Glob. Change Biol. 15, 1716–1726 (2009)

Increased agricultural yields do not necessarily free up land for nature, say Robert Ewers, now at Imperial College London, and his colleagues. Some conservationists have argued that intensive agriculture could result in such 'land sparing', but other forces tend to keep land under the plough.

The researchers analysed changes in yields of the world's 23 most important food crops and in per-capita cropland area for 124 countries between 1979 and 1999. Developing countries showed the strongest link between increased yields and reduced farmland area, but this was largely counteracted by farmers growing cash crops on land no longer needed for staples. No such trend was seen for developed countries — perhaps, the team suggests, because agricultural subsidies mean that land is farmed whether it's needed or not.