People have very strong views about wind turbines on both sides of the debate. With several current proposals in Dorset, on land and at sea, including at Silton in north Dorset, East Stoke in Purbeck and about eight miles off the Purbeck coast, we outline DWT’s approach to wind energy proposals and some of the potential impacts on wildlife that we examine when responding.
Strong Local Concerns about wind turbines
Some of the concerns which people have about wind turbines, such as their visual impact, are not within our remit to comment on. Often DWT will be able to recommend changes to a proposal that will remove major risks to wildlife, and so we like to talk early on to developers when we have the chance.
Climate change is likely to have a significant impact on Dorset’s wildlife and measures to reduce its causes are welcomed. DWT therefore supports the principle of increasing the proportion of our energy generated from renewable sources in combination with measures to reduce energy demand overall.
Currently more than three quarters of the energy generated from wind in the UK comes from land-based installations. This will change dramatically over the next decade as new offshore wind farms with six times the capacity are planned.
Proposed wind farms on land in Dorset have been relatively small when compared to others in Britain and offshore 4 turbines are proposed at both East Stoke and Silton. Nevertheless they have attracted some stiff opposition.
Potential wildlife impacts onshore include the direct loss or damage to habitats, disturbance to species, collisions with structures, cumulative effects with other nearby proposals and positive measures like habitat creation or management. Our first consideration is whether a proposal affects an important habitat, especially recognised wildlife sites such as Sites of Special Scientific Interest or Sites of Nature Conservation Interest. Where wind farms are proposed near to valuable habitats, adequate safeguards should be built in to avoid harm. We also like to see positive land management for wildlife either under the turbines or, if more appropriate, elsewhere within the wider area.
Birds can collide with any structure, from power lines to patio windows. Wind turbines can particularly affect large species which find it harder to manoeuvre, and/or those that fly at the height of the rotating blades. In some places, such as Altamont Pass in California and south-west Spain, wind farms have been built on major migration routes and caused considerable rates of ‘bird strike’, especially to birds of prey. Bird populations should be studied for each proposal to ensure such locations are avoided.
For bats, the research is less advanced. Species that fly high and for long journeys, particularly on migration, seem to be most affected. This does not apply to most of the British species. There is some evidence that bats may deliberately investigate turbine towers, which clearly places them at greater risk of collision. Mitigation options might include avoiding routes used by ‘at risk’ species, such as the high-flying noctule, or locating turbines away from important bat foraging features. If concerns remain, turbines could even be switched off when bats are most vulnerable; as most electricity is generated in winter, whereas bats are active at night in summer, this would not necessarily reduce the capacity significantly.
It is important to distinguish between individual casualties, though unfortunate, and mortality rates that might affect populations overall.
Everything about offshore wind energy is big. The turbines are much bigger - towers the height of Big Ben with rotors the diameter of the London Eye and some of the proposals are on a massive scale, the Dogger Bank and East Anglia Array wind farms between them potentially containing up to 5000 turbines (if each zone is fully developed).
While offshore wind farms may appear less contentious than those onshore, there are still other sea uses that may be affected and possible environmental impacts associated with each stage of development.
Direct impacts occur when placing any structure on the seabed, and the construction phase of a large wind farm (the proposal off Dorset is for 180-250 turbines) can cause considerable disturbance and generate a lot of underwater noise. The cables running between the turbines and connecting to the shore will also cause disturbance during construction and the effects of electro-magnetic fields on some marine organisms are not yet understood.
As on land, the biggest concern is often the potential impact on seabirds and migratory birds, either from direct collisions with the rotor blades or indirect effects such as loss of feeding or roosting areas. Much research has gone into understanding these impacts and how they can be mitigated.
Effects on marine mammals are most likely during construction and decommissioning (and perhaps during exploration), with disturbance and noise pollution being the main concerns.
An intriguing aspect of offshore wind farms is the potential for ecological benefits through habitat enhancement or protection. The structures placed on the seabed will act as artificial reefs, providing a habitat for rock-dwelling species and shelter for mobile species. This will benefit some species (possibly including commercially valuable species such as lobster) but needs to be weighed against the value of the habitat replaced and impacts on ecological balance, for example by creation of predator shelters in a previously open space.
Potential habitat protection might result from turbines obstructing mobile fishing gear and it has been suggested that wind farms could be located within Marine Protected Areas (MPAs). It remains unclear whether it is a good idea to create MPAs (which are generally designated to protect natural features) inside such large scale developments.