Multiples are being urged to stop buying illegally produced strawberries from Spain.
WWF campaigners have warned that irrigation by unlicensed farmers in the Huelva region has lowered the water table in the protected Donana Marshes by up to 20m. This is drying watercourses, shrinking marshes and decimating populatons of Iberian Lynx, otter, Egyption mongoose and the genet.
"Illegal strawberry farms account for about 50% of the region's production," said WWF Spain's Guido Schmidt. "Of the 6,000 hectares, we estimate 2,100 hectares are illegal."
WWF said 1,700 boreholes were being used to irrigate the strawberry crop, of which 700 have not been approved. "There is probably no-one in Donana who is 100% legal," Schmidt said.
British supermarkets buy much of the region's crop to extend the home season, and WWF is asking them to make sure their suppliers have the necessary permits. Schmidt claimed some British chains only paid lip service to the paperwork.
The pressure has paid off in the Netherlands and Switzerland, where multiples have tried to legalise their Spanish suppliers. The Albert Heijn chain is attaching a leaflet about protecting the marshes to all strawberries.
Schmidt said he wanted to work with the multiples. "People want out-of-season products and strawberry farming is economically important, so we're not calling for a boycott."
But in the UK, WWF is reluctant to focus too much attention on the problem because it is drawing up a wider strategy on water use. Campaigner Stuart Orr said: "It's an issue that relates to most of the crops grown in Almeria where aquifer use is past sustainable levels. Supermarkets must engage their suppliers on this."
Tesco's Nature's Choice protocol doesn't mention sustainable water sourcing or soil degradation, Orr said. Tesco and Sainsbury's said they only sourced from legal farms in Huelva.