Geoscience Reference
In-Depth Information
200 tons/Km
2
of new soils are currently formed annually by
weathering processes.
23
Erosion processes can often reach dangerous velocity and extent due to human
intervention. Enhanced erosion is a worldwide problem, but particularly pronounced
in tropical and subtropical climates. Between 1958 and 2001, a terrace in the central
loess plateau of China lost 3,400 m
3
km
−
2
a
−
1
of soil. A
cultivation. About 100
-
uvial catchment on clayey
substratum in the Transkei region of the Eastern Cape Province in South Africa
displayed erosion of 5,400 T km
−
2
a
−
1
between 1949 and 1975. In the loess region of
the Palouse, Washington and Idaho, USA, about 7,600 T km
−
2
a
−
1
were eroded
between 1980 and 1998 and on deeply weathered crystalline rocks in Brazil
17,000 m
3
or 23,000 T km
−
2
a
−
1
were displaced between 1850 and 1979.
24
These
measured Brazilian soil destruction rates are more than 100 times higher than the
average rate of regeneration of soil material by weathering
25
. Erosion processes like
this are potentially able to remove the entire soil cover in a few centuries and would
then prevent agricultural use on the long term. But the upscaling of such results is not
easy. Continent-wide estimations seem to be rather doubtful as they are not based on
representative data, much remains incompletely understood.
26
Humans have been aware of soil movement for a long time. In some places (such
as the Andes and central Mexico), soil erosion was stimulated by humans so that
soil could be collected and concentrated to create agricultural surfaces. In other
locations (e.g. Central and West Africa, northern Mexico), soil management sys-
tems were designed to minimize or prevent soil erosion associated with tillage and
vegetation, or to contain soil movement within a
eld by using vegetative
boundaries.
27
Where large scale crop production developed to supply distant
markets, soil erosion was often ignored, went unchecked by human intervention,
and led to large scale soil loss.
28
,
29
3.3 Human Interaction with Soils
3.3.1 Overview
Human interaction with soils predates agriculture. Non-agricultural peoples used
speci
c soils for medicinal purposes and to make pigments, while clay materials
were formed into containers. Red ochre served in burial rituals since Paleolithic
23
Arnold et al. (
1990
).
24
All data from Bork (
2006
).
25
Arnold et al. (
1990
).
26
Pimentel et al. (
1995
), Boardman (
2006
), Cogo and Levien (
2006
) and Flanagan (
2006
).
27
Reij et al. (
1996
).
28
Showers (
2006
).
29
The preceding chapter
3.2.2.1
Erosion is based on Winiwarter et al. (
2012
).
