From Simon Fairlie
Fred Pearce’s pursuit of the origin of the statistic that invasive species have contributed to 40 per cent of recent extinctions (5 September, p 26) reminded me of my own investigation into another commonly repeated factoid: that 100,000 litres of water are required to produce 1 kilo of beef. After tracing the statistic back through a similar series of academic iterations, it emerged that it takes into account every scrap of precipitation that falls upon the land that a beef cow occupies – even though rain would fall whether the cow were there or not.
Charmouth, Dorset, UK
