenario. Thirdly, the MEY strategy makes it possible to satisfy bioeconomic performances requirements with positive stock and profit, once again, especially under the optimistic warming scenario. Consequently, MEY emerges as a relevant bioeconomic strategy in terms of adaptation to climate change but only in connection with climate change mitigation.
Some species may be more important in transferring the complex effects of multiple human stressors through marine food‐webs. Here we show a novel approach to help inform conservation management in identifying such species. Simulating changes in biomass between species from the interaction effects of ocean warming and ocean acidification, and fisheries to year 2050 on the south‐eastern Australian marine system, we constructed annual interaction effect networks (IEN's). Each IEN was composed of the species linked by either an additive (sum of the individual stressor response), synergistic (lower biomass compared with additive effects) or antagonistic (greater biomass compared with additive effects) response. Structurally, over the simulation period, the number of species and links in the synergistic IEN's increased and the network structure became more stable. The stability of the antagonistic IEN's decreased and became more vulnerable to the loss of species. In contrast, there was no change in the structural attributes of species linked by an additive response. Using indices of species importance common in food‐web and network theory, we identified the most important species within each IEN for transferring the interaction stressor effect on changes in biomass via local, intermediate and global interaction pathways. Mid trophic level mesopelagic fish species were most often identified as the key species within the synergistic IEN's and phytoplankton or zooplankton within the antagonistic IEN's. For the additive response commonly assumed in conservation management demersal fish species were identified by all of the indices. Apart from identifying the most important species, we also identified other important species for transferring the different interaction effects. Knowing the most important species for transferring synergistic or antagonistic responses may help inform conservation strategies for conserving ecosystems under increasing multiple stressor impacts.
Governing marine environments has evolved from dominant interests in exploitation, allocation, conservation, and protection to restoration. Compared to terrestrial and freshwater environments, restoration of and in marine ecosystems presents a new mode of intervention with both technical and governance challenges. This paper aims to enhance understanding of the important factors at play in governing marine ecosystem restoration. Discourses of marine ecosystem restoration are an important factor which shape how the restoration activity is governed, as discourses structure how actors and coalitions define problems and their approaches to solutions. The article produces a conceptual model of the discourses of marine ecosystem restoration, built on two dimensions: (1) the degree of human intervention and (2) motivations for restoration. Together, these dimensions create four broad restoration discourses: “Putting Nature First,” “Bringing Nature Back,” “Helping Nature support Humans,” and “Building with Nature.” Moreover, marine ecosystem restoration is confronted with different forms of uncertainty, such as incomplete knowledge, unpredictability, and ambiguity, which must be managed by actors participating in restoration initiatives. The article's overall contribution is the synthesis of these components, which illuminates the specific governance challenges under various circumstances.
During the 20th century, many large-bodied fish stocks suffered from unsustainable fishing pressure. Now, signs of recovery are appearing among previously overfished large-bodied fish stocks. This new situation raises the question of whether current fisheries advice and management procedures, which were devised and optimized for depleted stocks, are well-suited for the management of recovered stocks. We highlight two challenges for fisheries advice and management: First, recovered stocks are more likely to show density-dependent growth. We show how the appearance of density-dependent growth will make reference points calculated with current procedures inaccurate. Optimal exploitation of recovered large-bodied fish stocks will therefore require accounting for density-dependent growth. Second, we show how a biomass increase of large-bodied piscivorous fish will lead to a reverse trophic cascade, where their increased predation mortality on forage fish reduces forage fish productivity and abundance. The resulting decrease in maximum sustainable yield of forage fish stocks could lead to conflicts between forage and large-piscivore fisheries. Avoiding such conflicts requires that choices are made between the exploitation of interacting fish stocks. Failure to account for the changed ecological state of recovered stocks risks creating new obstacles to sustainable fisheries management.