IMPACTS OF OFFSHORE WINDFARMS ON POPULATIONS AND DEMOGRAPHY OF GANNETS: REDUCING UNCERTAINTY IN RISK ASSESSMENTS

There is an urgent need to understand how offshore wind farms could affect marine biodiversity. Here, the student will combine advanced demographic analysis and state-of-the-art wildlife tracking to provide critical insight into how mortality through collisions with offshore turbines could affect long-term population viability of a high-profile marine predator of high conservation status in the UK, developing a much-needed framework to assist with consenting decisions for marine renewable energy developments.

A large increase in offshore wind turbine capacity is anticipated in the next decade, raising concerns about possible adverse impacts on birds as a result of mortality caused by collisions with turbine blades. Gannets have been identified as a species of particular concern but there is great uncertainty over the likely consequences of additional mortality for gannet population sizes. The student will use a unique combination of demographic modelling, field tracking data and digital aerial survey data to address four aims:

1. Modelling gannet population dynamics. Using several decades of demographic data for gannet colonies around the UK and NW Europe, the student will: (A) Develop stage-structured matrix models incorporating density-dependent survival, breeding success and natal vs non-natal recruitment for individual gannet colonies and for the UK population as a whole; (B) Test model goodness of fit by retrospectively projecting population growth over the past three decades, for which very reliable population size data are available, and; (C) Refine models using a Bayesian framework to test effects of spatial and temporal variation in vital rates on population dynamics.

2. Assessing potential effects of wind farms on stage-specific mortality. The student will: (A) Use extensive existing data on foraging tracks of adults at different colonies around the UK and NW Europe, combined with novel data on tracks of immature birds obtained using GPS-GSM loggers, to quantify and compare densities of adults and immatures at sea; (B) analyse digital aerial survey data from existing windfarms to determine turbine avoidance rates by adults and immature birds, and; (c) use these data to quantify the extent to which mortality imposed on adults and younger birds could plausibly differ.

3. Predicting impacts of heightened mortality on population dynamics and viability. Using a life-table response experiment (LTRE) framework, the student will examine the extent to which plausible increases in stage-specific mortalities would change population projections for individual gannet colonies over a period of 30 years (the likely operating periods of offshore wind farms). S/he will then use a meta-population framework to examine how the imposition of source-sink dynamics through heightened mortality at large colonies (which are very attractive to prospecting pre-breeders) would simultaneously affect projected population changes at colonies across NW Europe.

4. Informing advice on policy. Working closely with project partners, s/he will consider the implications of the results from 1-3 in terms of: (i) advising on how different levels of imposed stage-specific mortality would affect gannet population dynamics and colony sizes, and; (ii) developing broadly applicable tools that could be parameterized for other species and in other contexts to reduce the uncertainty associated with planning consent decisions.