MADRID (AP) — While vacationers can enjoy the Mediterranean’s summer heat, climate scientists are warning of dire consequences for marine life as it burns up in a series of severe heat waves.
From Barcelona to Tel Aviv, scientists say they are witnessing exceptional 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 are largely out of sight and out of mind.
Sea heat waves are caused by ocean currents that form areas of warm water. Weather systems and heat in the atmosphere can also build up to degrees of the water’s temperature. And like their land-based counterparts, heat waves at sea are longer, more frequent and more intense because of human-induced climate change.
The situation is “very worrying,” said Joaquim Garrabou, a researcher at the Institute of Marine Sciences in Barcelona. “We are pushing the system too far. We must act as soon as possible against the climate problem.”
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 deaths” of marine species.
About 50 species, including corals, sponges and seaweed, were affected along thousands of miles of Mediterranean coasts, according to the study, which was published in the journal Global Change Biology.
The situation in the Eastern Mediterranean is particularly dire.
The waters off Israel, Cyprus, Lebanon and Syria are “certainly the hottest hotspot in the Mediterranean,” said Gil Rilov, a marine biologist with Israel’s Oceanographic and Limnological Research Institute, and one of the co-authors of the study. article. The average sea temperature in summer is now consistently above 31 C (88 F).
These warming seas are pushing many native species to the brink, “because each summer their optimum temperatures are exceeded,” he said.
What he and his colleagues see in terms of biodiversity loss is what is expected to happen further west in the Mediterranean towards Greece, Italy and Spain in the coming years.
Garrabou points out that seas have served the planet by absorbing 90% of the Earth’s excess heat and 30% of the carbon dioxide emitted into the atmosphere by the production of coal, oil and gas. This carbon sink effect protects the planet from even harsher climate effects.
This was possible because oceans and seas were in a healthy state, Garrabou said.
“But now we have driven the ocean to an unhealthy and dysfunctional state,” he said.
While global greenhouse gas emissions will need to be drastically reduced if marine warming is to be contained, ocean scientists are specifically seeking authorities to ensure that 30% of marine areas are protected from human activities such as fishing, which would give species a chance to recover and flourish.
About 8% of the Mediterranean area is currently protected.
Garrabou and Rilov said policymakers are largely unaware of the warming Mediterranean and its impact.
“Our job as scientists is to bring this to their attention so they can think about it,” Rilov said.
Heat waves occur when particularly warm weather lasts for a certain number of days, with no rain or little wind. Heat waves on land help create heat waves at sea, and the two tend to feed each other in a vicious, warming cycle.
Land heat waves have become commonplace in many countries around the Mediterranean, with dramatic side effects such as wildfires, drought, crop losses and unbearably high temperatures.
But heatwaves at sea could also have serious consequences for the Mediterranean countries and the more than 500 million people who live there if not addressed quickly, scientists say. Fish stocks will be depleted and tourism will be adversely affected as devastating storms on land could become more frequent.
Despite representing less than 1% of the global ocean surface, the Mediterranean is one of the most important reservoirs of marine biodiversity, containing between 4% and 18% of the world’s known marine species.
Some of the most affected species are essential to maintaining the functioning and diversity of marine habitats. Species such as the Posidonia oceanica seagrass meadows, which can absorb huge amounts of carbon dioxide and protect marine life, or coral reefs, which are also home to wildlife, would be at risk.
Garrabou says the mortality effects on species were observed between the surface and 45 meters (about 150 feet) deep, where the recorded heat waves at sea were exceptional. Heat waves hit more than 90% of the surface of the Mediterranean Sea.
According to the most recent scientific papers, sea surface temperatures in the Mediterranean Sea have increased by 0.4 C (0.72 F) every decade between 1982 and 2018. past decade without any sign of cessation.
Even fractions of degrees can have disastrous consequences for ocean health, experts say.
The affected areas have also grown 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 whether we continue to move in this direction, maybe our society, people, will not have a place to live.”
Ilan Ben Zion reported from Jerusalem.
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