Geoscience Reference
In-Depth Information
salinization processes typical for the arid region. Crop yields dropped so much that
the governing centers were obliged to abandon regions where initially fertile soils
gradually became infertile and unproductive. The king and his administration had to
initiate a new administrative center in another area of soils with no or little salinity.
The new region appeared promising to feed the population.
Great damages are caused by soil erosion by the surface water fl ow, especially
when the physical quality of the soil on the surface is strongly reduced. Water fl ow-
ing on the slope of bad-quality soil transports soil particles so intensively that the
most fertile soil layer, the surface horizon, is smashed. With all of the soil particles
being carried away and gullies formed and subsequently washed out, the soil is
fi nally destroyed.
Another example of soil destruction often occurs when the same crop, e.g., wheat
or cotton, is grown year after year on the same fi eld. This practice of monoculture,
already mentioned above relative to plant nutrient availability and soil biodiversity,
also causes deterioration of the strength and stability of the topsoil. Benefi cial small
lumps of soil known as aggregates disintegrate into separated sand, silt, and clay
particles that are detached from the soil surface and carried away by wind forming
dust storms. As the wind subsides and particles settle down, their hot dust scorches
and destroys crop plants in the wind-eroded fi eld as well as those in nearby fi elds.
The destruction of agricultural landscapes by severe dust storms during previous
centuries is well documented by scientifi c evidence. The dust storms remembered
most frequently are those that destroyed large regions in Ukraine of czarist Russia
in the past. Catastrophic droughts accompanying the dust storms were described
also in the classical Russian literature of the nineteenth century. Similar dust storms
and droughts impoverished tens of thousands of American farmers in the 1930s of
the twentieth century. The destructive erosion process, either by wind or by water,
or by combination of both may reach so far that all soil is carried away leaving only
a completely unfertile sublayer and rough rock.
Soil has a miraculous ability to accept many strange materials and to transform
them into an integrated part of its existence. However, if people do not consider the
limits of those capabilities and overload a soil with mineral or organic wastes, the
benefi cial transformation of such wastes into a soil process is no longer a possibility.
With such human negligence, those wastes buried in soil eventually become
unwanted toxic products that gradually overwhelm the soil into a medium that does
not support plant communities.
Modern contemporary society has a new perfect tool for the complete destruc-
tion of soils: constructions. We are not speaking about construction of new houses
and dwellings for still increasing numbers of population. We are speaking about
one- or two-storied shopping centers, warehouses and administration buildings,
roads, and airports. They occupy hundreds of thousands of square kilometers where
the soil was dug out and replaced by concrete, pavement, and asphalt. With the new
surfaces being impermeable and not allowing a drop of rainwater to penetrate into
and down through the remaining subsoil, hydrologic cycles are destroyed. Without
soil, the natural liquidators of wastes, soil microorganisms, do not grow on these
constructed areas and, hence, drastically redistribute the location at which dead
