Geography Reference
In-Depth Information
Terracing can also take advantage of and improve microclimates. Slopes facing the
sun are preferred, as the terraced levels collect radiation at a higher angle and thus
have warmer soil. The ability of water to absorb and hold solar energy during the day al-
lows irrigated fields to reach higher elevations than dry fields. Conversely, many of the
low-angle terraces of northern Pakistan also have fruit and nut trees to maximize pro-
ductivity, although the trees are not allowed to shade a neighbor's terrace. The soil on
most terraces is excellent, having been tilled and fertilized with animal and human ma-
nure for centuries. The more inclined terraces are tilled by hand, while the wider (and
usually lower) ones support the traditional animal-drawn plow. Mechanization of any
sort is rare. Thus, terracing greatly improves productivity by transforming steep slopes
into segmented level areas that can be irrigated, fertilized, cultivated, and maintained
on a sustained basis. This is land that otherwise would be under less efficient shifting
cultivation or unfilled altogether. Increasing productivity is of paramount importance in
places like China, with five times the population of the United States but with less than
half the arable land. In recent years, upland farmers in Yunnan have increased yields
by planting improved rice varieties on newly constructed terraces (Wang et al. 2010).
Compensating for a lack of level terrain is important in developing societies where pop-
ulation growth rates are very high.
Terracing is not risk-free, because removing tree cover and regrading slopes can
induce landslides. This is especially true in Rwanda's mountainous Ruhengeri Prefec-
ture, with its heavy rains, earth tremors, and poorly constructed terraces (Byers 1992).
Farmers pile stones and logs along field contours, dig furrows, build fences, and plant
trees to minimize erosion and efficiently decant water along slopes. They increase soil
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