Environmental Engineering Reference
In-Depth Information
India's farmland expanded by about 40% during the twentieth century, with major
gains in the northwest (Punjab) and the northeast (Assam). The best reconstruction
of China's land-use changes shows a gain of more than 25% (30 Mha) between
1900 and 1980, from 113 to 143 Mha, mostly through grassland and wetland
conversions in the northeast (Huang et al. 2010) and forest conversions in the
southwest—followed by a loss of more than 5% between 1980 and 2005 (Liu and
Tian 2010).
Unmistakable signs of saturation and stagnation, in some cases followed by
substantial retreats, were most noticeable during the second half of the twentieth
century in Europe. Between 1950 and 2000 the total farmland area hardly changed
in the three largest agricultural producers, France, Germany, and Spain, and declined
by 20% in the UK, by 23% in Italy, and by 25% in Sweden. Abandonment of
cropland following the demise of the USSR was on a scale large enough (more than
200,000 km
2
) to make a measurable difference to the global carbon balance: Vuich-
ard et al. (2008) calculated that the land recovered by herbaceous plants increased
the annual storage of carbon by nearly 500 kg C/ha, or by a total on the order of
10 Mt C.
In contrast, the twentieth century's greatest expansion of farmland took place in
Brazil, where the farmland increased tenfold between 1900 and 1950, and that total
then more than tripled by the year 2000. Most of these gains took place after the
mid-1960s in
cerrado
, vast grassland with poor soils (made productive by appropri-
ate fertilization) but that with adequate rainfall has become the country's largest
beef- and soybean-producing area, and conversions to cropland and pastures have
also encroached on the Amazonian rain forest, with major losses in the states of
Rondônia, Mato Grosso, and Tocantins (Tollefson 2010).
In absolute terms, Brazil's post-1960 expansion of pastures has no parallel world-
wide, but the land devoted to grazing has also seen major global gains since the
beginning of the early modern era, for two main reasons. First, faster population
growth that began during the early modern era has been pushing increasing numbers
of pastoralists into less inviting areas where grazing requires more land for a unit
of annual meat or milk productivity. Second, the extension of large-scale commercial
cattle production onto the vast grasslands of North America and Australia during
the second half of the nineteenth century and onto the South American and African
grasslands throughout most the twentieth century added nearly twice as much pas-
tureland in 200 years as the total arable land accumulated after some ten millennia
of settled cultivation, but without any expansion of true pastoralist populations.
Approximate estimates of the world's grazing land show a slow growth during the
