Introduction to Ecological Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 618

Institute 2002). Breure et al. ( 2005 ) described two mature ecological classification
systems: the Dutch Biological Indicator for Soil Quality (BISQ) and the German
Soil Biological Indicator for Soil Quality (BBSK). These classification systems
enable the monitoring of ecological soil quality.

13.9.4.1 Biological Indicator for Soil Quality (BISQ)

The Dutch Biological Indicator for Soil Quality (BISQ) includes information on
the presence, the amounts and activities of organisms, the rate of organism-induced
processes, as well as abiotic factors, as indicators for ecological soil quality (Breure
et al. 2004 ). The actual values of these parameters are related to predefined refer-
ence values. The result can be visualized by a so-called 'amoeba' which gives the
distance-to-target scores for all different factors as fan-shaped segments. In Fig. 13.4
an example of such an amoeba is given for ten Ecosystem Services for four farms
in the Hoeksche Waard, the Netherlands, and compared with the national reference
for arable farmland on clay (100% circle) (Rutgers et al. 2008 ).
In general, three different targets can be used, namely, minimal soil quality,
acceptable soil quality and optimal soil quality. To determine an acceptable soil
quality, a reference ecological soil quality, adapted from nature reserves or biolog-
ical farms with comparable soil types and abiotic characteristics, must be defined.
Another option is to make a theoretical reference, based on knowledge of the consti-
tution of a stable or desired system. In Section 13.5.1 , it was stressed that a pristine
ecosystem is not necessarily an optimal ecosystem.
The BISQ is generally believed to be a comprehensive tool for monitoring soil
quality, covering nearly the entire soil food web. The big drawback, however, is that
it requires intensive sampling and analyses of a whole range of biological and abiotic
parameters. For this reason, it has been suggested that a smaller set of parameters
should be developed that need to be measured in order to achieve a better quality
versus cost ratio.

disease and pest control 93%

resistance
and resilience 89%

soil structure 72%

adaptation 73%

nutrient retention 69%

Fig. 13.4 A so-called
'amoeba', showing the
distance-to-target scores for
relevant Ecosystem Services
as fan-shaped segments,
visualising ecological soil
quality (source: Rutgers et al.
( 2008 ); reproduced with
permission)

biodiversity 84%

turnover OM 76%

natural
attenuation 109%

climate
functions 116%

water retention 79%