Since industrialisation, human activity has contributed to the dramatic increase of carbon dioxide levels in the atmosphere. Most people are aware of the impact that rising levels have on global warming, yet many are less aware about the effect it has on our world’s oceans. Ocean acidification is the ‘other’ CO2 problem and is just as important as rising global temperatures.

Oceans cover over two thirds of the world’s surface and play a critical role in balancing the exchange of gases between the hydrosphere and the atmosphere. They also contribute to the planets biodiversity and livelihood for millions of people across the globe.

Ocean acidification has been gaining more recent attention as scientists learn that excess carbon dioxide from the atmosphere is being absorbed into the ocean’s surface to form carbonic acid (H2CO3). Measured pH levels have already dropped by 0.1 units in the last 200 years, making the world’s ocean 30% more acidic. Trending predictions indicate that a further pH reduction of 0.2-0.3 units is likely to occur by the end of the century unless rising CO2 emissions cease.

Acidification of the world’s oceans have played a major role in three of history’s five major extinctions; the most devastating of which eliminated 90% of marine species at the end of the Permian period 250 million years ago. It is becoming evermore evident that industrialisation is now a major cause of this process through fossil fuel burning, deforestation, land clearing and agriculture.

Enhanced uptake of CO2 reduces the level of carbonate saturation in seawater and impedes carbonate-secreting organisms such as corals to calcify. This poses great threat to highly sensitive marine ecosystems such as coral reefs, which will then require extra energy that is not readily available to sufficiently restore and regrow. If this trend continues, the oceans are set to become 150% more acidic (pH of 7.8) by 2100 than they were pre-industrialisation. When oceans reach this level of predicted acidity, reefs are likely to be less robust and less resistant to climatic change, resulting in a loss of architectural complexity and marine diversity by one third. These predictions are based upon the carbon cycle and the chemical processes of acidification.

Oceans and carbon dioxide

Many scientists term the present period of geological time the ‘Anthropocene’ epoch. Since the beginning of the industrial revolution, humans have pumped 365 billion metric tonnes of carbon dioxide into the atmosphere through fossil fuel burning and an extra 180 billion tonnes through deforestation; this continues to date at an increase of 6% per year. About half of the excess carbon dioxide injected into the atmosphere from fossil fuel burning and land clearing has absorbed into the world’s oceans. Before industrialisation, carbon dioxide levels were at 280 parts per million (ppm) and today they have risen to over 400ppm; higher than any rate seen in the past 800,000 to several millions of years. If trends continue the predicted outcome of 1000ppm could be seen by the end of the century.

A number of studies demonstrate the harmful effects of ocean acidification on marine biodiversity. Research on One Tree Island- the southern most tip of the Great Barrier Reef indicates that coral reefs and other calcareous organisms will be the first major ecosystem to face extinction.

Recent studies have shown that 50% of the Great Barrier Reef has been destroyed over the past three decades. If current emissions continue to follow current trends “all coral reefs will cease to grow and start to dissolve” in the next 50 years.

A report by The Royal Society states that “the only practical way to minimise the risk of large-scale and long-term changes to the oceans, is to reduce carbon emissions” to less than 900 gigatonnes of carbon by 2100. This calls for immediate action and a dramatic decrease in human fossil fuel consumption across the globe.

Without reefs, millions of species may be at risk of facing extinction.

It is unquestionable that humans are contributing to climate change through industrial activities faster than seen in the previous millions of years. An increase in the level of carbon dioxide has caused a disruption in the equilibrium between carbon in the oceans and in the atmosphere.

Although research indicates that ocean acidification has occurred naturally in the past, human activity is accelerating the process far too quickly for marine species to evolve. This will threaten one third of biodiversity in the Earth’s oceans by the end of the 21st century. It is critical for humans to dramatically reduce the release of carbon emissions into the atmosphere in order to prevent such a scenario.

The good news is that is seawater chemistry indicates that calcification will increase if pH levels increase and becomes more alkaline. The bad news is, global carbon emissions do not seem to be decreasing in the atmosphere and we are in fact heading towards threshold levels of 450ppm far too quickly for marine organisms to adapt and evolve. As industry continues to accelerate, carbon emissions will continue to rise, resulting in increased global warming effects and ocean acidification. These factors may lead to the onset of a mass extinction of marine life by one third.

The likelihood of fewer corals reefs in the near future is high. This disturbing prediction means that millions of coral dependant species will be a risk of losing their habitats and food sources, thus contributing to a biodiversity loss of one third in our marine environment.

Other factors including overfishing, terrestrial runoff, coastal deforestation, recreational sports and rising sea temperatures caused by global warming is placing immense stress on marine ecosystems to calcify and repair. All of these factors are a result of human activity. Immediate discussion and effective controls are to be put in place to protect marine life by reducing carbon emissions in the atmosphere.

WRITTEN BY KATHLEEN FUREY
This paper was written after reading “The Sixth Extinction: An Unnatural History” by Elizabeth Kolbert

How can you help?

We have partnered with the Australian Marine Conservation Society (AMCS), dedicated to the protection of Australia’s coastlines. They aim to keep our oceans clean and marine wild-life thriving through scientific research in ways to safeguard the future of our oceans. Their dedication to eliminate climate change, industrial scale fishing and single use plastics have helped build a community and movement to protect endangered species, our coasts and ocean.

Follow their campaigns, sign their call for action petitions to protect our reefs and marine life or make a direct donation by visiting there website marineconservation.org.au.

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