Leon Green-Tkacenko and co-authors share insight into their recent study that explores how existing vulnerability indices for seabirds can be applied to migrating songbirds, and potentially other migrating birds, in evaluating vulnerability to offshore wind turbine morality.
What is the problem?
Climate change is the most pressing threat to biodiversity in the 21st century and
addressing this threat will require substantial changes to how we generate electricity. Currently, in the United States around 60% of electricity is generated by fossil fuels. Globally, as we transition away from fossil fuels, we must increase renewable sources of electricity production, but these renewable sources are not entirely without ecological impacts.
Offshore wind energy is one of the most promising forms of renewable energy currently under development in North America, with over 9,000 sq km of offshore wind farm areas planned. Offshore wind has proven to be an effective and green means of energy production in Europe, where its ecological impacts have been relatively well studied. One potential effect of offshore wind turbines is their potential to act as a barrier for some species (above or below water) in an area that, for all of history, has been free of such obstacles.
Despite extensive research for some groups like cetaceans and seabirds, one group of species for which little research has been completed are the migratory songbirds of eastern North America. Some of these species migrate at night over the open ocean during their fall migration, potentially putting them at risk of collision with offshore wind facilities.
What did we do?
My co-authors and I had originally hoped to model the risks facing migratory songbirds from offshore wind facilities, but we quickly realized that so little information is available for these species offshore that we could not make much headway. The lack of basic information on songbird migration over open ocean is due, in part, to the substantial difficulty in conducting research offshore on small flying animals, which largely migrate at night.
Instead, we looked to the early research on the impacts of offshore wind facilities on European seabirds as a potential model. We found that European researchers began by documenting different factors about each species’ biology and behavior to help them gauge the relative risk that each species might face from the siting and operation of offshore wind facilities. We sought to do the same for the migratory songbirds in eastern North America.
We created an ecological vulnerability index for 101 species of migratory songbirds that could reasonably be expected to traverse the open ocean in their autumn migration across the northwest Atlantic ocean. An ecological vulnerability index is a method of estimating relative risk in a transparent and repeatable way. We combined six different factors that could influence in-flight collision risk from offshore wind facilities.
Two of the factors represented how ‘sensitive’ a species is to offshore wind; that is, what is their relative ability to avoid collision with them. Two factors represented relative ‘exposure’ to offshore wind; in other words, to what extent are they physically present in the area where offshore wind is planned and when during the day are they there. Finally, we looked at two factors that impact how resilient a species might be to additional mortality, their population status and trend.
What did we find?
We found that many migratory song birds in the Northwest Atlantic are not particularly vulnerable to offshore wind facilities, but that several species appear to be at potentially outsized risk. In particular, we found that Blackpoll Warbler, Common Yellowthroat, and Bicknell’s Thrush topped our list of most exposed species. Blackpoll Warbler was the most vulnerable species identified in our study. This makes sense as the entire global population of Blackpoll Warbler is thought to migrate over the Northwest Atlantic every fall.
We also explored how conservation efforts on land might impact how vulnerable a
migratory songbird species may be to offshore wind facility collisions. We found that, for many species, moving their population trend in a more positive direction via land based conservation efforts has the potential to dramatically reduce their overall vulnerability to additional mortality from offshore wind.
We hope that our research can serve as a jumping off point for future research towards ensuring an environmentally responsible green energy transition. Researching migrating songbirds offshore is difficult. Using ecological vulnerability indices to identify the species that migrate over open ocean in the Northwest Atlantic that are most at risk of mortality from offshore wind is a first step. Field biologists and regulators can then take this information and focus their efforts on species most in need to ensure that any substantial risks are reduced, if not eliminated, via mitigation actions.
Read the full article “An ecological vulnerability index to assess impacts of offshore wind facilities on migratory songbirds” in Journal of Applied Ecology.
