The oceans just hit an ominous milestone

You are the product of stability on a planetary scale. About 12,000 years ago, the land held up from a glacial period in the relatively coherent climate that allowed humans to adopt agriculture, literally putting the roots. This stability, however, is now broken, because more than 8 billion people quickly heat the planet, ravage its ecosystems and plus its resources.

In a new report, scientists warn that we have crossed another “planetary border”, a threshold that maintains the systems of the hospital land to life – a kind of global resilience that allows the planet to absorb shocks. This time, it is the relentless acidification of the seas which is crossed in dangerous territory, threatening all kinds of marine people, including organisms at the base of the food canvas. Of the nine total planetary limits, the seventh was violated.

“What this health control shows again and again is that we have an interconnected and interconnected land system,” said Levke Caesar, co-driven by Planetary Boundaries Science Lab of the Potsdam Institute for Climate Impact Research and co-author of the report. “It would actually be deadly if we simply focus on climate change, because, as we see, there are six other limits that have been transgressed. And we also increase the pressure on all these seven limits. ”

Consider a planetary border as a warning panel on a road. At the end of the road is a cliff, representing a tilting point, in which a system of land changes considerably, often irreversibly. Researchers are worried, for example, that parts of the Amazon can approach a transformation of tropical forests into savannas due to climate change and deforestation attacks. If it is the cliff, the concept of a planetary border is a great sign of yellow “cliff”, a warning of scientists that we could approach a catastrophic change.

Or to use another metaphor: a planetary border is your doctor warning you that you have high blood pressure, and the tilting point is the cardiac crisis that has followed. “We set the planetary limits in such a way that as long as we are in the safe operating space, we must prevent the passage of tilting points,” said Caesar.

Before the acidification of the oceans was added to the list this year, the researchers warned that six other borders had already been crossed: the climate changes quickly; Humans use too much fresh water; We lead the species to extinction and transform the biosphere; Forests decrease; The fertilizers pollute water bodies; And “new entities” such as chemicals and plastics are spreading in the environment.

The acidification of oceans is intimately linked to the planetary border of climate change because seawater absorbs carbon dioxide from the atmosphere and has indeed absorbed a quarter of the CO2 emissions of humanity. This helped prevent the planet from warming up even faster, but also creates carbonic acid. Consequently, the report notes that oceanic acidity has increased by 30 to 40% since the generalized burn of fossil fuels began in the industrial era.

It is a new perilous for forms of ocean life. Many organizations, such as corals, molluscs and crustaceans, build shells for protection, but carbonic acid reduces the amount of calcium carbonate available for them. And what they manage to build will be continuously eroded by the increase in the acidity of seawater, which will force them to add new layers to their homes to follow. “Acidification affects many physiologically marine organizations,” said Peter Roopnarine, conservative of geology at California Academy of Sciences, which was not involved in the report. “Whether for a properly functional respiratory system, or to build an external or internal skeleton. It affects all larvae, or the development of these organisms, to adults.”

Acidification and increased water temperatures also cause coral whitening, when organisms are stressed and release the symbiotic algae which provide them with energy. Because scientists have evidence that organizations are already in prejudice, the new report confirms that we have crossed the planetary border for the acidification of the oceans. “There is a real concern that, as our water is used, there will be impacts on fairly important ecosystems on marine calcification species,” said Jennie Rheuban, specialist in Woods Hole Oceanographic Institution, which was not involved in the report.

This acidification could also shake up the very foundations of the oceanic food network. Phytoplankton are tiny photosynthetic organisms that absorb CO2 and expel oxygen, just like plants on earth. Indeed, these plankts engulf half of the kidnapped CO2 in the world by photosynthesis and produce half of the atmospheric oxygen of the earth.

Unfortunately, many species of phytoplankton build shells and may have trouble acing tirelessly. These organizations kidnap carbon charges and serve as a critical food source for small creatures known as Zooplankton, which in turn are consumed by larger animals like fish.

But not all oceans are acidific in the same way. Colder places, such as the Arctic Ocean or in the South which surrounds the Antarctic, more easily acidified than tropical waters. This means that polar regions – which can be distant but host a multitude of species such as whales – could approach a tilting point where organisms are not able to build shells. “The southern ocean is about to give a tip,” said Ken Johnson, a main scientist who studies the region of the Monterey Bay Aquarium Research Institute but was not involved in the report. “Water is changing more quickly. We are ramping to the edge of this tilting point.”

Complete things, planetary borders are often strengthened. In addition to acidification, the lifespan of the ocean faces the violation of the climate border, because the seas absorbed approximately 90% of the excess heat that humans added to the atmosphere. This has regularly increased the average ocean temperature, but also causes extreme marine heat waves, further stressing organisms there. (Oxygen concentrations also drop as temperatures increase, aggravating their pain.) They are also dealing with the border “Introduction of new entities”, because chemicals and plastic pollution hurt and kill ocean species.

These overlapping crises make it not only more difficult for organizations to survive, but can also make it more difficult for the ocean to continue to sequence the carbon. This is what Caesar and his colleagues will then explore. “What’s going on under these different stressors?” Caesar said. “Because it is not only the acidification of the ocean. The ocean also loses oxygen. It warms up. How does this have an impact on this buffer of the ocean?”

The good news is that by quickly reducing greenhouse gas emissions, we can withdraw from the cliff for the acidification of the ocean. In fact, human intervention is the reason why 2 of the 9 planetary borders have not been crossed. Ozone levels in the stratosphere are now at safe levels, notes the report, thanks to international agreements prohibiting substances from ozone. And atmospheric aerosols are also in the safe operating space, thanks to the countries to better regulate the burn of dirty fuel such as coal and the transition to renewable energy such as solar energy and wind.

The number of overlapping and strengthening problems makes the ocean a particular challenge. But by doing things like restoring coastal ecosystems and reducing plastic pollution, humans can reduce the pressures we put on them. “It can be very difficult to solve, solve these problems when there is no miracle solution where you change one thing and you solve all the problems,” said Rheuban. “There are a number of different problems that must be resolved.”