Not sure if you got to the end of the article, but the Tesco people themseves said:
I'm all for gardening and eating local, but it seems to be in the splash compared to big ones like a well insulated house.
I agree...to an extent. But food production is an enormous source of air and water pollution, independent of the GHG issue. And small local farms are much more likely to follow sustainable farming practices than the big boys are. I know that the local growers I buy food from care deeply about their land. They own it, they live and work on it, and they plan to hold it for many years. They also follow a business model that emphasizes direct relationships with their consumers, so they have lots of concerned people keeping an eye on what they do.