The rapidly warming and sick Mediterranean Sea may be a sign of things to come

MADRID (AP) — While vacationers can bask in the summer heat of the Mediterranean Sea, climatologists are warning of dire consequences for its marine life as it burns up in a series of severe heat waves.

From Barcelona to Tel Aviv, scientists say they are seeing exceptional temperature rises ranging from 3 degrees Celsius (5.4 Fahrenheit) to 5 degrees Celsius (9 Fahrenheit) above the norm for this time of year. The water temperature has regularly exceeded 30 C (86 F) on some days.

Extreme heat in Europe and other Mediterranean countries has grabbed headlines this summer, but rising sea temperatures are largely out of sight and out of mind.

Marine heat waves are caused by ocean currents that accumulate areas of warm water. Weather systems and heat in the atmosphere can also add degrees to the water temperature. And like their counterparts on land, 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 pushing the system too far. We have to take action on climate problems 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 says that these phenomena have caused “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.

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 of Oceanographic and Limnological Research and one of the paper’s co-authors. Average sea temperatures in the summer are now consistently above 31 C (88 F).

These increasingly warm seas are pushing many native species to the limit, “because every summer they exceed their optimum temperature,” he said.

What he and his colleagues are witnessing in terms of biodiversity loss is what is projected 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 was possible because the oceans and seas were in healthy condition, Garrabou said.

“But now we have brought the ocean to an unhealthy and dysfunctional state,” he said.

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 prosper.

About 8% of the Mediterranean Sea area is currently protected.

Garrabou and Rilov said politicians are largely unaware of the warming Mediterranean and its impact.

“It’s our job as scientists to bring this to their attention so they can think about it,” Rilov said.

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 dramatic secondary effects such as wildfires, droughts, crop failures and extremely high temperatures.

But marine heatwaves could also have dire consequences for countries bordering the Mediterranean and the more than 500 million people who live there if not tackled 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 Posidonia oceanica meadows, which can absorb large amounts of carbon dioxide and support marine life, or coral reefs, which are also home to wildlife, would be at risk.

Garrabou says the impacts of mortality on species were seen between the surface and 45 meters (about 150 feet) deep, where recorded marine heat waves were exceptional. Heat waves affected more than 90% of the surface of the Mediterranean Sea.

According to the most recent scientific articles, the sea surface temperature in the Mediterranean has increased by 0.4 C (0.72 F) every decade between 1982 and 2018. Annually, it has increased by about 0.05 C (0.09 F ) for the past decade without any sign of letting up.

Even fractions of a degree 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,” Garrabou said. “The question is if we continue in this direction, maybe our society, humans, don’t have a place to live.”


Ilan Ben Zion reported from Jerusalem.


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