EMBARGOED TO 0001 SATURDAY NOVEMBER 6 File photo dated 15/10/21 of shoppers in the fruit and vegetables section of a branch of Sainsbury's in London. The bosses of five of the UK's biggest supermarkets have promised to halve the environmental impact of a weekly food shop by the end of this decade, as leaders meet in Glasgow at a key climate change summit. Chief executives from Tesco, Sainsbury's, Waitrose, Co-op and M&S said they would work with the World Wide Fund for Nature (WWF) to reduce natural destruction. Under a pledge they will halve the amount of global warming that shopping baskets cause, the forests that are cut down to fill the baskets, the impact of the agriculture and seafood in baskets, and the food waste and packaging they produce.