Posts Tagged 'fishing pressure'

Effects of near-future ocean acidification, fishing, and marine protection on a temperate coastal ecosystem

Understanding ecosystem responses to global and local anthropogenic impacts is paramount to predicting future ecosystem states. We used an ecosystem modeling approach to investigate the independent and cumulative effects of fishing, marine protection, and ocean acidification on a coastal ecosystem. To quantify the effects of ocean acidification at the ecosystem level, we used information from the peer-reviewed literature on the effects of ocean acidification. Using an Ecopath with Ecosim ecosystem model for the Wellington south coast, including the Taputeranga Marine Reserve (MR), New Zealand, we predicted ecosystem responses under 4 scenarios: ocean acidification + fishing; ocean acidification + MR (no fishing); no ocean acidification + fishing; no ocean acidification + MR for the year 2050. Fishing had a larger effect on trophic group biomasses and trophic structure than ocean acidification, whereas the effects of ocean acidification were only large in the absence of fishing. Mortality by fishing had large, negative effects on trophic group biomasses. These effects were similar regardless of the presence of ocean acidification. Ocean acidification was predicted to indirectly benefit certain species in the MR scenario. This was because lobster (Jasus edwardsii) only recovered to 58% of the MR biomass in the ocean acidification + MR scenario, a situation that benefited the trophic groups lobsters prey on. Most trophic groups responded antagonistically to the interactive effects of ocean acidification and marine protection (46%; reduced response); however, many groups responded synergistically (33%; amplified response). Conservation and fisheries management strategies need to account for the reduced recovery potential of some exploited species under ocean acidification, nonadditive interactions of multiple factors, and indirect responses of species to ocean acidification caused by declines in calcareous predators.

Continue reading ‘Effects of near-future ocean acidification, fishing, and marine protection on a temperate coastal ecosystem’

Operationalizing resilience for adaptive coral reef management under global environmental change

Cumulative pressures from global climate and ocean change combined with multiple regional and local-scale stressors pose fundamental challenges to coral reef managers worldwide. Understanding how cumulative stressors affect coral reef vulnerability is critical for successful reef conservation now and in the future. In this review, we present the case that strategically managing for increased ecological resilience (capacity for stress resistance and recovery) can reduce coral reef vulnerability (risk of net decline) up to a point. Specifically, we propose an operational framework for identifying effective management levers to enhance resilience and support management decisions that reduce reef vulnerability. Building on a system understanding of biological and ecological processes that drive resilience of coral reefs in different environmental and socio-economic settings, we present an Adaptive Resilience-Based management (ARBM) framework and suggest a set of guidelines for how and where resilience can be enhanced via management interventions. We argue that press-type stressors (pollution, sedimentation, overfishing, ocean warming and acidification) are key threats to coral reef resilience by affecting processes underpinning resistance and recovery, while pulse-type (acute) stressors (e.g. storms, bleaching events, crown-of-thorns starfish outbreaks) increase the demand for resilience. We apply the framework to a set of example problems for Caribbean and Indo-Pacific reefs. A combined strategy of active risk reduction and resilience support is needed, informed by key management objectives, knowledge of reef ecosystem processes and consideration of environmental and social drivers. As climate change and ocean acidification erode the resilience and increase the vulnerability of coral reefs globally, successful adaptive management of coral reefs will become increasingly difficult. Given limited resources, on-the-ground solutions are likely to focus increasingly on actions that support resilience at finer spatial scales, and that are tightly linked to ecosystem goods and services.

Continue reading ‘Operationalizing resilience for adaptive coral reef management under global environmental change’

Future-proofing marine protected area networks for cold water coral reefs

Ideally, networks of marine protected areas should be designed with consideration for future changes. We examine how this could be tackled using the example of cold-water coral reefs which provide a number of ecosystem services but are vulnerable to both managed pressures (e.g. deep-water trawling) and unmanaged pressures (e.g. ocean acidification). We collated data on the known and predicted distribution of Northeast Atlantic coral reefs, their protected areas, and fishing effort. We modelled the effects of ocean acidification on aragonite saturation to examine whether existing protected areas will ensure adequate protection for cold-water coral reefs under four possible future scenarios across two models. The best-case scenario suggests only minor impacts of ocean acidification, and that trawling remains the main threat to these reefs. However, in the worst-case scenario, by 2060, over 85% of these reefs are expected to be exposed to corrosive waters. We argue that unmanaged pressures such as ocean acidification and global warming should be incorporated into marine management decisions, with a focus on the protection of cold-water coral reefs to ensure long-term survival of these habitats. A similar approach could be taken for other iconic marine habitats in the face of climate change.

Continue reading ‘Future-proofing marine protected area networks for cold water coral reefs’

Cumulative human impacts on Mediterranean and Black Sea marine ecosystems: assessing current pressures and opportunities

Management of marine ecosystems requires spatial information on current impacts. In several marine regions, including the Mediterranean and Black Sea, legal mandates and agreements to implement ecosystem-based management and spatial plans provide new opportunities to balance uses and protection of marine ecosystems. Analyses of the intensity and distribution of cumulative impacts of human activities directly connected to the ecological goals of these policy efforts are critically needed. Quantification and mapping of the cumulative impact of 22 drivers to 17 marine ecosystems reveals that 20% of the entire basin and 60–99% of the territorial waters of EU member states are heavily impacted, with high human impact occurring in all ecoregions and territorial waters. Less than 1% of these regions are relatively unaffected. This high impact results from multiple drivers, rather than one individual use or stressor, with climatic drivers (increasing temperature and UV, and acidification), demersal fishing, ship traffic, and, in coastal areas, pollution from land accounting for a majority of cumulative impacts. These results show that coordinated management of key areas and activities could significantly improve the condition of these marine ecosystems.

Continue reading ‘Cumulative human impacts on Mediterranean and Black Sea marine ecosystems: assessing current pressures and opportunities’

Managing local coastal stressors to reduce the ecological effects of ocean acidification and warming

Anthropogenic activities have increased the number of stressors acting on ecosystems. When multiple stressors act simultaneously, there is a greater probability of additive, synergistic and antagonistic effects occurring among them. Where additive and synergistic effects occur, managers may yield disproportionately large benefits where they first act upon synergies. Stressors act, however, at different spatial and temporal scales. Global stressors (e.g., ocean acidification and warming) tend to change slowly over long periods of time, although their intensity and effects are contingent on local conditions. On the other hand, local stressors tend to change rapidly over shorter, more defined spatial and temporal scales. Hence, local stressors can be subject to a greater degree of control through local management (e.g., eutrophication and overfishing) while global stressors are characterized by an intrinsic inertia whose effects last for decades, if not centuries. Although the reduction of carbon emissions is an international priority for managing global stressors, it requires international agreements and management applications that take considerable time to develop. Managers, however, may ‘buy time’ by acting on stressors whose governance is local (e.g., reducing nutrient input) and are known to synergize with global stressors (e.g., enriched CO2). Such local actions may potentially disrupt synergies with the more slowly changing global stressors that can only be reduced over longer time scales.

Continue reading ‘Managing local coastal stressors to reduce the ecological effects of ocean acidification and warming’

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Ocean acidification in the IPCC AR5 WG II

OUP book