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The final warning from the Earth

Green Country Vol. 117 (Dec 2015)

The United Nations Climate Change Conference was recently held in Paris. World leaders and climatologists finally reached an agreement. Whether or not the agreement will be truly effective at reducing global carbon emissions remains to be seen. Meanwhile, the Earth is issuing the last warning to us - ocean acidification. The causes of ocean acidification and global warming are similar, mostly arising from the enormous amount of carbon dioxide produced by human activities. Water bodies absorb carbon dioxide (CO2) which dissolves and undergoes a chemical reaction with the water (H2O) to become carbonic acid (H2CO3). Carbonic acid can release hydrogen ions (H+) in water. As the concentration of hydrogen ions rises, so too does the water's acidity.

Oceans comprise the major storage bank of carbon dioxide across the globe. They hold over 50 times more carbon dioxide than the atmosphere. Since the beginning of the Industrial Revolution, however, with large scale burning of fossil fuels that discharges carbon dioxide, the oceans have absorbed over 50 billion tonnes of carbon dioxide in the past 250 years, increasing acidity by 30%. If ocean acidity continues to rise at the current rate, marine biosphere will be seriously affected, including erosion of coral reefs, and inhibited growth of algae as well as shellfish exoskeletons. As creatures at the bottom of the food web are harmed and reduced in numbers, the overall ocean food web will be profoundly affected.

Earlier this year, a report on the largest scale species extinction in the geological history of Earth was published in the journal Science. It pointed out that the eruptions of volcanoes in the Siberian Trap 252 million years ago had released large amounts of carbon dioxide, which acidified the oceans and led to the extinction of over 90% of ocean creatures and two-thirds of terrestrial species. Today, the release of carbon dioxide is on par with the Siberian Trap volcano eruptions. If we do not achieve large scale carbon reductions across the world, another mass extinction looms.

Text | Hayward Ng