62. 63.
The sensitivity level of marine mammals to each type impact is justified within the impact assessment.
The sensitivity of marine mammals to impacts from pile driving noise is currently the impact of most concern across the offshore wind sector. The sensitivity to potential impacts of lethality, physical injury, auditory injury or hearing impairment, as well as behavioural disturbance or auditory masking have been considered for each species, using available evidence including published data sources.
12.4.3.2 Magnitude 64.
The significance of the potential impacts of East Anglia THREE is also based on the intensity or degree of disturbance to the baseline conditions and is categorised into four levels of magnitude: high; medium; low; or negligible, as defined in Table 12.8.
65.
The thresholds defining each level of magnitude of effect for each impact have been determined using expert judgement, current scientific understanding of marine mammal population biology and JNCC et al. (2010a) draft guidance on disturbance to EPS species. The magnitude of each effect is calculated or described in a quantitative or qualitative way within the assessment.
66.
The JNCC et al. (2010a) draft guidance provides some discussion on how many animals may be removed from a population without causing detrimental effects to the population at FCS. As such this guidance has been considered in defining the thresholds for magnitude of effects. All species considered in this assessment (both cetaceans and pinnipeds) are high value so using the JNCC et al. (2010a) draft guidance is deemed appropriate in assigning the thresholds for magnitude of effect presented in Table 12.8.
67.
The number of animals that can be ‘removed’ through injury or disturbance will vary between species, but is largely dependent on the growth rate of the population; populations with low growth rates can sustain the removal of a smaller proportion of the population. For most species of cetacean there is a large amount of uncertainty as to the growth rate of the population, but JNCC et al. (2010a) consider that it is generally accepted that for cetaceans the population growth rates will be lower than 10% per year. The Guidance states that:
“An IWC/ASCOBANS workshop in 2000 recommended that 4% a year should be used as a conservative estimate of the maximum potential growth rate for harbour porpoise. This value is generally accepted as the default for cetaceans and in the absence of better information is considered a reasonable measure that could be used”.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 12 Marine Mammal Ecology Page 32
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