In their article discussing the impacts of farm animal production on climate change, Koneswaran and Nierenberg (2008) called for "immediate and far-reaching changes in current animal agriculture practices" to mitigate greenhouse gas (GHG) emissions. One of their recommendations was to switch to organic livestock production, stating that raising cattle for beef organically on grass, in contrast to fattening confined cattle on concentrated feed, may emit 40% less GHGs and consume 85% less energy than conventionally produced beef.

The development of antibiotic resistance in bacteria has been attributed to the overuse of antimicrobials in human medicine. Another route by which humans are exposed to antibiotics is through the animal foods we eat. In modern agricultural practice, veterinary drugs are being used on a large scale, administered for treating infection or prophylactically to prevent infection.

Your Editorial 'A fresh approach to water' (Nature 452, 253; 2008) points out that the world's looming water crisis is driven by climate change, population growth and economic development. In China, changing food-consumption patterns are the main cause of the worsening water scarcity. If other developing countries follow China's trend towards protein-rich Western diets, the global water shortage will become still more severe. (Correspondence)

Animals reared in natural, outdoor conditions without nasty modern drugs yield healthier meat, right? Not necessarily. Wondwossen Gebreyes and colleagues at Ohio State University in Columbus tested US pigs for antibodies - telltale signs of infection - to pathogens that can also affect humans. They found traces of Salmonella in 39 per cent of pigs raised in standard indoor pens and routinely given antibiotics, but in 54 per cent of organic pigs raised outdoors without the drugs (Foodborne Pathogens and Disease, vol 5, p 199).