Climate change gets in the way of French oyster culture

Crates of oysters during their maturing process in an oyster bed in Marennes along the Seudre river, southwestern France. [Christophe Archambault/AFP]

Rising sea temperatures due to climate change are forcing oyster farmers in France’s southwest to take a break from summer maturation, traditionally a key step in the production of the tasty molluscs.

Starting next year, producers in Marennes Oleron, France’s biggest oyster bay, will no longer be able to steep oysters in shallow clay beds in salt marshes, known as “claires”, during the summer months.

Oyster farmers in this region traditionally keep the molluscs in the oyster beds for the final weeks before their sale. The treatment gives them a less salty and iodic taste than if they come straight from the sea, and earns them the “fine” label, recognised by the EU’s protected geographical indication (PGI) category.

But climate change is negating the effects of the oyster beds.

Scientists have found that because of fast-evaporating water, the salt concentration has become too high between early June and late August, leading to the ban during those months.

Human consumption of oysters goes back thousands of years. They come in a wide variety of flavours and textures depending on water salinity, alkalinity, mineral content and nutrition.

“We’re going to have to accept change,” said Henry Schaller, a local farmer using the claire method for which the Marennes Oleron oyster region is famous.

But the 37-year-old, in the business since 2010, said he had already cut down on summer maturation even before the new rule.

“The oysters had become too salty,” he said. “We had a weaker, lower-quality product.”

The water temperature in the clay oyster beds, filled with sea water thanks to the tides and rhythm of the ocean, can now reach 35 degrees Celsius (95 degrees Fahrenheit) in the summer months, well above the comfort zone of 32C (89.6F) for oysters, which cannot regulate their temperature. [Christophe Archambault/AFP]

This puts them more on the 'front line' of climate change suffering than ocean mammals or fish, said Fabrice Pernet, a scientist at the Ifremer oceanic research centre. 'There is as much reason for concern for oysters as there is for corals. Their fragility is similar,' he said. [Christophe Archambault/AFP]

A farmer drops crates of oysters in oyster beds for maturing in Marennes along the Seudre river, southwestern France. [Christophe Archambault/AFP]

Producers in Marennes Oleron sell up to 60,000 tonnes of oysters per year, of which 17,000 tonnes are of the 'fine' variety. [Christophe Archambault/AFP]

The manager of the Chiron oyster-farming company, Laurent Chiron, holding a basket of Marennes Oleron oysters in L'Eguille, along the Seudre river. [Christophe Archambault/AFP]

'We noticed, because of a changing climate, that the maturation could no longer be carried out in the same way,' said Laurent Chiron, president of the GQHMO association that awards the industry's quality label. [Christophe Archambault/AFP]

According to the new rules, farmers are encouraged to go beyond the traditional winter and summer methods for oyster bed maturation, adopting a more flexible approach. [Christophe Archambault/AFP]

'We are telling oyster farmers, based on how you perceive the climate, you can operate one maturation method or another,' Chiron said. [Christophe Archambault/AFP]

Philippe Morandeau, president of the oyster industry committee in Poitou-Charentes, which includes Charente-Maritime, said he believed any impact on sales figures would be small, given that most oysters are sold for end-of-year festivities when ocean temperatures are low. [Christophe Archambault/AFP]

An employee rinsing oysters ahead of their packaging in baskets at the Chiron oyster-farming company. [Christophe Archambault/AFP]