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Precautionary conservation and cooperative global governance are needed to protect Antarctic blue carbon: the world's largest increasing natural form of carbon storage with high sequestration potential. As patterns of ice loss around Antarctica become more uniform, there is an underlying increase in carbon capture‐to‐storage‐to‐sequestration on the seafloor. The amount of carbon captured per unit area is increasing and the area available to blue carbon is also increasing. Carbon sequestration could further increase under moderate (+1°C) ocean warming, contrary to decreasing global blue carbon stocks elsewhere. For example, in warmer waters, mangroves and seagrasses are in decline and benthic organisms are close to their physiological limits, so a 1°C increase in water temperature could push them above their thermal tolerance (e.g. bleaching of coral reefs). In contrast, on the basis of past change and current research, we expect that Antarctic blue carbon could increase by orders of magnitude. The Antarctic seafloor is biophysically unique and the site of carbon sequestration, the benthos, faces less anthropogenic disturbance than any other ocean continental shelf environment. This isolation imparts both vulnerability to change, and an avenue to conserve one of the world's last biodiversity refuges. In economic terms, the value of Antarctic blue carbon is estimated at between £0.65 and £1.76 billion (~2.27 billion USD) for sequestered carbon in the benthos around the continental shelf. To balance biodiversity protection against society's economic objectives, this paper builds on a proposal incentivising protection by building a 'non‐market framework' via the 2015 Paris Agreement to the United Nations Framework Convention on Climate Change. This could be connected and coordinated through the Antarctic Treaty System to promote and motivate member states to value Antarctic blue carbon and maintain scientific integrity and conservation for the positive societal values ingrained in the Antarctic Treaty System. [ABSTRACT FROM AUTHOR]

As marine-ice around Antarctica retracts, a vast 'blue carbon' sink, in the form of living biomass, is emerging. Properly protected and promoted Antarctic blue carbon will form the world's largest natural negative feedback on climate change. However, fulfilling this promise may be challenging, given the uniqueness of the region and the legal systems that govern it. In this interdisciplinary study, we explain: the global significance of Antarctic blue carbon to international carbon mitigation efforts; the urgent need for international legal protections for areas where it is emerging; and the hurdles that need to be overcome to realize those goals. In order to progress conservation efforts past political blockages we recommend the development of an inter-instrument governance framework that quantifies the sequestration value of Antarctic blue carbon for attribution to states' climate mitigation commitments under the 2015 Paris Agreement. Key policy insights Blue-carbon emergence around Antarctica's coastlines will potentially store up to 160,000,000 tonnes of carbon annually. Blue-carbon will emerge in areas of rich biomass that will make it vulnerable to harvesting and other human activities; it is essential to incentivise conserving, rather than commercial exploitation of newly ice-free areas of the Southern Ocean. Antarctic blue carbon is a practical and prime candidate to build a cooperative, inter-instrument, non-market mitigation around; this should be considered at the 'blue COP' UN Climate change discussions in Spain. Allowing Antarctic fishing states to account for the carbon storage value of blue carbon zones through a non-market approach under the Paris Agreement could provide a vital incentive to their protection under the Antarctic Treaty System. The Scientific Committee on Antarctic Research would be the ideal body to facilitate the necessary connections between the relevant climate and Antarctic governance regimes. [ABSTRACT FROM AUTHOR]