Environmental Engineering Reference
In-Depth Information
conservation ' and ' ecological restoration ' , and points
of view may even change over time. In large parts of
northern and central Europe and indeed the entire
northern hemisphere, the forests and woodlands
that developed after the last Ice Age ended, approxi-
mately 11 000 years ago, have repeatedly been
exploited or even clear-cut for timber, and the lands
they formerly occupied cleared and burnt to make way
for agricultural production systems. Though this dis-
turbance, or transformation, from forest or woodland
to farmland and pasture sometimes resulted in heavy
soil erosion, it was generally considered as a gain for
the farmers, and for the entire society. From the Middle
Ages up to the beginning of the twentieth century, the
prevailing land use in Europe was low-intensity
farming, resulting in agro-ecosystems such as species-
rich meadows and open heathlands , currently known
as seminatural ecosystems. In Figure 1.3, we illustrate
this notion schematically, in the broader context of the
range of anthropogenic disturbances to ecosystems
and the alternative states or conditions presented
already in Figure 1.2 .
After the introduction of artifi cial fertilizers in the
early twentieth century, the application of which
enables intensive production of food, these less inten-
sively used farmlands were no longer considered as a
gain; instead they were called 'non-use lands' or even
' wastelands ' that should, logically, be ' reclaimed ' for
production. Large-scale fertilizer application resulted
in a new change of the ecosystem state, from low-
intensity farmlands to increasingly high-input, high-
production systems. Again, this change was appreciated
by most farmers, but not by all members of society,
especially those concerned with sustainability . The
high level of nutrient supply to the soil resulted in a
steep decline in biodiversity , not only in the cultivated
areas, but also in adjacent landscapes. Nature conser-
vationists, who had taken initiatives to establish formal
nongovernmental institutions to counteract the
ongoing process of what they considered as degrada-
tion of the environment, were gradually supported by
scientists from universities and research institutions
who conducted detailed studies and provided quantita-
tive data on the impacts. Increasingly, points of view
Low
1
2
Human
impact
3
4
High
Over-exploitation
Near natural
Seminatural
Production
System type
Figure 1.3 Schematic representation of common transformations of ecosystems. Arrows from left to right indicate
anthropogenic disturbances; arrows from right to left indicate options for ecological restoration or rehabilitation, or,
alternatively, reclamation to some type of sustainable system. Note that the route to recovery or restoration of an ecosystem
after prolonged disturbance and profound transformation often takes much longer than, and differs from, the initial route of
degradation. This discrepancy is known as hysteresis. It is important that restorationists and restoration scientists not forget or
underestimate this factor of unpredictability, which generally increases in correlation to the degree of human impact.
 
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