Risk Assessment in Ballast Water Management - Global Maritime Transport and Ballast Water Management: Issues and Solutions - page 151

to ensure reliable data quality. This is to avoid that exemptions are wrongly ongoing
in cases of new species arrivals. We recommend that such monitoring (surveys)
needs to be established regularly (e.g., every 6 or 12 months) to deliver reliable and
current information.
Applying the precautionary principle, in cases where reliable data are lacking, no
RA-based exemption can be granted. This is especially important where a RA relates
to environmental and human health protection (EU Commission 2000 ; IMO 2007 ).
Risk Assessment Methods Applied
Environmental Matching Method
The environmental matching RA method uses environmental parameters as surro-
gates for species. Of the two most frequently used RA parameters, water tempera-
ture and salinity, the salinity variability is the only parameter common to all past
RAs. Furthermore, the more variables a RA includes, the lesser transparent
becomes the decision process. We believe that water salinity is the most “straight
forward” concept, hence the RA presented here uses salinity as the only meaning-
ful environmental parameter. Water temperature was also considered as a RA
quantifying factor in the environmental match approach. However, we believe this
is of lesser reliability to identify low risk scenarios because we assume that organ-
isms are more fl exible regarding temperature tolerances compared to salinity in
temperate and polar regions. One reason for this assumption is the greater tempera-
ture difference compared to salinity difference over the annual seasons which the
species need to tolerate. In the tropics this may be different as the temperature may
be more similar throughout the year and here the rainy seasons may result in a
stronger organism tolerance towards salinity. However, also the use of salinity
shows its weakness. In cases when two ports may have totally different salinity
ranges the RA result will be low risk. However, species salinity tolerance may
cover both environments so that a high risk should have been the result (Hewitt and
Hayes 2002 ; Hayes and Sliwa 2003 ). As a compromise, this RA uses salinity as the
only environmental parameter. The difference between the ballast water donor and
recipient ports as freshwater and marine ports respectively is the suggested accept-
able salinity difference offering acceptable precaution levels to trigger a low risk
result because the number of species being able to tolerate such a large salinity
difference is comparably low (but not zero!).
In a two-step approach we considered that the minimum salinity difference to
assume a low risk for a successful species transfer. A low risk was assumed when
ballast water is moved between freshwater (<0.5 psu) and fully marine conditions
(>30 psu). However, such conditions are rarely applicable in coastal shipping, but
may occur in areas with larger estuaries, run-off of major rivers, when a port is situ-
ated on a river more inland etc. To cope with that situation other possibilities were
considered. What could be acceptable, but at the price of a slightly higher risk, is