Global gross primary GPP productivity data

Since its inception c. 12,000 years ago (Section 5.2), agriculture has been introduced to all but the most inhospitable regions and has been the most important aspect of hmnan activity in the transformation of the Earth s biomes. Some of this transformation has been subtle, involving the manipulation of components of natural ecosystems such as stock rearing in semi deserts, while other types of transformation have involved complete replacement of vegetation cover with pasture or cultivated crops. Transformations of both kinds have occurred over many millennia, as 

These data show that immediate post-1700 cropland expansion in Emope and China probably continues an aheady established growth trend, while the Former Soviet Union, tropical Africa and South Asia experienced a significant but less extensive pulse of cropland creation between 1700 and 1850. This was a take off time for many parts of the world, especially in the eastern part of North America. By 1900 croplands were expanding in the west of North America, Central America, and South America and Australia. Overall, croplands expanded from c. 4.05 x 10 km in 1700 to 17.92 x 10 km in 1990, an increase of c. 342 percent. 

Measures of the alteration of the natural environment are examined in Section 6.4. As a carbon processing system, agriculture is, self evidently, 

I I Divaniliad iFopicBl and siArbopical crops I I Dairy, Livestock 

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Table 6.4. Global gross primary (GPP) productivity data (from Field et al. 1998).

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