Ocean acidification has emerged over the last two decades as one of the largest threats to marine organisms and ecosystems. However, most research efforts on ocean acidification have so far neglected management and related policy issues to focus instead on understanding its ecological and biogeochemical implications. This shortfall is addressed here with a systematic, international and critical review of management and policy options. In particular, we investigate the assumption that fighting acidification is mainly, but not only, about reducing CO 2 emissions, and explore the leeway that this emerging problem may open in old environmental issues. We review nine types of management responses, initially grouped under four categories: preventing ocean acidification; strengthening ecosystem resilience; adapting human activities; and repairing damages. Connecting and comparing options leads to classifying them, in a qualitative way, according to their potential and feasibility. While reducing CO 2 emissions is confirmed as the key action that must be taken against acidification, some of the other options appear to have the potential to buy time, e.g. by relieving the pressure of other stressors, and help marine life face unavoidable acidification. Although the existing legal basis to take action shows few gaps, policy challenges are significant: tackling them will mean succeeding in various areas of environmental management where we failed to a large extent so far.

Ocean acidification and climate change are linked by their common driver: CO 2 . Climate change is the consequence of a range of GHG emissions, but ocean acidification on a global scale is caused solely by increased concentrations of atmospheric CO 2 . Reducing CO 2 emissions is therefore the most effective way to mitigate ocean acidification. Acting to prevent further ocean acidification by reducing CO 2 emissions will also provide simultaneous benefits by alleviating future climate change. Although it is possible that reducing CO 2 emissions to a level low enough to address ocean acidification will simultaneously address climate change, the reverse is unfortunately not necessarily true. Despite the ocean's integral role in the climate system and the potentially wide-ranging impacts on marine life and humans, the problem of ocean acidification is largely absent from most policy discussions pertaining to CO 2 emissions. The linkages between ocean acidification, climate change and the United Nations Framework Convention on Climate Change (UNFCCC) are identified and possible scenarios for developing common solutions to reduce and adapt to ocean acidification and climate change are offered. Areas where the UNFCCC is currently lacking capacity to effectively tackle rising ocean acidity are also highlighted.L'acidification des océans et le changement climatique sont liés par leur cause commune : le CO 2 . Alors que le changement climatique est la conséquence d'une série d'émissions de gaz à effet de serre, l'acidification des océans à l'échelle planétaire est causée seulement par l'accroissement des concentrations en CO 2 dans l'atmosphère. La manière la plus efficace pour atténuer l'acidification des océans est de réduire les émissions de CO 2 . Agir pour empêcher davantage d'acidification dans les océans en diminuant les émissions de CO 2 entraînera également des avantages simultanés dans l'atténuation de changements climatiques futurs. Alors qu'il est possible de réduire les émissions de CO 2 à un niveau suffisamment bas pour atténuer l'acidification des océans, tout en s'attaquant simultanément au changement climatique, l'inverse n'est malheureusement pas forcement le cas. Malgré le rôle intégral des océans dans le système climatique et les effets potentiels étendus sur la vie marine et les humains, le problème de l'acidification des océans est largement absent de la plupart des discussions politiques liées aux émissions de CO 2 . Les liens entre acidification des océans, le changement climatique et la Convention cadre des Nations Unies sur le changement climatique (CCNUCC) sont identifiés et des scénarios possibles pour développer des solutions communes pour réduire et s'adapter à l'acidification des océans et le changement climatique sont proposés. Les domaines où la CCNUCC manque actuellement de capacités pour lutter effectivement contre l'acidité croissante des océans sont aussi mis en valeur.

Carbon‐dioxide removal (CDR) technologies offer the potential to contribute to the restoration and protection of natural ecosystems, the achievement of development goals and the safeguarding of human wellbeing. However, these technologies can also present risks to biodiversity, particularly those techniques that depend on large‐scale manipulation of ecosystems and earth‐system processes. Debates around the development of these technologies have historically focused on the dichotomy between the need to expand the knowledge base on all options related to emerging technologies, and the concern that research represents a slippery slope to deployment. This paper introduces a new approach to governing CDR research – one based on threat identification. We present a framework for assessing the impacts (positive or negative) on biodiversity and ecosystems from a spectrum of CDR interventions, so as to prioritize research to those CDR options that present minimal threats to biodiversity. Application of the framework indicates that while many CDR interventions present threats to biodiversity, certain options, such as regenerative CDR, may have positive impacts.

The ocean plays a major role in regulating Earth's climate system, and is highly vulnerable to climate change, but continues to receive little attention in the ongoing policymaking designed to mitigate and adapt to global climate change. There are numerous ways to consider the ocean more significantly when developing these policies, several of which offer the co-benefits of biodiversity protection and support of marine-dependent human communities. When developing forward-thinking climate change policy, it is important to understand the ways that the ocean contributes to global climate and to fully inventory the services that the ocean provides to humans. Without more inclusive consideration of the ocean in climate policy, at all levels of governance, policy makers risk weaker than necessary mitigation and adaptation strategies.L'océan joue un rôle majeur dans la régulation du système climatique de la planète, tout en étant aussi très vulnérable au changement climatique, mais cependant continue de ne recevoir que peu d'attention au sein de l'élaboration actuelle des politiques visant à atténuer et à s'adapter au changement climatique. Nombreuses sont les manières de bien prendre en compte les océans dans l'élaboration de ces politiques, certaines d'entre elles offrant des co-bénéfices en matière de protection de la diversité et soutien aux communautés humaines dépendantes des zones marines. Il est important de comprendre, dans l'élaboration de politiques climatiques prévisionnelles, les façons dont les océans contribuent au climat planétaire et de pleinement inventorier les services que l'océan fournit à l'homme. En l'absence d'une prise en compte inclusive des océans dans les politiques climatiques, à tous les niveaux de gouvernance, les décideurs risquent une mise en oeuvre de stratégies de mitigation et d'adaptation plus faibles qu'il ne le faut.

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