Risk management of chemicals and contaminated land – from planning to verification - Environmental Deterioration and Contamination: Problems and their Management - page 271

4.4 Special risk management measures for ecological areas
The management of natural ecosystems aims to assess and reduce risks to a level
which ensures the healthy ecosystem functions and services required for the recovery,
regeneration and maintenance of a healthy ecosystem.
Minimization of the residual risk ensures long-term functioning of the habitats
to guarantee the ecosystem's sensitive, protected, etc. features. The risk management
of contaminated sites requires a close cooperation between owners, future land users,
responsible authorities, nature conservation bodies and organizations to identify the
management goals. In the Ajka red mud spill in Hungary in 2010, protected wet-
lands (Natura 2000, 1992), fish ponds, hatcheries were impacted and required special
management measures to take special care of certain protected species and establish
hatcheries to substitute lost habitats.
The management of endangered ecosystems uses site-specific ecological data and
information on endangered species, diversity, sensitivity, key species and their habitats,
as well as the magnitude and severity of the risk, its long- or short-term duration and
distribution. Risk-increasing and -reducing natural processes (natural attenuation), the
sensitivity of the ecosystem, its self-recovery potential are important factors which can
significantly influence the scale of risk.
Prevention is the most efficient RMO for the natural environment. If prevention is
not satisfactory for a certain level of ecosystem protection, RR measures are necessary.
Concerning the ecosystems, the habitat's sensitivity and vulnerability are extremely
important factors. The endangered species may be highly sensitive to the contaminant.
This means that the generally used criteria of 95% probability level in maintaining
natural diversity should be increased and more stringent criteria should be applied for
the conservation or rehabilitation measures than normally.
Risk posed to ecosystem habitats such as surface waters and natural land should
be assessed in the vicinity of the ecosystem receptors, i.e., generally at a great distance
from the contaminant source. This may however be accompanied with high uncertainty
in the predicted contaminant concentration. Numerical modeling used to calculate the
risk posed by contaminants on the ecosystem promises little success. Direct assessment
of the contaminant may be misleading, because the response of the ecosystem depends
greatly on other contaminants being present and on environmental conditions. That is
why measuring the effect on the ecosystem itself is more reliable and efficient. Both field
assessments of ecosystem characteristics (density, diversity and other quality indicators)
and direct toxicity testing of field samples are feasible methods to provide information
on the damage to diversity and on aquatic or terrestrial toxicity.
The main task of ecosystem assessment on contaminated land is the identifica-
tion of adverse effects on the ecosystem. In the environment, large variation in the
types and numbers of ecosystem members as well as a broad density and diversity
range of species can be observed. This produces a wide range of acceptable concen-
trations or protective levels for hazardous contaminants, therefore an acceptable level
e.g. for humans, cannot be found. Uncertainty is further increased by susceptibil-
ity and recuperation potential of the ecosystem, bioavailability of the contaminants,
the impact of seasonal changes or the life cycle of the community species. To avoid
uncertainties, protective levels are best determined on a site-specific basis. Short-
term and long-term impacts should be handled in an integrated way. The interaction