Click image to listen to Michael Krasny’s Forum interview with author Elizabeth Kolbert about her book “Earth’s Sixth Mass Extinction.”
Scientists have figured out that approximately 30% of all of mankind’s excess atmospheric CO2 emissions — more than 1.5 trillion tons of CO2 — has been absorbed by the oceans already. The effect of this carbonization is causing the ocean to become less alkaline, i.e. to have a lowering pH and correspondingly greater acidity. This is causing a fundamental change in the chemistry of the ocean from pole to pole, broadly called “ocean acidification.” Ocean acidification is affecting the entire marine environment, causing increasingly dire impacts on marine life and sea food chains.
Since the industrial revolution, the atmospheric concentration of carbon dioxide has increased from 280 to over 400 parts per million due to the burning of fossil fuels such as coal, gas, and oil, along with land use change. The world’s surface ocean is tightly linked with the atmosphere and absorbs huge amounts of carbon dioxide each year. This exchange, in part, helps to regulate the planet’s atmospheric CO2 concentrations — were it not for ocean uptake of CO2, atmospheric CO2 levels would be increasing at an even greater rate than they are now. But, it comes at a cost for the oceans and ocean life; from the smallest, single-celled algae to the largest whales.
Ocean acidification is causing ecosystems and marine biodiversity to change. Rapidly-shifting ocean chemistry has been widely blamed for observed recent damage to coral reef colonies, which negatively impact the marine food chain and fish reproductive processes for the surrounding areas. These changes have the potential to affect both marine life and food security for the entire planet, as most nations get a substantial portion of human food from the sea. Scientists and policy makers are now concerned that our carbon emissions, which are rapidly changing the oceans’ chemistry, will cause a mass extinction within the oceans as a direct result of what we generally think of as “climate change” but whose impacts are substantially broader and far more devastating than many people widely recognize.
While the CO2 that has already been absorbed has helped to moderate the degree of planetary warming we’ve experienced to date, the ocean’s limited capacity to continue absorbing CO2 from human emissions poses considerable climate “tipping point” risks to humans. Once the ocean capacity to absorb more CO2 diminishes, more of the carbon dioxide we emit will remain in the atmosphere, further aggravating global warming and evincing a rapid acceleration of the rate at which the climate changes. When that happens, few species will be equipped to adapt to such unprecedented rates of climate change.
It is widely believed that the economic impact of continued ocean acidification to be substantial, especially with the risk of collapse of fisheries around the world. Reducing and eventually eliminating our CO2 emissions is the only way to minimize long-term, large-scale risks. Reducing the amount of excess carbon dioxide in the oceans through specific activity to draw down and remove the level of excess carbon, will be the only way to begin to restore full health to the ocean.