Ocean acidification is global warming’s forgotten crisis
Most of us are familiar with the climate change impacts we see and feel in our communities: heatwaves, storms, droughts, floods, and so on.
But a UN meeting this week about climate change and oceans reminds us a related crisis is unfolding largely away public attention: the one-two punch of ocean warming and acidification.
With record temperatures sweeping over continents year after year, it is easy to overlook that the ocean has absorbed some 90% of the heat trapped by the carbon dioxide dumped into the atmosphere since the industrial revolution; and how much of that CO2 has dissolved into seawater as carbonic acid, altering its basic chemistry.
The UN meeting follows on the heels of a new secretary general report that investigates the impacts of these changes and the findings are concerning, to say the least.
The report describes record ocean temperatures pushing fish species toward cooler latitudes and out of reach of artisanal fishers; it documents widespread coral bleaching across the tropical belt and how most reefs could enter a state of permanent decline by 2040; it shows how ocean acidification has damaged a range of calcifying marine life, such as corals and shellfish; and it raises fears that the cumulative effects of the impacts are degrading phytoplankton, zooplankton, and krill, the foundation of the ocean’s food chain.
A sea snail shell is dissolved over the course of 45 days in seawater adjusted to an ocean chemistry projected for the year 2100.
Ocean acidification can now be seen from space, highlighting an ongoing danger of climate change and revealing the regions most at risk.
Seawater absorbs about a quarter of the carbon dioxide, a greenhouse gas, that humans release into the atmosphere each year, mostly from the burning of fossil fuels, according to the National Oceanic and Atmospheric Administration (NOAA). This process has slowed the warming of the globe, as all of that carbon is locked up in the ocean’s “carbon sink” rather than floating freely in the atmosphere. But when seawater takes up carbon dioxide, it becomes more acidic. According to NOAA, the surface pH of the ocean has become 30 percent more acidic since the end of the Industrial Revolution.
A map created from the results of satellite gathered information shows the variation apparent across the globe. The redder the colour, the more alkaline, or basic — the opposite of acidic — the region is. The more basic the seawater, the more room it has to absorb carbon dioxide without becoming overly acidic. Open regions of the ocean show this resilience, while many coastal regions appear less alkaline. The northeastern United States looks particularly vulnerable — a finding that echoes 2013 research using on-the-ground measurements.
Ocean acidification eats away at the shells of mussels, oysters and crabs, and baby oysters are already dying in some regions from it. These detrimental effects can carry up the food chain. Meanwhile, researchers worry about direct impacts on non-shelled ocean life as well. A 2013 study published in the journal Proceedings of the Royal Society B found that fish kept in acidic water acted more skittish than fish in normal seawater, which could affect their survival in the wild.
Acid Oceans From Greenhouse Gases Threaten Extinctions
The world’s oceans are now more acidic than they have been for at least 300 million years, which scientists who made the discovery warn poses a threat of mass extinction of marine species worldwide.
The change in the ocean’s chemistry is said to be due to carbon dioxide emissions from the burning of fossil fuels.
This, combined with overfishing and pollution, imperils marine life on which billions of people depend for food and jobs.
That warning by the International Program on the State of the Ocean came after an international audit of the health of the oceans revealed the magnitude of the man-made threats.
Program officials caution that Earth’s next mass extinction may have already begun in the oceans.
They warn that coral is especially sensitive to changes in pH levels in the water, and it provides the habitat countless fish and other species depend upon to survive.
Findings published in the program’s State of the Oceans report say that there is a lag of several decades between CO2 being created by human activities and the resulting ocean acidification.
This means that even if world leaders drastically reduced emissions now, further acidification and warming of the oceans are inevitable.
Acidic Arctic Threatening Marine Life
Global greenhouse gas emissions have caused the level of acidity in the Arctic Ocean to rise 30 percent since the dawn of the Industrial Age, threatening to bring dire consequences to the region’s fragile ecosystem.
Delegates to the Arctic Monitoring and Assessment Program conference in Bergen, Norway, were told that the pollution has caused pH levels to reach their lowest levels in the Arctic for at least the last 55 million years.
The Arctic is most vulnerable to acidification because its cold waters can absorb more carbon dioxide.
Its extensive freshwater inflow also makes it less able to chemically neutralize the acidification effects of the greenhouse gas.
It would take tens of thousands of years for the Arctic Ocean to return to the acidity levels that prevailed before the mid-1800s even if all CO2 emissions were halted today, scientists say.
The current acid levels threaten some species with a direct risk of extinction, and fish stocks may also be affected.
Coral reefs around the world are under severe threat.
Caribbean corals are under immediate threat and urgent action was needed to limit pollution and aggressive fishing practices. Average live coral cover on Caribbean reefs has declined to just 8 percent today compared to more than 50 percent in the 1970s.
As more and more carbon dioxide is absorbed from the atmosphere, sea water turns more acidic which can hinder calcification which is crucial for corals’ growth.
Warmer sea surface temperatures are likely to trigger more frequent and more intense mass coral bleaching, which is when reefs turn pale. Although corals can survive bleaching, if the heat persists they can die. This happened in 1998 when 16 percent of corals were lost in a single, prolonged period of warmth worldwide.
Warmer ocean temperatures and acidification are also placing the Great Barrier Reef off Australia under stress.
Coral reefs are home to almost a quarter of the world’s ocean species, they provide coastal protection and can support tourism and fishing industries for millions of people worldwide.