Take food miles. A single flight to New York emits more carbon dioxide than the average car does in a whole year (BBC TV's Know Your Planet Test). How many cars' worth of pollution does it take to fly in the daily supply of baby vegetables and Fairtrade bananas from far-flung climes then? And pity the poor sod who has to plant the 200 trees required to atone for just the New York flight alone.
Planting trees is no simple solution either, because not all trees are equal. Palm tree plantations pose a greater threat to the endangered orangutan than climate change or pollution (palm oil is an ingredient in one in ten products on our supermarket shelves).
Cows are certainly not at risk of extinction. Yet the old gasbags emit more methane than petrol engines, fridges or nuclear reprocessing (says the Beeb). Should we simply eat them all, then?
Alas, we love our organic dairy products too much. If only some clever clogs hadn't put sardines in my milk jug.