[LUM#2] Heatwave in the Mediterranean

[LUM Magazine] - Published on April 5, 2016 in Science-Society

For climate specialists, the time for speculation is over: change is here. And the consequences for the regional landscape are already clearly visible.

1.5 degrees. That is the temperature increase that the COP21 agreement aims to keep below. The goal is to limit the damage, because it is clear that we cannot ask for more. And for good reason: "The consequences of global warming are no longer a thing of the future, they are here, right before our eyes," confirms Eric Servat. This is particularly true in the region: "The Mediterranean basin is a hotspot for climate change," says the director of the Research Environment Research Observatory.

"The number of rainy days per year is decreasing. In 2015, there was a long period of almost total drought between early June and mid-August," says Eric Servat. A scorching summer, typical of the Mediterranean. And often followed by a torrential autumn: "In autumn 2014, for example, there were no fewer than nine significant weather events in Languedoc-Roussillon," says the hydrologist. To sum up: increasingly hot and dry summers, followed by torrential rain from September onwards. A typically Mediterranean climate, it would seem. The problem is that it is becoming more and more pronounced. With extreme events set to become increasingly frequent, if researchers' predictions are to be believed.

As a result of these climatic upheavals, ecosystems are changing at the speed of a raging torrent. And the species that inhabit them are forced to adapt, or risk extinction. In Montpellier, researchers are assessing the impact of these changes on flora and fauna. They are also sketching out the new contours of a biodiversity map that is currently being redrawn.

Migratory trees

Although firmly rooted, trees are beginning to migrate like birds. "Mediterranean species will move northward and climb to higher altitudes," predicts Isabelle Chuine of the Center for Functional and Evolutionary Ecology, head of the Seasons Observatory. Some species, such as the holm oak, have already begun this slow migration. "It is estimated that it will find a favorable climate by 2050... but far to the north of the Mediterranean," says the ecologist. And for those that do not move, a new wardrobe is needed to cope with the heat. "The oak trees in the Puéchabon forest, 30 km from Montpellier, have reduced their number of leaves in recent years," says Isabelle Chuine. "This is a way for them to sweat less and need less water."

Vines in danger

It is the most beautiful wild vineyard in France: around a hundred vines clinging to the foothills of Pic Saint-Loup. A heritage that is now in danger: "For the past two years, some vines have been growing poorly, suffering from a lack of water and their foliage has been burned by the sun's rays," laments Jean-Frédéric Terral of the Institute of Evolutionary Sciences in Montpellier. With these few vines, the ancestor of all the world's grape varieties is in danger of disappearing. And its domestic descendants are no more vigorous. "Some grape varieties planted in the region are reaching the limits of their climatic requirements," says the specialist. These are bad times for Merlot in particular, an early-ripening variety that does not cope well with heat waves. " If it is too hot, its entire cycle is affected, from flowering to fruiting. In addition, harvests are starting earlier and earlier, the grapes are of poorer quality, and the alcohol content of the wines is increasing, which is not the desired outcome," explains Jean-Frédéric Terral. As a result , winegrowers will probably have to pull up their Merlot vines and replace them with grape varieties that thrive in the sun.

When baby chickadees appear too early

Great tits and Mediterranean blue tits are traditionally very busy when spring arrives. The family has grown and they have to feed their little chicks, who start chirping as soon as they hatch. On the menu for these first meals is a delicacy: the caterpillars that swarm on the young oak leaves. But with global warming, these leaves are appearing earlier and earlier in the year, and the young chickadees risk missing out on the feast. "For now, the chickadees have found a solution: in half a century, they have moved their egg-laying date forward by two weeks to be in sync with their food source, "explains Anne Charmantier of the Center for Functional and Evolutionary Ecology. "But if global warming becomes too intense, they will not be able to move their egg-laying date forward enough," she warns. And their chicks could well end up empty-beaked...

Fish facing expulsion

And in the water, too, things are heating up. "The Gulf of Lion is one of the coldest regions in the Mediterranean, so it serves as a refuge for fish species that do not tolerate heat well, such as sprat," explains Pierre-Alexandre Gagnaire of the Institute of Evolutionary Sciences in Montpellier. The problem is that these waters are getting warmer."In the Atlantic, fish can swim north to stay cool, but in the Mediterranean, they quickly find themselves trapped,"says the specialist. Mediterranean sprat populations are therefore at risk of melting like snow in the sun."Conversely, other species are appearing, such as the flute fish and the rabbit fish, which have made the journey from the Red Sea via the Suez Canal." And on arrival, they find the warm water they like.

Keywords: Biodiversity, Climate, LUM#2, LUM Magazine, Global warming