Published: 11 February 2008
More than a third of Earth's ice-free land area is now being used for farming. McGill's Navin Ramankutty and colleagues compared agricultural inventories from all countries with satellite land-cover data for the same areas, and wrote a computer program to recognize pasture and crop land. They estimate that 28 million square kilometres (22 per cent) of ice-free land surface is covered in pasture and 15 million square km (12 per cent) is used to grow crops. Their 10-km-resolution maps provide the most detailed and accurate figures to date.