Scientists are warning of dire consequences as the Mediterranean heats up

MADRID (AP) — While vacationers may be basking in the Mediterranean’s summer heat, climate scientists are warning of dire consequences for its marine life as it scorches in a series of intense heatwaves.

From Barcelona to Tel Aviv, scientists say they are witnessing extraordinary temperature increases ranging from 3 degrees Celsius (5.4 Fahrenheit) to 5 degrees Celsius (9 Fahrenheit) above the norm for this time of year. Water temperatures have regularly exceeded 30 C (86 F) on some days.

Extreme heat in Europe and other countries around the Mediterranean has made headlines this summer, but rising sea temperatures have largely been out of sight.

Marine heat waves are caused by ocean currents that create areas of warm water. Weather systems and heat in the atmosphere can also build up in degrees relative to 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 Institute of Marine Sciences in Barcelona. “We are pushing the system too far. We need 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 says these phenomena have led to “mass mortality” of marine species.

About 50 species, including corals, sponges and algae, were affected along thousands of kilometers of Mediterranean coastline, according to the study, which was published in the journal Global Change Biology.

The situation in the eastern Mediterranean basin is particularly tragic.

The waters off Israel, Cyprus, Lebanon and Syria are “the hottest spot in the Mediterranean, for sure,” said Gil Rilov, a marine biologist at Israel’s Institute of Oceanographic and Limnological Research and one of the paper’s co-authors. . Average summer sea temperatures are now consistently above 31 C (88 F).

Those warming seas are driving many native species to the brink, “because every summer their temperature optimum is exceeded,” he said.

What he and his colleagues see 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 serve the planet by absorbing 90% of the earth’s excess heat and 30% of the carbon dioxide emitted into the atmosphere by coal, oil and natural gas production. This carbon sink protects the planet from even harsher climate impacts.

This was possible because the oceans and seas were in a healthy state, Garrabou said.

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

While the Earth’s greenhouse gas emissions will have to be drastically reduced if sea warming is to be contained, ocean scientists are looking for specific principles to guarantee that 30% of marine areas are protected from human activities such as fishing, which would give the species a chance to recover and thrive.

About 8% of the Mediterranean area is protected today.

Garabu and Riloff said policymakers are largely unaware of Mediterranean warming and its impact.

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

Heat waves occur when particularly hot weather continues for a set number of days, with no rain or little wind. Land heat waves help trigger marine heat waves, and the two tend to feed off each other in a vicious heat cycle.

Dry heat waves have become common in many countries around the Mediterranean, with dramatic side effects such as wildfires, droughts, crop losses and sweltering temperatures.

But sea heat could also have serious consequences for countries bordering the Mediterranean and the more than 500 million people who live there if not addressed soon, scientists say. Fish stocks will be depleted and tourism will be adversely affected as destructive storms could become more frequent 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 function and diversity of marine habitats. Species such as Posidonia oceanica seagrasses, which can absorb huge amounts of carbon dioxide and protect marine life, or coral reefs, which also host wildlife, will be at risk.

Garrabou says the mortality effects on species were observed between the surface and a depth of 45 meters (about 150 feet), where recorded marine heat waves were extreme. Heat waves affected more than 90% of the surface of the Mediterranean.

According to the latest scientific work, the sea surface temperature in the Mediterranean increased by 0.4 C (0.72 F) every decade between 1982 and 2018. On an annual basis, it increases by about 0.05 C (0.09 F) the past decade with no sign of letting up.

Even fractions of a degree can have devastating effects on ocean health, experts say.

Affected areas have also increased since the 1980s and now cover most of the Mediterranean, the study suggests.

“The question is not about 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, the people, will have nowhere to live.”


Ilan Ben Zion reported from Jerusalem.


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