Offshore wind farms could change ocean ecosystems in unexpected ways

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By 2030, it’s expected that offshore wind turbines will produce some four percent of Europe’s energy. That’s forty times more energy than they do now. So what will it mean to have forests of 600-foot-tall turbines off the coast of western Europe? What sort of life will they support, and what will that mean for ecosystems in the North Atlantic?

Quite a bit, and it’s complicated, suggest scientists from Germany’s Helmholtz-Zentrum Geestacht Centre for Materials and Coastal Research. Led by ecologists Kaela Slavik and Carsten Lemmen, they extrapolate data on fauna presently found on offshore wind turbines and it to the projected range of wind farms. The long-term effects — a dramatically expanded range for one keystone species, a decline in total ecological productivity — defy a simple good-or-bad analysis.

Primary production, or the sheer amount of biomass produced in an ecosystem, could decline by up to several percent. Driving that decline is the expected proliferation of filter-feeding blue mussels that grow on turbine infrastructure and remove plankton from the water. Less plankton will be available for other animals, especially small or juvenile fish who now feed on blooms. The models suggest it won’t be a huge impact, but neither will it be negligible.

At the same time, blue mussels are an ecosystem engineer. Their aggregations create habitat for other creatures and their bodies are sustenance for large fish, crustaceans and marine mammals. Wind farms project to increase their regional range by 20 percent, and local biodiversity could increase as a consequence of their presence — though some of that diversity will likely be non-native species rushing to fill the newly-constructed turbines.

Those non-natives could produce more diverse, more resilient ecosystems — or not. And there will, of course, be negative effects from construction and noise and bird strikes in the turbines. Yet wind farms are usually declared off-limits to fishing, especially destructive bottom trawling, creating protected areas in which life can thrive.

The study was released on the pre-publication site arXiv and hasn’t yet been full through peer review; the authors note that “there are still large uncertainties related to simulating complex ecosystem interactions.” So take the precise details with that caveat. The big picture, though, seems clear: the effects of offshore wind turbines are going to be complicated.

Source: Slavik et al. “The large scale impact of offshore windfarm structures on pelagic primary production in the southern North Sea.” arXiv, 2017.

Image: The Danish Wind Industry Association / Flickr

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