Offshore Wind and Marine Life: The 86% We Don't Know

Britain has 15.9 gigawatts of offshore wind capacity powering more than half UK homes, with a pipeline of 95 GW in development. By 2030, offshore wind will be central to generating at least 95% of Great Britain’s electricity from clean sources.

But a January 2024 study analyzing 132 peer-reviewed papers found something uncomfortable: more than 86% of possible offshore wind farm impacts on ecosystem services remain unknown. That’s not a rounding error. That’s deploying infrastructure at scale while admitting we don’t understand most of what it does to the marine environment.

This isn’t an anti-wind argument. Offshore wind is delivering clean energy without the land use conflicts of solar or the waste challenges of nuclear. But when your plan involves covering thousands of square kilometers of seabed with turbines and cables, “we’ll figure it out later” isn’t good enough.

Here’s what we actually know, what we don’t, and why the gaps matter.

The 86% Knowledge Gap: What It Means

The Plymouth Marine Laboratory study, published in January 2024, analyzed 314 pieces of evidence from offshore wind research globally. The researchers examined impacts across 14 ecosystem services—commercial fisheries, carbon storage, water quality, recreational activities, marine biodiversity.

Their finding: 86% of potential impacts are still unknown or insufficiently studied to draw conclusions.

Dr. Stephen Watson, lead researcher, stated: “we desperately need this data to be able to support decision-makers in making decisions during this time of rapid expansion.”

This matters because Britain is not slowing down. The Crown Estate’s Round 4 seabed leasing awarded rights to 8 GW of new offshore wind in 2022. Round 5 could add another 4.5 GW. The pipeline includes floating wind farms off Wales and Scotland. We’re building faster than we’re researching.

What are we missing?

Construction Phase: Noise That Travels Kilometers

The clearest impacts are from construction, particularly pile driving.

When you hammer a 70-meter steel pile into the seabed, the underwater noise travels far. Pile driving creates impulse noise that can kill, injure, or disturb marine mammals without mitigation. Fish exposed to pile driving playbacks become less cohesive, lose directional coordination, and show reduced ability to organize into shoals—behaviors crucial for predation avoidance.

What We Know

Marine mammals avoid construction zones: A December 2024 review by UNEP-WCMC found avoidance is the most common negative impact, primarily during construction.
Mitigation works, partly: Bubble curtains—walls of air bubbles that absorb sound—can reduce noise levels significantly. But they’re limited by currents, which scatter bubbles and reduce effectiveness.
Construction impacts are negative: The Plymouth study found 52% negative construction impacts vs only 8% positive across ecological groups.

What We Don’t Know

Long-term population effects: Does temporary avoidance matter if animals return after construction? Or does it disrupt breeding, feeding, or migration enough to reduce populations?
Species-specific thresholds: At what noise level does a harbour porpoise permanently leave? How does that differ for grey seals, minke whales, bottlenose dolphins?
Cumulative stress: If you’re building 8 GW across dozens of sites over a decade, is the North Sea just perpetually noisy for marine mammals?

Operational Phase: Mixed Evidence

Once turbines spin, the picture gets murkier.

The Plymouth study found operational impacts split almost evenly: 32% negative, 34% positive. Some species benefit from the “artificial reef effect”—turbine foundations and scour protection create habitat for fish and invertebrates. Trawling bans in wind farm zones create de facto marine protected areas.

But other impacts are emerging.

Seabirds: Collision Risk vs Avoidance

Offshore wind turbines kill birds. The question is how many, and whether populations can sustain it.

The RSPB has challenged the proposed Berwick Bank offshore wind farm, arguing it would kill an estimated 329 gannets and 986 kittiwakes annually through collisions, with thousands more impacted by displacement. The organisation states: “Berwick Bank, in its current form, would be more destructive to seabirds than any other proposed offshore wind farm in Scottish waters.”

At nearby St Abb’s Head, two projects combined (Ossian and Berwick Bank) are projected to reduce the kittiwake population by up to 81%.

But other research shows avoidance. A two-year study at Aberdeen Offshore Wind Farm recorded not a single collision between birds and rotor blades. Kittiwakes avoided rotors from 150 meters; gannets from 40 meters. The British Trust for Ornithology recommends avoidance rates of 98.9% for gannets and 99.2% for kittiwakes.

