Abstract
- Offshore windfarms are likely to become one of Europe’s most extensive technical interventions in marine habitats. European inshore coastal and offshore marine waters support globally significant numbers of seabirds and the UK Government has legal obligations to monitor the effects coastal developments will have on populations of these species.
- Although conventional impact assessments allow estimates of the number of birds that might collide with or be displaced by windfarms, such methods do not allow the overall effect on bird populations to be established. This report determines whether sufficient demographic information is available to carry out population viability analysis: one method of determining the impacts of offshore windfarms on bird populations.
- We consider the data availability for the following species, which we consider the most likely to be affected by offshore windfarms: red-throated diver (Gavia stellata), black-throated diver (Gavia arctica), great crested grebe (Podiceps cristatus), fulmar (Fulmarus glacialis), gannet (Morus bassanus), cormorant (Phalacrocorax carbo), shag (Phalacrocorax aristotelis), eider (Somateria mollissima), common scoter (Melanitta nigra), velvet scoter (Melanitta fusca), arctic skua (Stercorarius parasiticus), great skua (Catharacta skua), little gull (Larus minutus), black-headed, gull (Larus ridibundus), common gull (Larus canus), lesser black-backed gull (Larus fuscus), herring gull (Larus argentatus), great black-backed gull (Larus marinus), kittiwake (Rissa tridactyla), sandwich tern (Sterna sandvicensis), arctic tern (Sterna paradisaea), little tern (Sternula albifrons), guillemot (Uria aalge), razorbill (Alca torda) and puffin (Fratercula arctica).
- For most species likely to be affected by offshore windfarms, sufficient demographic data exist to carry out population viability analyses. There is good information on adult survival for all species with the exception of little tern and little gull. Similarly, for all species except little gull, there is good information on productivity. Reasonable data on age-dependent survival and productivity and on the proportion of non-breeders and inter-colony movements are available for about half of the species assessed.
- However, there are some limitations with regards to what population viability analysis can achieve. Mortality resulting from windfarms may reduce competition for resources, thus reducing the rate of natural mortality. The extent of the latter cannot be determined solely through conventional population viability analysis, but also requires detailed understanding of the extent to which demographic parameters are density-dependent. Reasonable data on density-dependence are only available for three species: cormorant, shag and kittiwake. A summary of data availability is given in Table 2.
- Nevertheless, population viability analysis provides a robust framework for taking a scenarios-based approach in which likely impacts are determined using upper- and lower-bound estimates of unknowns. As such, best-case and worse-case scenarios could be determined.