Environmental Engineering Reference
In-Depth Information
mates that China lost a total of about 290 Mha of forests, with the loss roughly
split between conversions to farmlands, settlements, and transport networks and
excessive cutting for fuel and timber, most of which could have been prevented
with proper management. The most comprehensive reconstruction based on archival
sources goes back only to 1700 (He et al. 2007), when China had nearly 250 Mha
of forests. Extensive deforestation reduced the total to about 160 Mha by 1900 and
to 109 Mha (about 11% of the country's area) in 1949, the year of the establish-
ment of the Communist state.
Quantii cations of preindustrial deforestation are difi cult even for Europe, with
its centuries of often detailed land-use records. The greatest period of the medieval
European forest clearing—what the French historians have called
l'âge des grands
défrichements
(Bloch 1931)—took place between 950 and 1350, after which conver-
sions slowed down for nearly two centuries (a result of epidemic population loss
and slow population growth) before a faster wave of deforestation began during
the early modern age, helped by a rising productivity associated with water-powered
saws that could process cut timber i rst 10 and eventually 30 times faster than
manual cutting with pit saws (Williams 2006).
One of the best-known attempts to capture the spatial dimension of this process
is Otto Schlüter's (1952) reconstruction of forest cover in Central Europe (in this
instance an area extending from Alsace to eastern Poland and from the shores of
the Baltic and the North Sea to the Alps) around the year 900, contrasted with the
well-mapped extent of forests in the same area in 1900. This study, based on a variety
of linguistic evidence (place-names denoting deforestations), archaeological i ndings,
and soil and vegetation history, concluded that about 70% of this large region was
forested in the early medieval period, compared to no more than 25% by 1900.
Richards (1990) estimated that 180 Mha of temperate forest were cleared in Eurasia
and North America between 1700 and 1850 and another 130 Mha between 1850
and 1920, with Russia accounting for nearly half of the 1700-1920 total. Nearly
120 Mha of forests were cleared in the United States between 1630 (when the total
stood at 423 Mha, or 46% of all land, with about 38% in the West) and 1907, when
307 Mha remained, with just over half in the West (USDA 2001).
During the twentieth century the total barely changed, dipping to 299 Mha by
1987 before moving slightly up to 302 Mha by 1997, which means that some 70%
of the area that existed in 1630 is still (or again) covered by forests. As coal replaced
wood as household fuel, the rates of deforestation declined in both Europe and
North America. In contrast, the exploitation of tropical forests accelerated, reaching
unprecedented rates during the last quarter of the twentieth century in West Africa
