The warming of the Mediterranean is speeding up the decline of biodiversity in this basin and harming the health and livelihoods of millions who live along its shores or visit as tourists. Scientists watch with growing concern as this warming reaches levels not seen before. The eastern portion bears the heaviest burden, but experts warn the western part may follow suit, as reported by Phys.org.
From Barcelona to Tel Aviv, researchers observe striking temperature increases of three to five degrees Celsius above typical values for this season. Water temperatures even surpass thirty degrees on some days.
The sea’s plight often goes unnoticed by many, yet it is becoming more urgent. Marine heat waves arise when ocean currents push pockets of warm water into new areas. Like land heat waves, those at sea persist longer, occur more often, and intensify, driven in part by human caused climate change.
Joaquim Garrabou of the Barcelona Institute of Marine Sciences describes the trend as very worrying. He notes that the system is being pushed too far and calls for swift action on climate issues.
Garrabou and colleagues recently published a study on Mediterranean heat waves covering 2015 to 2019. The findings indicate these events are causing mass die-offs among marine life.
About forty to fifty species have been affected, including corals, sponges and various algae, spanning thousands of kilometers of the Mediterranean coastline, according to research featured in Nature Global Change Biology.
In the eastern Mediterranean, waters reach about 31ºC
The situation in the eastern basin is especially dire. Gil Rilov, a marine biologist at Israel’s Oceanographic and Limnological Studies Institute, and one of the paper’s authors, states that waters off Israel, Cyprus, Lebanon and Syria are among the hottest spots in the Mediterranean. Average summer sea temperatures are now consistently above 31°C, making the phenomenon less unusual and more routine.
Rilov adds that the rising temperatures push many native species toward the brink because their optimal ranges are exceeded each summer.
What he and his team have observed suggests a broader pattern of biodiversity loss. They predict that warming will spread further west in coming years toward Greece, Italy and Spain.
Garrabou emphasizes the ocean’s role as a major heat sink, absorbing about 90% of excess heat from the planet and around 30% of atmospheric carbon dioxide from fossil fuel use. This carbon sink function helps shield the climate from even more severe impacts.
He warns that this positive effect only holds when oceans are in a healthy condition. Today, he says, the seas are increasingly unhealthy and dysfunctional.
Reducing greenhouse gas emissions remains essential to slowing ocean warming. Meanwhile oceanographers urge authorities to protect 30% of marine areas from harmful human activities such as fishing to support recovery and development.
Currently, merely 8% of the Mediterranean region enjoys some form of legal protection. Yet legal protection does not always ensure effective conservation.
Garrabou and Rilov say politicians often overlook the warming and its consequences in the Mediterranean. They stress that scientists must bring the issue to political decision makers so it can be addressed seriously.
Terrestrial and marine heat waves reinforce one another
Heat waves arise when hot, dry conditions persist with little rain or wind. Terrestrial heat waves can provoke marine heat waves, and the two phenomena feed a dangerous warming cycle.
In many Mediterranean countries, land heat waves have become common, bringing secondary harms such as wildfires, drought, crop losses and record high temperatures.
Experts warn that unchecked maritime heat waves could have serious consequences for nations along the sea, for the millions who spend summers there, and for the more than 500 million people who call the region home. Fish stocks could fall, tourism could suffer as storms intensify on land.
The Mediterranean Sea holds a crucial share of marine diversity
The basin hosts a significant portion of the world’s marine biodiversity, with estimates ranging from four to eighteen percent of known species, while occupying less than one percent of the global ocean surface.
Species essential to ecosystem function, such as the seagrass Posidonia and coral reefs, play a major role in carbon storage and habitat provision, and they face elevated risk.
Researchers note that mortality events have been observed from the surface down to depths of about forty-five meters, with heat waves affecting well over ninety percent of the Mediterranean’s surface.
Temperature rise in the sea continues
Latest scientific articles show the Mediterranean Sea surface temperature rose by about 0.4°C per decade from 1982 to 2018 and has continued to trend upward in the last decade, with no clear signs of reversal.
Experts warn that even small increases can trigger damaging shifts in ocean health. The study indicates affected areas have expanded since the 1980s, covering a larger portion of the Mediterranean.
Garrabou concludes that while biodiversity may adapt to survive, the path we are on could leave human communities without a viable home if not addressed.
This article draws on research reported by Phys.org and aims to reflect the broader scientific consensus on the Mediterranean’s warming crisis.
The content reflects ongoing scientific discourse and emphasizes the urgency of policy action to protect marine and coastal systems for future generations.