Page 330 - Fundamentals of Geomorphology

AEOLIAN LANDSCAPES 313

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of 625 g/m /yr. A lower rate of deposition will lead to containing seeds, damage crops by sandblasting them,
dilution by weathering, by mixing by burrowing ani- and block ditches and roads. Blowing is recorded as long
mals, by mixing with other sediments, and by colluvial ago as the thirteenth century, but the problem worsened
reworking. During the late Pleistocene in North America during the 1960s, probably owing to a change in agri-
and Western Europe, loess accumulated at more than cultural practices. Inorganic fertilizers replaced farmyard
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2 mm/yr, equivalent to 2,600 g/m /yr. manure, heavy machinery was brought in to cultivate and
harvestsomecrops,andhedgerowsweregrubbedtomake
fields better-suited to mechanized farming. Intensively
HUMANS AND AEOLIAN LANDSCAPES cultivated areas with light soils in Europe are generally
prone to wind erosion and the subject of the European
Wind erosion may bring about long-term impacts on Union research project onWind Erosion and European
humansandhumanactivities.Itmaydamageagricultural Light Soils (WEELS) (e.g. Riksen and De Graaff 2001).
and recreational lands, and, on occasions, impair human This international project began in 1998 and looked at
health. As Livingstone and Warren (1996, 144) put it: sites in England, Sweden, Germany, and the Netherlands
where serious wind-erosion problems occur.The damage
There has been and continues to be massive investment across recorded depended very much on landscape factors and
the world in the control of aeolian geomorphological processes. land-use. Most on-site damage, mainly in the form of
It has happened in Saharan and Arabian oases for thousands crop losses and the cost of reseeding, occurred in sugar
of years; on the Dutch coast since the fourteenth century; on
the Danish sandlands particularly in the eighteenth and nine- beet, oilseed rape, potato, and maize fields. In the cases
teenth centuries; in the Landes of south-western France from the of sugar beet and oilseed rape, the costs may be as much
nineteenth century; in the United States since the Dust Bowl of as E500 per hectare every five years, although farmers
the 1930s; on the Israeli coast since shortly after the creation are fully aware of the risk of wind erosion and take pre-
of the State in the late 1940s; on the Russian and central Asian ventive measures. In Sweden, measures taken to reduce
steppes since the Stalinist period; since the 1950s in the oil-rich wind erosivity include smaller fields, autumn sowing,
desert countries of the Middle East; since the early 1970s in the
Sahel, North Africa, India and China; and less intensively but rows planted on wind direction, mixed cropping, and
significantly in other places. In most of these situations, applied shelterbelts. And measures taken to reduce soil erodibil-
aeolian geomorphology won huge resources and prestige. ity include minimum tillage, manuring, applying rubber
emulsion, watering the soil, and pressing furrows.
The chief problems are the erosion of agricultural soils,
the raising of dust storms, and the activation of sand
dunes, all of which may result from human disturbance, Modelling wind erosion
overgrazing, drought, deflated areas, and the emissions Researchers have devised empirical models, similar in
of alkali-rich dust (see Livingstone and Warren 1996, form to the Universal Soil Loss Equation (p. 179), to pre-
144–71). dict the potential amount of wind erosion under given
conditions and to serve as guide to the management prac-
tices needed to control the erosion. The Wind Erosion
Cases of wind erosion
Equation (WEQ), originally developed by William S.
The Dust Bowl of the 1930s is the classic example of Chepil, takes the form:
wind erosion (Box 12.2). Even greater soil-erosion events
occurred in the Eurasian steppes in the 1950s and 1960s. E = f (I, C, K , L, V )
On a smaller scale, loss of soil by wind erosion in Britain,
locally called blowing, is a worse problem than erosion by where E is the soil loss by wind, I is the erodibility of
water. The light sandy soils of East Anglia, Lincolnshire, the soil (vulnerability to wind erosion), C is a factor
and east Yorkshire, and the light peats of the Fens are the representing local wind conditions, K is the soil surface
most susceptible. Blows can remove up to 2 cm of topsoil roughness, L is the width of the field in the direction of