Environmental Engineering Reference
In-Depth Information
Besides i nding a surprising lack of agreement on the actual extent of the practice
throughout the region, most of these studies document the replacement of shifting
cultivation either by other forms of agriculture or silviculture (rubber or fruit trees,
oil palms, plantation timber), as well as decreases in fallow length (Schmidt-Vogt et
al. 2009). They stress its rationality in many tropical mountain environments, its
suitability for smallholder operations, and, if properly practiced, its relatively high
productivity. Moreover, case studies in Malaysia and Indonesia show that fallow
length is a very weak predictor of subsequent yields and other factors (above all
droughts, l oods, and pests) are much more important (Mertz et al. 2008). Studies
of vegetation recovery in northwestern Vietnam have demonstrated that the effect
on biodiversity may not be as damaging as has been usually thought: after 26 years
a secondary growth had half the species of the old-growth forest, and it was esti-
mated that it would eventually reach a similar plant species diversity and about
80% of the original biomass (Do, Osawa, and Thang 2010).
Generalizations concerning pastoralism—which entails the metabolic conversion
of grassy phytomass into meat, blood, and milk (and also wool and hides) through
animal grazing—and fairly reliable summations of its worldwide claim on biomass
are no less elusive. Pastoralism is perhaps best dei ned as a form of prey conserva-
tion whereby deferred harvests are proi tably repaid by growing stocks of zoomass
(Alvard and Kuznar 2001). This trade-off is more proi table for larger animals, but
it is not surprising that the smaller species, sheep and goats, were domesticated i rst,
because they have higher growth rates and are less risky to manage. The earliest
domesticated animals—leaving dogs aside (Pang et al. 2009)—were sheep: their
domestication process began about 11,000 years ago in Southwest Asia, and it was
followed by goats and cattle (86,000 BCE), and later horses and water buffaloes
(4000 BCE); domesticated pigs have been around nearly as long as sheep, chicken
only about half that time (Ryder 1983; Harris 1996; Chessa et al. 2009).
Agropastoralism eventually became the dominant way of food production through-
out Europe, North Africa, and West and Central Asia. Traditional pastoralist prac-
tices were strictly exploitative: there was no improvement of natural pastures, and
labor (a signii cant share of it provided by children) was coni ned to herding (with
a single person often responsible for hundreds of cattle and even larger herds of
sheep or goats), guarding (sometime including the construction of temporary enclo-
sures), and watering the animals. As a result, the ecological efi ciency of pastoral
subsistence—the quotient of the food energy of animal tissues consumed by humans
and the forage energy intake of animals—was mostly less than 1% in seasonally
