I've noticed more people collecting blackberries this year, and a few of them had bikes. Perhaps it's the recession. There are lots of things which could be harvested free without any significant environmental effects such as rose hips (rose hip syrup) and elderflower (not the berries) which makes a refreshing drink.
Eating grey squirrel would be a great environmental initiative as they have driven our native red squirrel almost to extinction and they eat birds' eggs and fleshlings.
Some restaurants serve them.
For similar reasons I would also extent our diet to include cats.
I thought the definition of sustainability went along the following lines "we don't do anything to meet our needs which compromises the ability of future generations to meet their needs."
Quite woolly I agree but that's intrinsic to the concept.
I've never understood why we eat cows, sheep, goats, chickens and rabbits but not horses, cats and dogs. I suppose it's a cultural thing.
I'd quite happily eat the neighbour's dog if it stopped it from barking.