Carbon dioxide (CO2) is a valuable component in our atmosphere as plants utilize it for photosynthesis. Historically, the consumption and production of CO2 was always in balance. However, nowadays due to accelerated burning of fossil fuels and increased deforestation, CO2 is being produced at a rate much higher than the capacity of plants to naturally absorb it. Carbon pollution in the environment not only affects the global climate and leads to the greenhouse effect, it is also contributing to oceans becoming acidic all over the world. Since the Industrial Revolution, CO2 emissions has increased to an extent where a third are being absorbed by oceans, which has consequently reduced the pH balance of ocean waters by about 0.1 units. Although this eliminates the risk of carbon accumulating in the atmosphere, it causes major changes in the chemistry of the oceans.
Ocean acidification is described as the decrease in the pH level of the oceans, which is caused by uptake of CO2 from the atmosphere. When CO2 is absorbed into water at a higher rate, it reacts with water molecules to form carbonic acid. The compound then degrades into a single hydrogen ion (H+) and a bicarbonate ion (HCO-). The presence of these hydrogen ions leads to a decrease in pH or the acidification of the ocean. Initially, scientists all over the world did not worry about ocean acidification because of the assumption that rivers carry sufficient dissolved chemicals from rocks to the ocean, hence ensuring the stability of the ocean’s pH level. However, excess CO2 in oceans is affecting the natural buffering from rivers and as a result the pH level of surface waters is lowered. Ocean acidification has a higher tendency to adversely impact marine life, as they cannot adapt to a drastically changing pH level, which affects their biochemical functioning. Furthermore, this process reduces carbonate ions, which makes it difficult for species like oysters, mussels, corals and other shelled organisms to form shells and skeletons. The existing shells of such species also lose density. In the case of coral reefs, the weakened shells due to lower pH may make reefs more sensitive and susceptible to storm damage and slow rate of recovery.
Ocean acidification affects humans as well. Altering ecosystems can have grave consequences on humans in the form of loss of employment and livelihood, revenue declines and other indirect economic costs. Firstly, ocean acidification can cause risks to food security because people all over the world consume molluscs and oysters, and ocean acidification leads to a loss of both these species. Secondly, ocean acidification effects are a menace because generally, coral reefs play their part in protecting shorelines from destructive storms and cyclones and are valued at US$9 billion per year. If we ensure protection of coral reefs, we can ensure our own prevention from loss of life, property damage and erosion. Furthermore, the tourism industry could be highly affected. For example, the Great Barrier Reef Marine Park attracts a lot of tourists annually and helps to contribute US$ 5.4 billion to the Australian economy.
Lastly, ocean acidification can be alarming if oceans keep absorbing CO2 from the atmosphere until the capacity for absorption ends and we are left with extremely acidic oceans, which do not play an effective role in keeping climate change balanced.
The projected expectation is that in the future, acidification of oceans will not be uniform all over the world. It is predicted that upwelling regions and seas in polar regions will acidify faster than temperate or tropical regions. A lot of surface waters will continue to corrode with each decade and the pH level will differ from ecosystem to ecosystem. In some areas of the Arctic, water is already extremely acidic, due to which corrosive events have taken place. The acidity of seawater could potentially increase by 0.4 units.
Ocean acidification takes place on a very broad scale and would require comprehensive measures for mitigation, which require more time and effort. As ecosystems are strongly connected together, policymakers should come up with a strategic and inclusive approach to tackle acidification. Reduction of greenhouse gases is indeed the most viable solution to ocean acidification, but undertaking some decisions and actions could help prepare for the negative effects of ocean acidification. Policymakers and relevant organizations can help enable marine ecosystems to cope with environmental changes and prevent local stressors causing negative effects. Some mitigation measures could involve working on enhancing water quality such as proper quality assurance of runoffs and pollutants from fertilizers, which often contribute to acidification. Furthermore, technology should be upgraded, for example, new forecasting systems should be introduced that cause seawater at the bottom of the sea to be brought up to the ocean surface in order for avoid shellfish mortality. More attention should be paid to managing habitats sustainably, such as proper application of marine spatial planning, decreasing sediment load and enhancing the protection of coasts from more damage. Conservation biologists should also be involved at the national level to ensure protection of species, which are vulnerable and sensitive to the prolonged effects of ocean acidification.
Zoha Gardezi has a degree in Environmental Sciences and is a development practitioner.