Introduction to Ecological Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 591

a contribution to the fixation of greenhouse gasses. A nice example is the fixation of
CO 2 in soil organic matter, which is taken into account in the Kyoto climate treaty.
A nice example of the application of soil organisms to avoid the methane produced
in waste dump sites entering the atmosphere is by covering the dump with a layer
of soil, so that the methane is oxidised into CO 2 . Methane is a much more potent
greenhouse gas than carbon dioxide, and reduction of its emission damps down
climate change.
An extremely interesting development with regard to clean energy sources is
related to the use of insoluble electron acceptors by anaerobic soil organisms. This is
a natural process occurring in anaerobic soils in the degradation process of organic
matter in the absence of nitrate or sulphate as electron acceptors. This process is
being investigated now to produce so-called Bio-electrochemical systems ( BESs )
that use the electrical energy supplied by bacteria for energy production. In so
doing, these bacteria, also so-called Microbial Fuel Cells ( MFCs ), produce electric-
ity and can be considered as small batteries. These bacteria live on organic matter
secreted from rice plants, and leave water and carbon dioxide behind. So far, plain
electrical power production combined with wastewater treatment by Microbial Fuel
Cells has been the primary application of BESs (Clauwaert et al. 2008 ; Stams et al.
2006 ). A wide variety of bacteria can participate in this electron transfer, and this
phenomenon is far more widespread than previously thought (Rabaey et al. 2007 ).
13.4.4 Above-Ground Biology
Most of the Ecosystem Services described above (Sections 13.4.3.2 , 13.4.3.3 ,
13.4.3.4 , 13.4.3.5 , and 13.4.3.6 ) take place beneath the soil's surface, but have
a direct impact on developments above ground. This is most directly reflected
by above-ground plant growth, either related to man-grown crops, as is the case
in agriculture, horticulture or gardening, or related to herbs, bushes and trees in
nature reserves, shoulders, and in fact on practically every bare patch of the planet.
Indirectly, the presence of vegetation strongly impacts the presence of all other
forms of wildlife, ranging from small insects on up to large animals such as deer
or bears. The presence of trees and plants is an extremely important element in the
daily life of almost every citizen, both in rural and urban areas. And for these trees
and plants, a healthy soil ecosystem is an elemental boundary condition.
13.4.5 Agriculture
The relationship between agriculture and the soil ecosystem is a typical example of a
love-hate relationship. Traditionally, farmers are very much aware of the crucial role
that the subsurface biology plays in successful agricultural production. Although
they might not fully comprehend the details of the magnificent biological and abiotic
processes that are ongoing in soils, they generally are convinced of the necessity to
care for the soil ecosystem. In fact, practically every function the soil ecosystem