Ocean acidification - Facts and figures

Ocean acidification – a direct consequence of increased human-induced carbon dioxide concentrations (CO2) in the atmosphere – is a threat to the integrity and diversity of the ocean and the many services and benefits it provides to society. Ocean acidification occurs when CO2 reacts with sea water to produce an acid. The faster the increase of CO2 in the atmosphere, the faster the acidification of the ocean.

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Key facts about ocean acidification

  • Currently, each year the ocean absorbs approximately 25% of all the CO2 emitted by human activities.
  • Ocean acidity has increased by about 30% since the beginning of the Industrial Revolution and if CO2 emissions continue to grow, the rate of acidification will accelerate in the coming decades. This rate of change, to the best of our knowledge, is many times faster than anything experienced in the last 250 million years.
  • This hidden ocean ‘service’ has been estimated to represent an annual subsidy to the global economy of US$86 billion per year, though there is considerable uncertainty around this figure.
  • Numerous animals and plants in the sea have calcium carbonate skeletons or shells. Many are sensitive to small changes in acidity, particularly at young life stages and there is evidence that some of these calcifying species may already be affected. Physiological processes and behaviour also show sensitivity to ocean acidification in other species.
  • Some marine organisms may benefit from ocean acidification (e.g. some non-calcifying photosynthetic algae as well as other marine plants like seagrasses). However, it is important to bear in mind that even positive effects on one species can have a disruptive impact on food chains, community dynamics, biodiversity and ecosystem structure and function.
  • Many of the most sensitive species are directly or indirectly of great cultural, economic or ecological importance; for example, warm-water corals that reduce coastal erosion and provide habitat for many other species.

What needs to be done?

  • Significantly reduce global CO2 emissions.
  • Reinvigorate action to reduce, or - where possible - prevent or eliminate, at a regional or local level, other environmental pressures, such as overfishing, pollution, nutrient loadings and eutrophication which are considered to magnify the impacts of acidification.
  • Strengthen ocean resilience by allowing the ocean space and time for recovery from human impacts, through designating and ensuring protection of an effective network of marine protected areas and by implementing effective marine planning.
  • Support the international coordination of integrated ocean acidification research.

What is IUCN doing?

International policy
IUCN recognizes the benefits of addressing ocean acidification and climate change in a synergistic manner and therefore commits to exploring ways to address the concerns related to ocean acidification in its policy and outreach engagement within international policy fora such as the United Nations Framework Convention on Climate Change (UNFCCC).

IUCN advocates for policy coordination and coherence in addressing ocean acidification by supporting dialogue and development of necessary linkages between relevant conventions, policy processes and institutions, including the UNFCCC, the Convention on Biological Diversity (CBD), the London Dumping Convention and the United Nations General Assembly (UNGA).

IUCN also runs one of the major global mechanisms to enable the effective science policy exchanges required to underpin international, regional and national actions. This is through the Chairmanship from Dan Laffoley, IUCN 's Principal Advisor on Marine Science and Conservation, of the International Reference User Group on Ocean Acidification (iOA-RUG). This body brings together science and policy leaders in an effective way and has already supported programmes such as EPOCA, UKOA, MedSEA and Bioacid, as well as delivering major global outreach activities through the likes of Google and supporting new partnerships, for example with the X PRIZE.

National activities
IUCN is exploring ways to work with countries to design appropriate climate change mitigation and adaptation strategies and natural resource management policies and practices, consistent with implementing the provisions of UNFCCC and other international commitments, which take full account of the threat posed by ocean acidification to biodiversity and coastal livelihoods.

IUCN will support the development and implementation of effective strategies for ocean, coastal and fisheries management, to reduce environmental impacts of acidification, thereby also improving the resilience of marine ecosystems and dependent livelihoods, giving them a better chance to respond and to adapt to the impacts of climate change.

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