Bat safety has long been a concern for environmentalists when it comes to wind energy turbines. The animals believe them to be trees and search for a roosting spot, but end up flying into spinning blades. Huge numbers of bats are still dying at wind farm sites, especially in America's Great Plains and the Canadian forests, where populations are naturally large.

Last year in America, the AWEA - the wind energy industry's trade body - announced that it would be releasing voluntary guidelines that would prevent the problem by introducing low turbine speeds at times of day when bat colonies are naturally at their most active, and green groups strongly supported the measure.

However, many conservationists believe that the measure still fails to achieve its intended aim. They say that if the blades could be slowed further at key times, bat deaths could be reduced by at least 90pc, rather than the current anticipated target of 30pc, without compromising on overall electricity production. The wind energy industry disputes these figures, however, and the guidelines are yet to be adopted.

Bats are vital to the ecosystem because of their insect-rich diet. This saves the agricultural industry billions of dollars annually in insecticides and pest control.

Many believe that the voluntary guidelines are a crucial first measure to address the problem but that further measurable progress will be needed, as bats are slow to reproduce and have long lifespans. Their populations are therefore slow to recover from big losses.

The challenge will be for conservationists, scientists and energy producers to find the sweet spot between optimum animal safety guidelines and the needs of energy production. The situation is a difficult one for a world looking to become increasingly green and sustainable.