[LUM#2] Hot weather on 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. This is the temperature rise that the COP21 agreement aims to avoid. The aim is to limit the damage. Because we understand that we can't ask for more. And with good reason: " The consequences of global warming are no longer in the future, they're here, right before our eyes ", confirms Eric Servat. Particularly in the region: " the Mediterranean basin is a climate change hotspot", explains the director of the Observatoire de Research Méditerranéen de l'Environnement.

" The number of rainy days in the year is decreasing, and in 2015 there was a long period of almost absolute drought between the beginning of June and mid-August," emphasizes 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 9 major climatic events in Languedoc-Roussillon ", says the hydrologist. To sum up: increasingly hot and dry summers, followed by torrential downpours from September onwards. A typically Mediterranean temperament, it seems. Problem: it's getting worse all the time. With extreme events set to become increasingly frequent, if we are to believe the researchers' predictions.

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

Migratory trees

Firmly planted on their roots, trees are beginning to migrate like birds. " Mediterranean species will move northwards and climb in altitude," predicts Isabelle Chuine, from the Centre d'écologie fonctionnelle et évolutive, in charge of the Observatoire des saisons. Some species, such as the holm oak, have already begun this slow migration. " We estimate that it will find a favorable climate by 2050... but very far north of the Mediterranean," explains the ecologist. And for those who don't move, a new wardrobe is needed to cope with the heat. The oaks in the Puéchabon forest, 30 km from Montpellier, have reduced their number of leaves in recent years," says Isabelle Chuine. It's a way for them to sweat less and need smaller quantities of water.

Vines in peril

It's the most beautiful wild vineyard in France: a hundred or so vines clinging to the foothills of the Pic Saint-Loup. A heritage now in danger: " for the past 2 years, some vines have been developing poorly, suffering from a lack of water and their foliage is burnt by the sun's rays ", laments Jean-Frédéric Terral of Montpellier's Institut des sciences de l'évolution. With these few vines, the ancestor of all the world's grape varieties is in danger of disappearing. And its domesticated descendants are no more dashing. " Certain grape varieties planted in the region are reaching the limits of their climatic requirements ", stresses the specialist. This is particularly true of Merlot, an early-ripening grape that doesn't cope well with the heatwave. " If the weather is too hot, its entire cycle is affected, from flowering to fruiting. What's more, as harvesting gets earlier and earlier, the grapes are of poorer quality and the alcohol content of the wines increases, which is not what we're aiming for," explains Jean-Frédéric Terral. As a result, winegrowers will probably have to uproot their Merlot vines and replace them with more sun-loving varieties.

When baby chickadees appear too early

Mediterranean great tits and blue tits are traditionally very busy when spring arrives. The family has grown, and they're busy pecking at little chicks who, as soon as their shells are cracked, start squealing like crazy. On the menu for these first meals is a delicacy of choice: caterpillars, which swarm as young oak leaves sprout. But with global warming, these caterpillars are appearing earlier and earlier in the year, and the young chickadees are in danger of missing out on the feast. " For the time being, tits have found a solution: in half a century, they have brought their egg-laying date forward by 2 weeks to match their food resources ," explains Anne Charmantier of the Centre d'écologie fonctionnelle et évolutive. " But if global warming becomes too intense, they won't be able to advance their laying date sufficiently," she warns. And their chicks could well end up with their beaks in the water...

Fish on the move

And in the water too, things are heating up. " The Gulf of Lion is one of the coldest regions in the Mediterranean, so it's a refuge for fish species that don't do well in the heat, such as sprat," explains Pierre-Alexandre Gagnaire of Montpellier's Institut des Sciences de l'évolution. The problem is that these cold waters are less and less so. " In the Atlantic, fish can swim northwards to stay cool, but in the Mediterranean they quickly find themselves stuck ," explains the specialist. Mediterranean sprat populations are therefore likely to melt like snow in the sun. "On the other hand, other species are making their appearance, such as flounderfish and rabbitfish, which have made the journey from the Red Sea via the Suez Canal. And when they arrive, they'll find the warm water they love.

Key words : Biodiversity, Climate, LUM#2, LUM Magazine, Global warming