The rapid expansion of human activities threatens ocean-wide biodiversity. Numerous marine animal populations have declined, yet it remains unclear whether these trends are symptomatic of a chronic accumulation of global marine extinction risk. We present the first systematic analysis of threat for a globally distributed lineage of 1,041 chondrichthyan fishes—sharks, rays, and chimaeras. We estimate that one-quarter are threatened according to IUCN Red List criteria due to overfishing (targeted and incidental). Large-bodied, shallow-water species are at greatest risk and five out of the seven most threatened families are rays. Overall chondrichthyan extinction risk is substantially higher than for most other vertebrates, and only one-third of species are considered safe. Population depletion has occurred throughout the world's ice-free waters, but is particularly prevalent in the Indo-Pacific Biodiversity Triangle and Mediterranean Sea. Improved management of fisheries and trade is urgently needed to avoid extinctions and promote population recovery.

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Extinction risk and conservation of the world's sharks and rays

Antarctic krill Euphausia superba (hereafter `krill') occur in regions undergoing rapid environmental change, particularly loss of winter sea ice. During recent years, harvesting of krill has in creased, possibly enhancing stress on krill and Antarctic ecosystems. Here we review the overall impact of climate change on krill and Antarctic ecosystems, discuss implications for an ecosystem-based fisheries management approach and identify critical knowledge gaps. Sea ice decline, ocean warming and other environmental stressors act in concert to modify the abundance, distribution and life cycle of krill. Although some of these changes can have positive effects on krill, their cumulative impact is most likely negative. Recruitment, driven largely by the winter survival of larval krill, is probably the population parameter most susceptible to climate change. Predicting changes to krill populations is urgent, because they will seriously impact Antarctic ecosystems. Such predictions, however, are complicated by an intense inter-annual variability in recruitment success and krill abundance. To improve the responsiveness of the ecosystem-based management approach adopted by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), critical knowledge gaps need to be filled. In addition to a better understanding of the factors influencing recruitment, management will require a better understanding of the resilience and the genetic plasticity of krill life stages, and a quantitative understanding of under-ice and benthic habitat use. Current precautionary management measures of CCAMLR should be maintained until a better understanding of these processes has been achieved. [GRAPHICS] .

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Impact of climate change on Antarctic krill

Since the early 1970s a considerable number of multilateral agreements have been concluded in the environmental field that establish a common pattern of institutional arrangements. The purpose of these arrangements is to develop the normative content of the regulatory regime established by each agreement1 and to supervise the states parties’ implementation of and compliance with that regime. These institutional arrangements usually comprise a conference or meeting of the parties (COP, MOP) with decision-making powers, a secretariat, and one or more specialist subsidiary bodies. Such arrangements, because of their ad hoc nature, are not intergovernmental organizations (IGOs) in the traditional sense. On the other hand, as the creatures of treaties, such conferences and meetings of the parties, with their secretariats and subsidiary bodies, add up to more than just diplomatic conferences. Because such arrangements do not constitute traditional IGOs and yet are freestanding and distinct both from the states parties to a particular agreement and from existing IGOs, we have chosen to describe them as “autonomous.” They are also autonomous in the sense that they have their own lawmaking powers and compliance mechanisms.

Autonomous institutional arrangements in multilateral environmental agreements: a little-noticed phenomenon in international law

Antarctica is the most isolated continent on Earth, but it has not escaped the negative impacts of human activity. The unique marine ecosystems of Antarctica and their endemic faunas are affected on local and regional scales by overharvesting, pollution, and the introduction of alien species. Global climate change is also having deleterious impacts: rising sea temperatures and ocean acidification already threaten benthic and pelagic food webs. The Antarctic Treaty System can address local- to regional-scale impacts, but it does not have purview over the global problems that impinge on Antarctica, such as emissions of greenhouse gases. Failure to address human impacts simultaneously at all scales will lead to the degradation of Antarctic marine ecosystems and the homogenization of their composition, structure, and processes with marine ecosystems elsewhere.

Anthropogenic impacts on marine ecosystems in Antarctica.

Cumulative human impacts across the world's oceans are considerable. We therefore examined a single model taxonomic group, the penguins (Spheniscidae), to explore how marine species and communities might be at risk of decline or extinction in the southern hemisphere. We sought to determine the most important threats to penguins and to suggest means to mitigate these threats. Our review has relevance to other taxonomic groups in the southern hemisphere and in northern latitudes, where human impacts are greater. Our review was based on an expert assessment and literature review of all 18 penguin species; 49 scientists contributed to the process. For each penguin species, we considered their range and distribution, population trends, and main anthropogenic threats over the past approximately 250 years. These threats were harvesting adults for oil, skin, and feathers and as bait for crab and rock lobster fisheries; harvesting of eggs; terrestrial habitat degradation; marine pollution; fisheries bycatch and resource competition; environmental variability and climate change; and toxic algal poisoning and disease. Habitat loss, pollution, and fishing, all factors humans can readily mitigate, remain the primary threats for penguin species. Their future resilience to further climate change impacts will almost certainly depend on addressing current threats to existing habitat degradation on land and at sea. We suggest protection of breeding habitat, linked to the designation of appropriately scaled marine reserves, including in the High Seas, will be critical for the future conservation of penguins. However, large-scale conservation zones are not always practical or politically feasible and other ecosystem-based management methods that include spatial zoning, bycatch mitigation, and robust harvest control must be developed to maintain marine biodiversity and ensure that ecosystem functioning is maintained across a variety of scales.

Pollution, habitat loss, fishing, and climate change as critical threats to penguins.

The fauna‐rich Southern Ocean provides the background for a conflict of national interests of an economic, legal, political, scientific, and conservationist nature. In an attempt to resolve what may well prove to be a collection of insuperable conflicts, the nations overseeing the Antarctic region negotiated and signed the Convention on the Conservation of Antarctic Marine Living Resources in 1980. This Convention purports to regulate national involvement in the Southern Ocean by managing the exploitation of all life in the nearly pristine Antarctic marine ecosystem. Krill and various species of fish have been harvested in the Southern Ocean for more than a decade, but at levels far below those that nearly led to the extinction of Antarctic whales and seals. The promise of this conservation Convention is to allow a stable level of harvesting of all species for the foreseeable future. If ratified, the Convention would create a supervisory Conservation Commission and an advisory Scientific Committe...

Ronald F. Frank

Papers

Convention on the conservation of antarctic marine living resources