So which is it? Zero collisions or hundreds per year?

The answer is site-specific. Aberdeen’s wind farm is small (11 turbines). Berwick Bank would be massive. Collision risk depends on turbine density, proximity to breeding colonies, flight path overlaps, and weather conditions. We don’t have enough data to predict impacts accurately for new, larger developments.

Fish: Some Winners, Some Losers

Fish responses vary by species and life stage.

Cod uses offshore wind farms as feeding grounds in summer, then migrates to spawn elsewhere in winter. Turbine foundations with scour protection provide habitat.

Sandeels—small fish crucial to seabird and marine mammal diets—are more vulnerable. They need specific sandy seabed habitats. Offshore wind farms are often built on shallow sandbanks (like Dogger Bank) because they’re easier to construct. The Marine Conservation Society warns that sandeel populations face pressure from wind farms altering sediment, plus climate change and fishing. If sandeel abundance drops, predators (kittiwakes, puffins, porpoises) suffer.

Field studies show mixed results. At Horns Rev wind farm, the three most abundant species (whiting, dab, sandeels) showed no signs of negative long-term effects. But that’s one site, one set of species, one set of conditions.

Electromagnetic Fields: Probably Fine, But…

Subsea cables carrying electricity from turbines to shore generate electromagnetic fields (EMFs). Some marine species—sharks, rays, eels, sea turtles—use Earth’s magnetic field for navigation.

Could undersea cables disrupt migration?

Current research suggests no significant population-level impacts. Studies show EMF effects are “highly localized” near cables. A small number of studies found some animals can detect EMFs, but there’s no conclusive evidence of population harm.

The caveat: “current research.” We’re adding thousands of kilometers of cables to the North Sea. At what scale does “localized” become “everywhere”?

Cumulative Impacts: The North Sea as a Test Case

Individual wind farms might be manageable. Dozens simultaneously might not be.

A 2021 cumulative impact study modeled North Sea offshore wind development from 1999 to 2050. Key finding: 2022 was the peak year for cumulative impacts from approved projects (impact score: 4.81%). But if all planned 212 GW is built by 2050, impacts increase considerably.

Most affected:

Harbour porpoises: Highest sensitivity to underwater noise and chemical contamination risks.
Seabirds (guillemots, fulmars): Barrier effects (wind farms block flight paths) impact 3.3% and 2.6% respectively.
Fish (whiting): 2.5% impact from noise.
Habitats: Sublittoral sediment faces 4.7% impacts from chemical contamination.

The study found concentrated high-impact clusters in southeastern British waters and German zones, affecting approximately 13,438 km² combined.

But this analysis is limited. It models pressures we understand. It can’t model the 86% we don’t.

What We Actually Don’t Know

Let’s be specific about the gaps:

Only 8% of protected migratory species have been studied: Most research focuses on harbour porpoises, harbour seals, grey seals, and Atlantic cod. What about minke whales, basking sharks, leatherback turtles, or the dozens of other species moving through wind farm zones?
Floating offshore wind is largely unstudied: Britain is pioneering floating wind technology for deeper waters (Celtic Sea, off Scotland). Floating platforms behave differently—they move with waves, create different noise profiles, require different mooring systems. We have almost no data on marine life impacts.
Decommissioning impacts are unknown: Turbines last 25-30 years. Then what? Do you remove foundations or leave them as artificial reefs? What are the noise and habitat disruption impacts of decommissioning? We’re building thousands of turbines without knowing how to safely retire them.
Long-term ecosystem shifts: North Sea hydrodynamics are changing. Wind turbine wakes slow water currents, potentially altering nutrient distribution, primary production (plankton), and oxygen levels. Models project local changes up to ±10% in annual primary production. How does that ripple through food webs over decades?
Interaction effects: Offshore wind doesn’t exist in isolation. Add commercial fishing, shipping, oil/gas extraction, climate change, and pollution. How do stressors interact? Does noise stress make fish more vulnerable to warming? Does habitat loss from wind farms compound overfishing?

