Dangers of wind turbines

A few weeks ago I wrote an introduction to a few of the renewable energy options our planet had, and concluded that wind power seems to be the most popular and widely implemented of them. As wind farms continue to grow and spread, however, bird and bat fatalities are rising with them. 

This trend is particularly prevalent with migratory species, which have their set routes that they have used year or year, and continue to do so even with rotor blades in their way. Cryan and Brown, 2007, looked into the causes of the fatalities in bat species, and concluded that the most deaths occur during the autumn migration. The bats choose to travel when there is low moon illumination and wind speeds but high cloud coverage and so when these conditions arise the death toll rises.

Graph from Cyran and Brown, 2007, showing the peak in fatalities during the autumn months.

However, as always in life, there are exceptions to the rule. A study by Arnett et al in 2008, in which they amassed data from 21 reports from the USA, also found a peak in bat deaths in autumn. Yet they also found a pattern of female deaths in May and June. Interestingly although the US Federal Aviation Administration had floodlit some wind farms in a bid to reduce bat and bird deaths there was no disparity found in fatality numbers between these lit sites and unlit ones.

Kuvlesky et al, 2007, examined wildlife impacts as a whole from wind farms, not just in flying species. They found that even worse than the turbines themselves were transmission lines and roads associated with the infrastructure, because they lead to habitat fragmentation which can harm species populations, and also allow invasive species easy access to habitats not their own. This can bring in disease and competition for resources which the native wildlife may not be able to cope with. Exotic plants spread particularly well alongside roads, unlike small mammals and reptiles which find it hard to cross them safely. The power lines also obviously pose a risk of electrocution for flying organisms.

In summary, we know where the problems arise: generally in migratory paths during autumn for birds and bats. Could wind turbines could be turned off when the optimum conditions of bat flight coincide with these known migration times? It is of course possible, although economically that may not be the standpoint we humans decide to take. A future precaution that could be implemented would be to study and record migratory paths more thoroughly, and purposefully not place wind farms in them.

For wildlife as a whole it is the ground habitat disruption which is causing the most problems. Some measures can be taken to alleviate this, highlighted by Kuvlesky et al. Simple changes such as putting wind farms on agricultural land as opposed to native lands can help reduce the biodiversity loss. More research needs to be done onto the impacts of biodiversity as so far the focus has been on birds and bats.

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