Introduction to Ecological Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 592

performs, described in Sections 13.4.3.2 , 13.4.3.3 , 13.4.3.4 , 13.4.3.5 , and 13.4.3.6 ,
supports agriculture. From this perspective, the soil ecosystem could be considered
as livestock.
However, since the 1950s, industrial agriculture, rooted in the massive use of
technology and the application of chemical products, has spread worldwide. In
this technological agriculture farmers did not dare to trust natural processes to
enhance production, and therefore applied chemical and mechanical technology.
Nutrients were applied, not by degradation of the organic residues of plants remain-
ing from the previous growth season, but by the addition of fertilizer. Pest control
was not carried out through a proper design of the farm, providing a place for pest-
reducing organisms, but by the application of pesticides. Tension arose between
fast-production imperatives and more sustainable ways of farming. Soil structure
was no longer supplied by the activity of earthworms and other soil organisms, but
was obtained by tillage, resulting directly in tilling the worms and indirectly by
destroying their tunnels, drying out the soil, burying plant residues they feed on and
exposing the soil to freezing. Tillage destroys the total natural habitat of soil organ-
isms, leading to huge losses of organic matter, due to exposure of organic material
to the surface and thereby to oxygen. In peaty soil especially, this can be seen very
clearly.
Excessive nutrient loading and heavy machinery are also severe threats to the soil
ecosystem. But, over the last decade, as more and more humans have grasped the
impact of industrial agriculture and started questioning its long-term implications,
interest in sustainable agricultural management systems has made a remarkable
come-back. This has resulted in hundreds of topics and publications on this topic, a
rapidly developing market for organic products and many farmers shifting to more
sustainable ways of growing food. In this sustainable agriculture, the application
and use of ecosystem processes is very important and soil organisms have once
more become the appreciated co-workers of farmers.
13.5 Ecological Risk Assessment
13.5.1 Principles
As outlined in Section 1.5.2 , from a more general Risk Assessment perspec-
tive, risks have to do with chance and effect . Before describing Ecological Risk
Assessment, it is useful to define the protection target, that is, the object which
might be affected, in more detail. It is at this point that we reach the very core of
Ecological Risk Assessment, namely, the definition of Ecological Health.
There is no universal concept of Ecosystem Health (De Leo and Levin 1997 ).
Although there is a premise that natural systems are healthier than human-altered
ecosystems (Lackey 2001 ), most ecological debates going on today focus on
Ecosystem Health rather than on Ecosystem Integrity (Westra 1998 ). This is a sound
approach since the unimpaired condition in which ecosystems do not show any