Name: Mark Trinder
The report describes an approach for assessing the collision risk of diving birds with marine renewable energy devices, known as the exposure time population model (ETPM). The approach explores the collision rate required to achieve a critical level of additional mortality by estimating (i) thresholds of additional mortality for the population at risk of collision and (ii) the potential time that each individual within the population is at risk of collision. A judgement is then made as to whether the maximum acceptable collision rate is likely to occur or not.
The ETPM approach provides a broad based assessment of the potential impact of collisions with tidal turbines on populations of diving birds. Given the limited knowledge base and poor understanding of the underwater movements of diving birds and their behavioural responses to underwater devices, this approach is considered an appropriate and useful method for assessing collision risk of diving birds.
The project is complete and a report has been published.
- The report sets out the rationale for the ETPM approach;
- Parameters from which exposure time is estimated are described, along with the means by which these parameters can be derived from a combination of data extracted from the available literature and obtained from site-based measurements;
- The modelling approach is illustrated using two example species (European shag Phalacrocorax aristotelis and common guillemot Uria aalge) at an unspecified proposed tidal development in the Pentland Firth, northeast Scotland. These examples indicate that the collision rate required to exceed the ‘acceptable’ threshold of additional mortality is considerably lower (and hence the collision risk higher) for shag than for guillemot at this site, in keeping with the higher on-site densities and smaller source population of the former species.
- Exposure time estimates are shown to be relatively sensitive to variation in several of the input measurements, some of which have considerable uncertainty associated with them. This has consequences for the derivation of the ‘required’ collision rate, although in some situations at least there is likely to be scope to reduce uncertainty in some measurements through targeted on-site data collection.
- The ETPM approach provides a broad based assessment of the potential impact of collisions with tidal turbines on populations of diving birds. This level of assessment is considered to be appropriate given the limited knowledge base and poor understanding of the underwater movements of diving birds and their behavioural responses to underwater devices, including their ability to evade the rotating turbines.