Is there really spare land? A critique of estimates of available cultivable land in developing countries

Five assessments covering less-developed countries have identified a 'land balance', available for future cultivation, using the approach of inventory and difference: assessment of the area cultivable, and subtraction of the area presently cultivated. All arrive at a balance of 1600-1900 Mha, about twice the present cultivated area. The supposed existence of this spare land is widely quoted in forecasts of capacity to meet the food requirements for future population increase. It is argued here that these estimates greatly exaggerate the land available, by over-estimating cultivable land, under-estimating present cultivation, and failing to take sufficient account of other essential uses for land. Personal observation suggests that the true remaining balance of cultivable land is very much smaller, in some regions virtually zero. An order-of-magnitude estimate reaches the conclusion that in a representative area with an estimated 'land balance' of 50%, the realistic area is some 3-25% of the cultivable land. This speculation could be tested by directly attempting to find such land in areas where it is supposed to exist. The impression given by current estimates, that a reserve of spare land exists, is misleading to world leaders and policy-makers.