As world population continues to increase, the remaining area of uncultivated land suitable for agricultural production of food and fibre is decreasing. While this is generally true, there are significant regional differences such that in developed countries, the area of uncultivated land available for cropping is very limited, while the ‘expansion of arable land continues to be an important source of agricultural growth in sub-Saharan Africa, South America and East Asia, excluding China’ (FAO, 2003b). Similarly, the volume of freshwater that can be used or harvested for agricultural production is increasingly limited in many regions because of competition for this critical resource.