What We Do Know (The Balanced View)

Acknowledging knowledge gaps doesn’t mean offshore wind is catastrophic. Some impacts are clear, and not all negative:

Positive Impacts

Artificial reef effect: Turbine foundations and scour protection create habitat for invertebrates and fish.
De facto protection: Trawling bans in wind farm zones reduce fishing pressure, benefiting some species.
Some species benefit: Cod, certain crustaceans, and benthic species show positive responses to turbine structures.

Negative Impacts

Construction noise harms marine mammals: Pile driving causes avoidance, potential hearing damage, and behavioral disruption.
Seabird collisions: Depends on site, species, and turbine density, but can be significant for vulnerable populations.
Sandeel habitat disruption: Crucial prey species face habitat alteration on shallow sandbanks.
Barrier effects: Large wind farms may block migration routes or force energy-expensive detours.

Unclear/Context-Dependent

Displacement effects: Some animals avoid wind farms (guillemots, porpoises). Is that avoidance harmful or just behavioral flexibility?
Electromagnetic field impacts: Likely localized and minor, but cumulative effects at scale unknown.
Ecosystem-level changes: Changes to water flow, nutrient distribution, and primary production are being observed but long-term consequences unclear.

The Honest Assessment

86% unknown does not mean 86% harmful. It means we’re making decisions with insufficient data.

Offshore wind is not killing the North Sea. Overfishing, pollution, and climate change are far bigger threats to marine ecosystems. Offshore wind is part of decarbonization, which marine life needs (ocean acidification and warming are catastrophic).

But we’re deploying infrastructure at industrial scale in one of the world’s most ecologically important seas, and we don’t understand most of what it does.

Compare this to nuclear. When Britain builds Hinkley Point C or Sizewell C, the site is 175 hectares, impacts are localized, and we’ve studied nuclear’s environmental effects for 70 years. Offshore wind is 95 GW spread across thousands of square kilometers of seabed, with new technologies (floating platforms), in a dynamic ecosystem we’re still discovering.

The question isn’t “Should we stop offshore wind?” It’s: “Should we slow down enough to answer basic questions before we commit to 212 GW by 2050?”

What Needs to Happen

The Plymouth Marine Laboratory researchers were clear: we need data, fast. Here’s what that looks like:

Mandatory long-term monitoring: Require wind farm operators to fund independent research for the full turbine lifecycle plus 10 years post-decommissioning.
Standardized assessment protocols: Current environmental impact assessments vary wildly in quality. Create UK-wide standards for cumulative impact modeling, species monitoring, and data sharing.
Before-after-control-impact studies: Compare marine life abundance and behavior at wind farm sites before construction, during operation, and after decommissioning, with control sites nearby.
Focus on knowledge gaps: Prioritize research on:
- Migratory species beyond harbour porpoises and seals
- Floating wind farm impacts
- Decommissioning ecological effects
- Cumulative impacts across multiple developments
- Long-term ecosystem shifts (hydrodynamics, primary production)
Adaptive management: If monitoring shows harm, require mitigation. If populations decline, pause new developments in affected areas until causes are understood.
Transparency: Make all environmental monitoring data publicly available. Let independent scientists analyze it.

The Path Forward

Britain needs offshore wind. We also need honesty about what we don’t know.

The North Sea is not an empty space to fill with turbines. It’s a working ecosystem supporting commercial fisheries, tourism, carbon storage, and biodiversity. Those services have value—economic and ecological.

We can build 95 GW of offshore wind by 2030. We can also study what it does, mitigate harm, and adjust course when needed. Those aren’t conflicting goals. They’re both requirements for responsible energy policy.

Right now, we’re building faster than we’re learning. That’s a choice. It doesn’t have to be.

Sources

This article is based on research from:

Plymouth Marine Laboratory (2024) - global offshore wind ecosystem services analysis
The Crown Estate Offshore Wind Report (2024) - UK capacity and pipeline data
UNEP-WCMC (2024) - marine migratory species review
Nature Scientific Reports (2021) - North Sea cumulative impact assessment
RSPB evidence submissions on Berwick Bank offshore wind farm
Scottish Seabird Centre and BTO research on seabird collision avoidance
NOAA Fisheries and Tethys database on marine life impacts
Marine Conservation Society on sandeel populations
Academic literature on electromagnetic fields, noise pollution, and fish responses

All data traced to primary sources, all citations verified where possible. For full methodology, see our Editorial Standards.