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Our dependence on fossil fuels is not only disrupting the global climate, it is also causing the rapid acidification of the world’s oceans. A situation that currently appears irreversible and whose consequences for marine life are still unknown.
To illustrate this phenomenon, two scientists decided to transpose the data on the reduction in pH into bands of different colors that can demonstrate how much ocean acidification has worsened between 1982 and 2024, a period during which the rate of acidification has accelerated compared to previous decades.
“We wanted to create these strips to use as a tool to raise public awareness of what we are seeing, which is the rapid progression of ocean acidification,” summarizes the Duty one of the ideators, Nicolas Gruber, a specialist in environmental systems and professor at the Zurich Polytechnic in Switzerland.
It should be noted that this phenomenon is mainly explained by the fact that the oceans absorb around 30% of CO emissions.2 attributable to human activity, mainly the massive use of fossil fuels since the beginning of the industrial era. This situation has the effect of reducing the pH of the water, and therefore gradually acidifying it.
Precariousness
The project by Nicolas Gruber and his colleague Luke Gregor, called Ocean Acidification Stripes, is inspired by the Warming Stripes, which in just a few years have become the symbol of the scale and speed of global warming.
As with rising temperatures, the illustration of the situation in the different ocean basins of the planet aims to demonstrate that the phenomenon “is not abstract,” summarizes Mr. Gruber. “The bands illustrate the precariousness of the ocean waters and the speed of changes since the beginning of the 1980s.”
Martine Lizotte, a research scientist in ocean biogeochemistry at Fisheries and Oceans Canada (DFO), agrees. “These figures provide fairly convincing evidence of ocean acidification,” she points out.
“We see in the graphs that the decrease is constant, which shows a long-term trend in ocean acidification. The rate is not linear, which indicates in particular that it could accelerate over time,” adds Mr.me Lizotte.
The pH of the oceans has remained “relatively stable” for 50 million years, at about 8.25, explains the DFO researcher. “It’s only since the Industrial Revolution that we’ve seen a reduction in pH. Between 1750 and 1985, we went to 8.14. That average reduction represents a 30% increase in acidity. And now we see that the rate of pH reduction has increased. From 1750 to 1985, we were losing 0.005 pH units per decade. But between 1985 and today, the average is 0.07 per decade. So that’s three times faster over the last 40 years.”
The average pH of the oceans, which is calculated on a logarithmic scale, is now between 8.05 and 8.06, while acidity has increased by 18% since the early 1980s.
And there is no indication that this downward trend can be reversed at the moment, adds Mr.me Lizotte. “As CO levels continue to rise2 “Atmospheric acidification caused by human activity is the main driver of acidification, reversing the trend would require significant reductions in greenhouse gas emissions.”
But even assuming a rapid transition away from fossil fuels, so as to radically reduce our CO emissions2the researcher warns that “complete reversal of ocean acidification could take hundreds or even thousands of centuries. In that case, the potential extent of the damage, which is not yet known, could be irreversible. But we don’t know that.”
Concerns
One thing is certain: this reduction in the pH of marine environments raises several questions, but also very real concerns, among scientists. According to Professor Emeritus Alfonso Mucci, from the Department of Earth and Planetary Sciences at McGill University, this acidification risks disrupting ecosystems and threatening part of the biodiversity of the oceans.
For example, organisms that need to form a shell as they grow may no longer be able to do so. This is particularly the case for some crustaceans. Fish and zooplankton species that are essential because of their role at the base of the food chain may also suffer or even die. “This could change the marine food chain and affect other organisms that feed on these organisms,” says Mucci.
As with the climate crisis, the worst is likely to come, he warns. “There are places in the world that are no longer suitable for these organisms, and even the reefs are dissolving in these environments. If this trend continues, by the end of the century, coral reefs will no longer be able to calcify, and therefore grow. All of these ecosystems will then dissolve in the following decades.” Yet the world’s coral reefs alone are home to 30% of known marine species.
How can we hope to tackle this growing problem, which also directly affects Canadian waters, particularly those of the St. Lawrence Estuary and Gulf? “We should stop emitting CO2 in the atmosphere, period,” says Alfonso Mucci.
The latter and Mme Lizotte also warns against projects that raise the idea, for example, of dumping substances into the oceans that would neutralize the effects of CO2or to stimulate the growth of phytoplankton, which absorbs this greenhouse gas. At present, the cost and possible feasibility of such operations are unknown.