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Ocean Acidification: Climate Change’s Evil Twin

20 July 2018

GEP Student Blog

We are all aware of climate change, but we need to talk more about ocean change, and the effects of acidificationPeter Thomspon, UN Ambassador for the Oceans[1].

What is ocean acidification?

Ocean Acidification is a relatively new issue on the environmental agenda and it requires urgent attention and action from the international community. Our oceans act as biological pumps by absorbing carbon dioxide (CO2) from the atmosphere.

Figure 1. Ocean Acidification Graph
Credit: NOAA PMEL Carbon Program

Since the beginning of the industrial revolution, 250 years ago, carbon emissions have increased significantly (fig. 1). Oceans have been absorbing up to 30% of these emissions leading to accelerating ocean acidification (fig. 2).

In scientific terms, when COmolecules dissolve in water, there is a release of hydrogen ions and a destruction of carbonate ions. This has two effects : First, hydrogen ions lower the pH value of oceans which increases their acidity (see figure 1); Second, marine organisms (corals, shellfish, etc.) have less carbonate ions available to develop their shells and limestone skeletons. The combination of these two chemical disturbances is known as ocean acidification or OA.

Figure 2. The pH scale
Credit: Kemi Portalen

The average pH of oceans has dropped from 8.2 to 8.1 since the industrial revolution, which may not seem a lot, but corresponds to an increase in acidity of about 26% [2]. While ocean acidification is driven by the same fossil fuel emissions as climate change, it requires specific attention.

How does OA perturb marine life?

Above a certain level of acidity, sea water can become corrosive to limestone, which is an essential component of corals and shellfish (mussels, oysters, etc). In addition, a reduction of carbonate ions means there are less resources available for corals and shellfish to develop and rebuild their structures. 

The survival of corals is especially important, as they provide habitat and food for 25% of all marine life on the planet, including the fish we eat. While the greatest damage is likely to occur in the next few decades, the effects have already been observed on some species (see fig. 3). OA will lead to increased biodiversity loss, which will have adverse effects on us [2]. To learn more about the incredible ecosystem put at risk by ocean acidification, you can watch the BBC documentary series on marine life, Blue Planet II [3].     

Figure 3. Coral Reef before and after ocean acidification, Puerto Rico.
Credit: Ryan Moyer

How does this affect us?

A reduction in coral can have serious impacts on the livelihood and protection of coastal populations. Indeed, coral reefs protect coastal cities and communities from ocean waves, and this puts small-island states particularly at risk [4]. The ocean is also a source of protein, which 3 billion people depend upon. OA will impact the growth and availability of fish and shellfish. This will make the effects of OA visible on our plates, with impacts on global food security. As for the economy, OA will adversely affect the fishing industry, which currently represents $3 trillion per year or about 5 per cent of global GDP, employing 200 million people worldwide [5].

What is being done about OA?

The Scientific response

A large part of the action taken to date has revolved around scientific research to better understand the problem. A scholar in International Relations, Peter Haas, has assessed the role that an epistemic community can have in generating a shared understanding of environmental issues. His research suggests that communities of like-minded scientists frame issues for political action and provide solutions to tackle them [6]. In the case of OA, the first global acknowledgment of OA was in 2004 during the first “Ocean in a High CO2 World” meeting. Since then, research on OA has intensified, and there have been three follow up meetings. Policy makers have joined the table, and following each meeting a “Summary for Policymakers” has identified the key findings [7]. This research is being encouraged by some governments, for example, Germany launched an 8 year research programme, “BIOACID” (Biological Impacts of Ocean Acidification), in 2009 [8]. This confirms the strong link between science and politics highlighted by Haas: the scientific community has brought the OA issue into the spotlight for political action. The question is, are the scientific findings leading to concrete action?

Political Action

The Ocean Conference 2017
Credit: United Nations       

OA has only recently been acknowledged as a serious issue by the international community. In June 2017, the United Nations’ Committee on Ocean Action held a conference entitled “Our Ocean, Our Future: Call for Action”. The final conference report identified 70 initiatives committed to fighting OA, which are identified on the UN website [9].

Concern over OA was also voiced at the UN Climate Change Conference in Bonn in November 2017, by the presiding government, Fiji. As an island state, Fiji is particularly vulnerable to OA, which increases its moral authority and legitimacy to urge action on the issue.

How can we take action on OA?

As fossil fuel consumption is the source of OA, reducing our carbon emissions is the main path to action. This means that greening our energy consumption should not only be directed at tackling climate change, but also ocean change. OA is not yet a central issue of public debate, but we could help here by spreading the word around us. We can also engage with organizations, such as GreenPeace or WWF, to petition against big polluters. Finally, as citizens, we can use our vote to elect candidates and parties who are attentive to environmental issues. As individuals, we might not always feel influential enough to make a significant difference, but we can elect a person who has the will and authority to speak up on the OA issue.


[1] Fiona Harvey. 2017. Ocean acidification is deadly threat to marine life, finds eight-year study. The Guardian. 23 Oct 2017. Available at: [Accessed 17/03/2018]

[2] Euzen, A., Gaill, F., Lacroix, D. and Cury, P. 2017. The Ocean Revealed. Paris: CNRS Editions. Available at: [Accessed 17/03/2018]

[3] Blue Planet II. 2017. BBC. Available at:

[4] UNFCCC. 2017. Climate Action Is Needed to Protect World’s Oceans: First UN Ocean Conference in New York 6 June 2017. Available at: [Accessed 17/03/2018]

[5] United Nations. [No date] Goal 14: Conserve and sustainably use the oceans, seas and marine resources. Available at: [Accessed 17/03/2018]

[6] Haas, P. M. 1990. Obtaining International Environmental-Protection through Epistemic Consensus. Millennium: Journal of International Studies 19:347-63

[7] Third Symposium on the Ocean in a High-CO2 World. 2013. Ocean Acidification: Summary for Policymakers. Available at: [Accessed 17/03/2018]

[8] Federal Ministry of Education and Research. 2016. Ocean Acidification The Other Carbon Dioxide Problem. Available at: [Accessed 17/03/2018]

[9] United Nations. [No date] Communities of Ocean Action: Implementation of Sustainable Development Goal 14. Available at: [Accessed 17/03/2018]