Mark Richards' suggestion in his letter published on the 30th September that we should switch to a vegan diet to save the environment demonstrates a marked ignorance of basic principles of agriculture. Here’s two experiments: first, try living on grass. You can’t, because your body is not adapted to gain enough nutrition from it. Next, try growing food crops on land normally used for pasture. This may be possible…with the use of increased levels of agricultural industrialisation, massive quantities of nitrate fertiliser (having liberated our manure-producing animals, commercially viable organic farming becomes nearly impossible) and the wholesale destruction of ancient hedgerows…oh wait, weren’t we supposed to be saving the environment?