128
Second, depending on the type of oil being spilled, weather conditions and sea
currents, the ecological and social impacts can vary dramatically. For example, icy
conditions make cleanup activities especially cumbersome. Third, the long-term
effects of oil spills on complex ecosystems are not well known (National Research
Council 2003 ). Whether or not oil sinks to the bottom and continues to affect
specifi c communities and ecosystems for a long time depends on the type of oil and
local conditions. Possibly, oil spills can increase physiological stress, reduce food
supply and cause reproduction disturbances.
Taken together, these uncertainties make it impossible to in detail predict impacts
of large-scale oil spills. Although political agreements may be reached on the
importance of reducing risks, questions related to which particular measures are
most cost-effi cient cannot be defi nitely given as long as it is not possible to assess
risks in detail.
The ecological impact of the many almost continuous small-scale intentional
spills that take place in the Baltic Sea is quite different from the large-scale ones and
more diffi cult to delineate. Although it could be expected that operators choose to
clean tanks in ways that minimise risks of being spotted, existing data on where oil
spills have been detected show a rather uniform distribution during the last 10 years
along the major sea lanes (possibly with some clusters at the entrance of the Gulf of
Finland and in the Great Belts) (HELCOM 2014 ). There are four kinds of major
environmental concerns linked to intentional spills. First, many small spills occur
close to ports as a result of loading and unloading and may cause disturbances to
local ecosystems. Most of these spills are not intentional, but rather the result of
improper procedures or human error. Despite this, they are typically classifi ed as
“intentional” in order to distinguish them from large-scale accidental spills.
1 Second,
even though these smaller spills occur along the major shipping lanes in general,
there seem to be some clusters where spills are more common. Environmental
hazards typically increase the denser these clusters are. Third, where the spills take
place is of importance. Comparably large spills in favourable weather conditions
and far away from ecologically sensitive areas may not cause much observable
harm, whereas small spills could cause substantial damage if they occur close to
sensitive areas, in unfavourable weather conditions and in critical seasons when
different marine-living species might be reproducing. Finally, the Baltic Sea is an
ecologically sensitive sea because of its brackish water, slow water exchange with
the North Sea and the halocline (salinity gradient) that reduces vertical mixing of
water and thereby leads to reduced oxygen concentrations in deep basins.
1 It could be argued, for example, that operational spills might be a better label than intentional
spills, as the former places the focus on oil spills that result from everyday procedures rather than
from accidents. However, since intentional spills is the term used in most of the literature, we have
chosen to stick to this term when referring to small-scale spills caused by negligence, improper
procedures or something similar.
B. Hassler
Second, depending on the type of oil being spilled, weather conditions and sea
currents, the ecological and social impacts can vary dramatically. For example, icy
conditions make cleanup activities especially cumbersome. Third, the long-term
effects of oil spills on complex ecosystems are not well known (National Research
Council 2003 ). Whether or not oil sinks to the bottom and continues to affect
specifi c communities and ecosystems for a long time depends on the type of oil and
local conditions. Possibly, oil spills can increase physiological stress, reduce food
supply and cause reproduction disturbances.
Taken together, these uncertainties make it impossible to in detail predict impacts
of large-scale oil spills. Although political agreements may be reached on the
importance of reducing risks, questions related to which particular measures are
most cost-effi cient cannot be defi nitely given as long as it is not possible to assess
risks in detail.
The ecological impact of the many almost continuous small-scale intentional
spills that take place in the Baltic Sea is quite different from the large-scale ones and
more diffi cult to delineate. Although it could be expected that operators choose to
clean tanks in ways that minimise risks of being spotted, existing data on where oil
spills have been detected show a rather uniform distribution during the last 10 years
along the major sea lanes (possibly with some clusters at the entrance of the Gulf of
Finland and in the Great Belts) (HELCOM 2014 ). There are four kinds of major
environmental concerns linked to intentional spills. First, many small spills occur
close to ports as a result of loading and unloading and may cause disturbances to
local ecosystems. Most of these spills are not intentional, but rather the result of
improper procedures or human error. Despite this, they are typically classifi ed as
“intentional” in order to distinguish them from large-scale accidental spills.
1 Second,
even though these smaller spills occur along the major shipping lanes in general,
there seem to be some clusters where spills are more common. Environmental
hazards typically increase the denser these clusters are. Third, where the spills take
place is of importance. Comparably large spills in favourable weather conditions
and far away from ecologically sensitive areas may not cause much observable
harm, whereas small spills could cause substantial damage if they occur close to
sensitive areas, in unfavourable weather conditions and in critical seasons when
different marine-living species might be reproducing. Finally, the Baltic Sea is an
ecologically sensitive sea because of its brackish water, slow water exchange with
the North Sea and the halocline (salinity gradient) that reduces vertical mixing of
water and thereby leads to reduced oxygen concentrations in deep basins.
1 It could be argued, for example, that operational spills might be a better label than intentional
spills, as the former places the focus on oil spills that result from everyday procedures rather than
from accidents. However, since intentional spills is the term used in most of the literature, we have
chosen to stick to this term when referring to small-scale spills caused by negligence, improper
procedures or something similar.
B. Hassler