Report from the Sub-comittee on the environment and health

Behandlingshyppighed
Sandsynligheden for effekter på alger i
vandhuller i 4 scenarier
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0,26 10
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0,59
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20
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1,17
45
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2,34
85
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0 20 40 60 80 100
Sandsynlighed i %
Figure 10.10
The model-based probability of effects on algae in typical Danish ponds
in four scenarios with different crop distribution and treatment frequency
index (<strong>from</strong> Møhlenberg, Gustavson 1999).
(Figure texts:
Sandsynligheden for effekter på alger i vandhuller i 4 scenarier =
Probability of effects on algae in ponds in 4 scenarios
Behandlingshyppighed = Treatment frequency index
Sandsynlighed i % = Probability in %)
Correspondingly for crustaceans, <strong>the</strong> probability of effects with more
than 10% inhibition is about 55% in <strong>the</strong> 2.34 scenario, about 25% in <strong>the</strong>
1.17 scenario, about 15% in <strong>the</strong> 0.59 scenario and about 10% in <strong>the</strong> 0.26
scenario, as shown in figure 10.11.
Halving <strong>the</strong> treatment frequency index greatly reduces <strong>the</strong> probability of
effects, since several years pass between events where considerable
effects can be expected. As an example, in potatoes, <strong>the</strong> frequency of
100% inhibition of crustaceans decreases <strong>from</strong> 70% in <strong>the</strong> 2.34 scenario
to about 35% in <strong>the</strong> 1.17 scenario. Correspondingly, <strong>the</strong> frequency of
events with sublethal inhibition (up to 10% effect) is halved <strong>from</strong> 100%
in <strong>the</strong> 2.34 scenario to 50% in <strong>the</strong> 1.17 scenario (Møhlenberg, Gustavson
1999).
It can thus be concluded that <strong>the</strong> model calculations for ponds show a
probability of effects on both flora and fauna as a consequence of run-off
in all four scenarios. The probability of effect falls with <strong>the</strong> quantity of
pesticides used in <strong>the</strong> scenarios.
207