Introduction to Ecological Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 611

Sobanska ( 2004 ), for example, measured mercury in the hair of wild boars
in Poland. Almli et al. ( 2005 ) measured elevated concentrations of mercury and
lead in crocodiles in the Kafue and Luangwa National Parks in Zambia. And
Duffy et al. ( 2005 ) found higher mercury concentrations in the hair of free-ranging
Alaskan reindeer in the Seward Peninsula, Alaska, US, than in domesticated rein-
deer. Wijnhoven et al. ( 2008 ) measured the concentrations in the liver and kidneys
of voles, mice and mammals in a moderately contaminated flood plain in the
Netherlands. Depending on the effect concentrations used, the extent of exceeding
of these values was measured, mainly for shrew species.
Risk Assessment with regard to wildlife protection is generally based on mea-
surements. Alternatively, exposure models or food-chain models can be used to
calculate potential accumulation in wildlife. Fairbrother ( 2003 ) claimed that meth-
ods for assessing risk to wildlife from exposure to environmental contaminants
remained highly uncertain, as empirical data required for accurate estimates of expo-
sure or determination of toxicity thresholds were lacking. For the purpose of limiting
these uncertainties, the author suggested a tiered methodology based on three mul-
tiple lines of evidence that are gathered by proceeding through a tiered approach,
including:

• the concentration of contaminants in relationship to levels reported to be harmful;

• bioassays or toxicity studies to define dose-response relationships;

• field studies of population or community responses.

13.7.6 Scale and Contaminant Pattern

One important difference with Human Health Risk Assessment and Human Health
Risk Management is the fact that in Ecological Risk Assessment and Risk
Management the degree of ecological damage from soil contaminants is directly
related to the size of the contaminated site. In addition, the Ecological Risk
Assessment must often be approached for a wider area than the contaminated site
alone. The role of area size in Ecological Risk Assessment has a number of reasons
for it. Firstly, unlike Human Health Risk Assessment, ecological damage of an area
is not equal to the sum of the damages at different contaminated sites in that area.
When, for example, small areas are contaminated while the soil and the largest part
of a greater area is clean, Biodiversity and Ecosystem Services are hardly threatened
at all on the scale of the greater area. Alternatively, when the wider surroundings of
a contaminated site are even more contaminated, the ecological value of the region
is not increased that much when this (relatively small) contaminated site is reme-
diated. Big, uncontaminated, or even virgin areas such as the arctic, however, may
never be used as an excuse to trivialise the threat to the soil ecosystem at smaller
contaminated sites within such an area.
Moreover, although most organisms simply reside on the spot were they came
into being, many other organisms are able to migrate to the most optimal locations,
mainly triggered by optimal food supply. An alternative reason for migration is to