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the estimate of "rain-fed cultivation potential" taken from the Global Agro-Ecological Zone (GAEZ) work of Fischer et al. (2000, Table 35). This potential land can be expanded through technological means, such as irrigation and greenhouse production. However, greenhouse production carries high energy costs and is therefore only suitable for producing high-value crops (a good example is Marijuana, but also flowers and vegetables), whereas irrigation is limited by the amount of water available. Therefore, the total amount of suitable rainfed cropland is a good measure for this preliminary analysis. Comparing the area of cropland in 2005 to the total potential (Figure 2.6), it is clear that most of the remaining cultivable land is in Africa or South America. It is also evident that Asia has used up almost all of its cultivation potential. While there is still cultivation potential in Africa and South America, much of that potential land is currently occupied by forests, which implies continued loss of valuable forests if we exploit that land. Moreover, currently prime farmland is already being lost rapidly to degradation and urbanization, and there is even more pressure from biofuel crops (Righelato and Spracklen 2007; Sorensen et al. 1997; Wood et al. 2000). Clearly, future expansion of food production will need to occur through intensification of food production, rather than cropland expansion, as has been the case for the last fifty years (see next section).

Nonetheless, at current rates of change (over the 1990-2005 period), we can estimate the numbers of years that are left of suitable cropland or forest land before this resource is exhausted (Table 2.1). Asia has little suitable cropland left, while Africa has almost 300 years of potential expansion at current rates. Current deforestation rates are threatening the forests of Africa and South America. However, these regional numbers mask critical variations within each region. For example, while deforestation in Asia looks nonthreat-ening, this is mainly the result of the vast increase in forests in China masking

□ 2005 ■ Remaining suitable cropland

□ 2005 ■ Remaining suitable cropland

Africa Asia Europe North America Oceania South America

Figure 2.6 Potential cultivable area that remains in different regions of the world. Africa and South America have the most land suitable for cultivation; Asia the least.

Africa Asia Europe North America Oceania South America

Figure 2.6 Potential cultivable area that remains in different regions of the world. Africa and South America have the most land suitable for cultivation; Asia the least.

rapid deforestation elsewhere. A national-level analysis could reveal some of these nuances. Unfortunately, national-level data on suitable cropland area are not readily available, but they are for forests. Of those countries having more than 1% of the world's total forests, Indonesia is losing forests most rapidly (47 years left), followed by Zambia (95 years) and Sudan (114 years). Brazil, with 12% of the world's forests, has 170 years of forest left at current rates of deforestation.

An additional caveat to add to this analysis is that global environmental changes may alter the availability of cropland or forestland in the future. For example, Fischer et al. (2002) and Ramankutty et al. (2002) have shown that changes in climate predicted for the end of the 21st century would result in increases in cropland suitability in the high-latitude regions of the Northern Hemisphere (mostly occupied by developed nations), while suitability is likely to decreases in the tropical regions (mostly developing nations). Sea-level rise is an additional threat to croplands in some regions (e.g., Bangladesh), although the vast majority of the world's croplands are located in the continental interior.

Who Owns the Land?

Thus far we have looked at the global distribution of land: how it is changing, and where the limits are. Now we turn to the question: Is the current distribution of land equitable? Given the increasing amount of global trade, it hardly matters anymore whether one has all the resources needed within one's own nation-state. Still, given the recent emphasis in some developed nations on "energy independence" (related to energy security), it is clear that "land resource independence" may be important to consider.

How are global cropland and forest resources distributed around the world, relative to where people live? Referring to Table 2.2, we see that in 2005, the global average per-capita cropland area was 2400 m2/person, down from 2900 m2/person in 1990. North America and Oceania had more than twice the global average, while Asia was the most impoverished, with only 1400 m2 of cropland

Table 2.1 Estimated number of years of suitable cropland and forest land remaining, given the rates of land conversion over 1990-2005. Where values are not shown, cropland areas are decreasing, or forest areas are increasing.

Number of years remaining: Cropland Forest

Table 2.1 Estimated number of years of suitable cropland and forest land remaining, given the rates of land conversion over 1990-2005. Where values are not shown, cropland areas are decreasing, or forest areas are increasing.

Number of years remaining: Cropland Forest

Africa

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