The oceans in danger
Debris on a beach in the Cocos Islands.
© University of Tasmania / AFP / Silke Struckenbrock
Text by: Nenad Tomic
7 mins
The oceans represent 70% of the surface of our planet.
At the origin of life and its preservation, the oceans play an essential role in regulating the climate and represent an essential resource in the food chain.
Moreover, coastal territories are home to more than half of the world's population.
All of humanity depends on the marine environment as it is increasingly vulnerable to climate change, threatened by pollution, acidification or even rising water levels: all factors that jeopardize the fragile balance ecosystems.
The One Ocean Summit in February 2022 is an opportunity to discuss the future and actions to preserve this natural environment.
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A primary factor in planetary balance
In the context of global warming where the quantities of carbon dioxide (CO2) are pointed out, it is worth remembering that around 25% of CO2 gas is absorbed by the oceans.
So many less quantities in the atmosphere which is warming up exponentially.
In addition, the ocean plays a decisive role in the climate on a global scale.
Thanks to its continuous exchanges with the atmosphere, the marine environment absorbs most of the heat (about 90%), so much so that it is possible to measure the extent of global warming by observing the quantities of energy stored in the ocean.
This interaction between the atmosphere and the ocean is also essential in the formation of the different types of climates that reign over the globe.
However, this very fragile balance is now compromised, causing unusually intense and violent climatic phenomena.
The ocean is also very often nicknamed "the cradle of humanity" because of the first appearances of life forms.
It is above all the main food resource for species living in the marine environment, but also for humans.
More than 55% of the population lives near water (oceans and seas) and depends directly on it.
Greenhouse gases and ocean acidification
For several decades, researchers have been looking into the problem of the concentration of greenhouse gases and in particular the increase in carbon dioxide: this phenomenon causes ocean acidification on a global scale.
The observation by researchers from the University of Edinburgh in Scotland is appalling: for 50 years, the pH (the indicator of the acidity of liquids) has dropped by 1°.
The consequences could be disastrous in the long run.
Indeed, a small increase in acidity due to too much absorption of carbon dioxide by water, contributes to the dissolution of calcite and all forms of calcium carbonate which make up half of all living species. in the oceans.
The first to be affected are plankton and coral reefs.
Gold,
these species are at the base of the marine food chain that simply supports life.
Without these marine organisms, all other living beings would be deprived of food (fish, whales, birds, etc.).
Without plankton, the oceans lose their ability to absorb large quantities of CO2 from the atmosphere, making it unbreathable for other living organisms.
At the same time, coral reefs are bearing the brunt of the phenomenon of acidification.
For thirty years, scientists have noted the 50% reduction in coral cover in the world.
The effect is most noticeable around Australia and in many atolls in the Pacific Ocean.
Their role is nevertheless essential in the protection of small tropical islands against their marine submersion.
According to Gilles Bœuf, President of the National Museum of Natural History and holder of the Chair of Sustainable Development, in the case of an average increase in ocean temperature of only 1.5°C, humanity risks losing another 70% remaining corals.
A dive instructor from the Ocean Freedom dives on the Great Barrier Reef in Australia, September 22, 2014. © AFP / William West
The rise in water level
The melting of glaciers in Antarctica and Greenland is the direct consequence of global warming.
The acceleration of this phenomenon has been notable over the past thirty years.
Recent satellite images from NASA and the European Space Agency (ESA) show that the retreat of these two glaciers is now six times faster than in 1990. While these two regions lost around 80 billion tons of ice per year in the 1990s, this figure has multiplied over the past decade: 475 billion tonnes of ice disappear each year in Greenland and Antarctica alone.
According to the latest report from the Intergovernmental Panel on Climate Change (IPCC), this accelerated melting risks raising the level of the oceans by 71 centimeters by 2100,
what was previously imagined as the worst-case scenario.
As a result, more than 400 million people would be exposed to devastating, if not permanent, coastal flooding by the end of the century.
© FMM Graphic Studio
The IPCC also warns of an increase in average atmospheric temperature of 3°C which can cause sea levels to rise by more than one meter.
In addition, the melting of the ice on the poles leads to a gigantic influx of fresh water into the oceans, which directly threatens the circulation of currents.
Thus, in the North Atlantic, scientists have already observed the slowing down of the famous Gulf Stream.
Any notable modification of this current could considerably modify the climate in Europe, but also on the American continent.
Pollution, the other enemy of the ocean
Plastic, chemical or oil pollution puts a strain on marine ecosystems.
According to several studies, every year, 8 million tons of plastic waste ends up in the seas and oceans.
Thus, a few years ago, we witnessed the discovery of the “7th continent” in plastic.
Located in the North Pacific, between Japan and California, it is a veritable floating island made up of visible debris and microparticles of plastic, covering an area of approximately 3.5 million km²: an area six times larger than France !
Most of the time, these are plastic bags, bottles and other single-use packaging that end up in the oceans where they remain in their state for a very long period before partially decomposing.
This is a disaster for many species that end up swallowing the small pieces of plastic.
Regarding other sources of marine pollution, oil spills are among the most dangerous for the marine ecosystem.
Groundings and ship accidents are the cause of approximately 2 million tonnes of hydrocarbons discharged into the sea each year.
Oil slick formed after the sinking of the oil tanker Erika on December 19, 1999 off the island of Yeu.
© AFP / Emmanuel Pain
Moreover, in coastal areas, only 20% of wastewater is treated.
The rest is discharged into the water without any prior treatment.
In the same way, chemical substances from industry or agriculture (pesticides) are transported by air or rivers and end up in the oceans.
Overfishing
Finally, overfishing poses a serious threat both to the oceans and to human life.
The increase in water temperature causes many species of fish to move closer to the poles.
About 120 million tons of fish are caught every year in the world, but this quantity has been constantly decreasing for 10 years.
We are already witnessing a phenomenon of scarcity of wild fish.
Philippe Cury, biologist and research director at the IRD (Research Institute for Development), specifies that in an entire area of the North Atlantic, wild sardines have migrated to other areas giving way to jellyfish.
Such examples of ecosystem imbalance are likely to be more and more frequent.
For humans, less fish and other seafood also means less food available.
More serious consequences could affect developing countries and populations living exclusively from fishing.
Our selection on the subject:
To read :
→ [Infographic] How our plastics end up in the oceans
→ All oceans drowned in plastic
→ Australia: the announced disappearance of the Great Barrier Reef
→ The oceans are acidifying... so what?
→ Global warming: developing island states on the front line
→ Marine pollution: act upstream to reduce plastic waste in the Mediterranean
To listen :
→ Climate: the structure of the ocean is changing
→ Rising waters: "Things are likely to go quite quickly, including on French territory"
→ Africa, Indian Ocean, Pacific: what can COP26 do in the face of rising waters?
→ When the ocean advances…
→ Ocean pollution: is the problem underestimated?
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oceans
Environment
Wildlife
Flora
Pollution
Agriculture and Fishing