Read Monbiot article here. 

Excerpt:

So, perhaps, is the sheer scale of the business. Wal-Mart and Tesco can change the world at the stroke of a pen, but one decision they will not make voluntarily is to relax their grip on local economies. It will always be harder for small businesses to work with a global behemoth than with the local baker or butcher; Tesco's economy will continue to favour the big, distant supplier over the man down the road. And what of the sense of community that independent small shops help to foster, which encourages people to make their friends close to home? If love miles are the most intractable cause of climate change, we need to start cultivating as much community spirit as we can.

But there is a bigger contradiction than this, which has been overlooked by the supermarkets and by many of their critics. "The green movement," Leahy tells us, "must become a mass movement in green consumption." But what about consuming less? Less is the one thing the superstores cannot sell us. As further efficiencies become harder to extract, their growth will eventually outstrip all their reductions in the use of energy. This is not Tesco's problem alone: the green movement's alternatives still lack force.

The big retailers are competing to convince us that they are greener than their rivals, and this should make us glad. But we still need governments, and we still need campaigners.