The growing acidity of the world’s oceans could cost the global economy $1 trillion by 2100 if humans don’t stop putting so much carbon dioxide into the atmosphere, according to an extensive report compiled by 30 experts worldwide and released Wednesday by the U.N. Convention on Biological Diversity.
Oceans have absorbed so much carbon dioxide emitted from power plants, deforestation, manufacturing, and driving, that their acid levels have increased by a staggering 26 percent over the last 200 years, the report said. The disruption of the ocean’s natural pH levels are directly impacting the health of marine life and ecosystems and scientists emphasize that if these trends continue unchecked, it could be both horribly detrimental for the world economy and largely irreversible for thousands of years.
“The oceans are facing major threats due to rising levels of carbon dioxide in the atmosphere,” said Braulio Terreira de Souza Dias, the Convention’s executive director, in a statement accompanying the report. “In addition to driving global climate change, increasing concentrations of carbon dioxide affect ocean chemistry, impacting marine ecosystems and compromises the health of the oceans and their ability to provide important services to the global community.”
Wednesday’s report is intended to be the most up-to-date compilation of what we currently know about ocean acidification — one of the biggest and least talked about effects of global warming — and what we know so far about its effects. It draws on hundreds of peer-reviewed papers published in the last few years to provide a comprehensive guide. Here are some of its most important takeaways.
More than a quarter of all CO2 emitted is absorbed by the ocean
Not all greenhouse gas emissions from power plants and other sources end up in the atmosphere. According to the report, more than 25 percent of all carbon emissions are absorbed into the ocean. When the carbon enters the ocean, it dissolves, forming carbonic acid. The carbonic acid then dissociates, and forms bicarbonate ions and hydrogen ions. As the hydrogen ions increase, so does the ocean’s acidity.
The acidity that results does not mean that the ocean is actually acid, or falling below a pH level of 7.0. The term “acidification” refers only to the process of the oceans becoming less alkaline than they were previously. It is possible, however, that oceans could eventually fall into the acid category if emissions keep rising over the next 100 years.
An acidic ocean hurts marine life, and therefore hurts the economy
Increased ocean acidity impacts the ocean in a number of ways. Directly, it can make it harder for coral and some plankton to produce their skeletons and shells, and increase the risk of those shells dissolving. Acidification can also change the behavior of marine fish and some invertebrates, making them more susceptible to predators. The U.N. study cited reef fish larvae as an example, observing that fish exposed to elevated CO2 lost their abilities to distinguish between different habitat types, to distinguish between kin and non-kin, and to smell predators. Fish, the report said, become “no longer able to learn.”
In all, acidification harms ocean ecosystems, which is bad for humans because ocean ecosystems “help create human well-being and economic wealth,” the report says. Specifically, ocean ecosystems support a number of industries: commercial fishing, shellfishing, tourism, leisure and recreation. Reduced coral health can impact their natural defense of erosion, making it more costly to maintain coastlines.
The U.N. report admits that more research needs to be done on the extent of harm that will be done to these industries because of acidification, and the uncertainty makes it difficult to estimate the economic impacts. At least one study, though, determined that the global economy would lose up to $1 trillion in services like coastline maintenance by 2011, just because of impacts on coral reefs. Those estimated losses don’t include effects on tourism or other industries.
The economic impacts of ocean acidification are already being felt
The U.N. report cited “strong evidence” that acidification is already negatively impacting shellfisheries off the northwest coast of the U.S., partially because the pH of the water there is already so low. Oyster hatcheries in Oregon and Washington, the report said, have been suffering high death rates in larvae — up to 80 percent — since 2006. The pH of the hatchery’s water are “major factors” affecting that death rate, the study said.
The problem at one point threatened the viability of that industry, which the report says has a total economic value of about $280 million every year.
Fortunately, those businesses have been able to recover their operations for now. “The oyster hatcheries have now adapted their working practices so that they avoid using very low pH seawater, either by re-circulating their seawater or treating their water during upwelling events,” the report said. “With these new practices, the north-west coast oyster hatcheries are producing near to full capacity again.”
If we don’t stop acidification soon, fixing it could take thousands of years
One of the most jarring aspects of the U.N. report is its observations of historical evidence to see how long it would take to restore oceans to normal after an acidification period. The Paleocene-Eocene Thermal Maximum (PETM), or about 56 million years ago, likely had carbon content closest to the content we have today, the report said.
It’s not a perfect analogy, the report says, as the carbon that was concentrated in the ocean 56 million years ago was naturally accumulated over thousands of years, not man-made over tens or hundreds of years like today. Back then, an estimated 2000–3000 petagrams of carbon was released into earth’s atmosphere over 10,000 years. Now, the IPCC predicts the world will release 5000 petagrams of carbon into the atmosphere over the next 500 years if we follow a “business as usual” scenario.
The geological record shows that it took approximately 100,000 years for the oceans to return to the pH level we now consider to be “normal” after the PETM. That leads scientists to believe that, absent some sort of remedy, it could take a similar amount of time for our ocean to return back to normal as well.
“We can see that ocean acidification is not a short-lived problem,” the report reads, “and [it] could take many thousands of years to return to pre-industrial levels even if carbon emissions are curbed.”