In its eastern part, the water is always at 31ºC and the Spanish coasts could follow the same path
The warming of the Mediterranean waters it is accelerating the degradation of the biodiversity of this basin, but it also poses a threat to the well-being of the millions of residents and tourists who live on its shores. Scientists are watching with great concern how this warming is reaching levels unimaginable until recently. The eastern part bears the brunt, but the western part may end up following the same path, according to an article published on Phys.org.
From Barcelona to Tel Aviv, scientists are witnessing exceptional temperature rises ranging from 3 to 5 degrees Celsius above normal for this time of year. The water temperature has even exceeded 30 C on some days.
At sea, the situation goes more unnoticed by most people, but the situation is beginning to be alarming. Marine heat waves are caused by ocean currents that accumulate areas of warm water. Y like their terrestrial counterparts, marine heat waves are longer, more frequent and more intense due to human-induced climate change.
The situation is “very worrying”, says Joaquim Garrabou, a researcher at the Barcelona Institute of Marine Sciences. “We are taking the system too far. We have to take action on climate issues as soon as possible.”
Garrabou is part of a team that recently published the report on heat waves in the Mediterranean Sea between 2015 and 2019. The report states that these phenomena have caused a “mass mortality” of marine species.
Some 50 species, including corals, sponges and algae, were affected along thousands of kilometers of Mediterranean coasts, according to the study, which was published in the journal Global Change Biology.
Waters at 31ºC in the eastern Mediterranean
The situation in the eastern Mediterranean basin is particularly serious. The waters off Israel, Cyprus, Lebanon and Syria are “the hottest spot in the Mediterranean, without a doubt,” said Gil Rilov, a marine biologist at Israel’s Institute for Oceanographic and Limnological Research, and one of the paper’s co-authors. Average summer sea temperatures are now consistently above 31 C; that is to say, it is not something exceptional, but habitual.
These increasingly warmer seas are pushing many native species to the brink, “because every summer their optimum temperature is exceeded,” he said.
What he and his colleagues are witnessing in terms of biodiversity loss is what is predicted to happen further west in the Mediterranean towards Greece, Italy and Spain in the coming years.
Garrabou points out that the seas have been serving the planet by absorbing 90% of the excess heat from the earth and 30% of the carbon dioxide emitted into the atmosphere from the production of coal, oil and gas. This carbon sink effect protects the planet from even more severe climate effects.
This beneficial effect has been possible because the oceans and seas were in healthy conditions, explains Garrabou. “But now we have brought the ocean to an unhealthy and dysfunctional state,” he warns.
While the Earth’s greenhouse gas emissions will have to be drastically reduced if ocean warming is to be reduced, oceanographers are specifically looking for authorities to ensure that 30% of marine areas are protected from human activities such as fishing, which that would give the species a chance to recover and thrive.
Currently, only 8% of the Mediterranean Sea area is protected under some legal figure, but this does not always mean that in these areas there is an effective preservation of their resources.
Garrabou and Rilov believe politicians are largely unaware of Mediterranean warming and its impact. “It’s our job as scientists to bring this situation to their attention so they can think about it,” Rilov said.
Terrestrial and marine heat waves feed each other
Heat waves occur when especially hot weather continues for a set number of days, with no rain or little wind. Terrestrial heat waves help cause marine heat waves, and the two tend to feed off each other in a vicious circle of warming.
Terrestrial heat waves have become common in many Mediterranean countries, with tragic secondary effects such as forest fires, droughts, crop failures and extremely high temperatures.
But marine heatwaves could also have serious consequences for countries bordering the Mediterranean, both for the people who spend the summer there and for the more than 500 million people who live there if it is not fixed soon, scientists say. Fish stocks will be depleted and tourism will be negatively affected as destructive storms could become more common on land.
Despite representing less than 1% of the world’s ocean surface, the Mediterranean is one of the main reservoirs of marine biodiversity, containing between 4% and 18% of the world’s known marine species.
Some of the most affected species are key to maintaining the functioning and diversity of marine habitats. Species such as grasslands Posidonia oceanicawhich can absorb large amounts of carbon dioxide and support marine life, or coral reefs, which also support wildlife, would be at risk.
Garrabou says that the impacts of mortality on species are observed between the surface and 45 meters deep, where recorded marine heat waves were exceptional. Heat waves affected more than 90% of the surface of the Mediterranean Sea.
heating without brake
According to the most recent scientific articles, the sea surface temperature in the Mediterranean has increased by 0.4 C every decade between 1982 and 2018. Annually, it has risen about 0.05 C over the last decade, with no sign of letting up.
Even fractions of degrees can have disastrous effects on the health of the oceans, experts say. Affected areas have also grown since the 1980s and now cover most of the Mediterranean, the study suggests.
“The issue is not the survival of nature, because biodiversity will find a way to survive on the planet & rdquor ;, indicates Garrabou. “The question is if we continue in this direction, maybe our society, humans, don’t have a place to live.”
Reference article: https://phys.org/news/2022-08-fast-warming-ailing-med-sea.html
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