Unless you are from Gotham city, you might be not aware of the importance of bats in our lives. And commute to work in a brand new trunk road might be more harmful than you think.
Bats. Those little creatures, commonly known as 'flying mice' or 'glabrous mice' in some cultures, do not usually receive enough credit compared to other mammals. Often viewed with suspicion and associated with sinister stories due to their favour of darkness, they have a crucial role in the control of insects populations, especially those detrimental to humans and related activities.
But a happy bat needs specific conditions to prosper: their delicate nature requires a habitat where adequate roosting, foraging and commuting routes are guaranteed to ensure survival. Bats are loyal to their roosts even over generations! Unfortunately, environmental impacts of lights, noises and landscape changes due to cities expansion have caused the loss of many colonies over the years. Nowadays, bats are among the endangered animals in Europe and officially protected by the EU directives about habitats preservation; today, in the UK, all the four local species are at risk of extinction.
There is a lot of disinformation about bats. Those mammals are the most effective and harmless insecticide in the world: a single adult can devour millions of insects during its lifetime, a force of nature that planet earth 'uses' to preserve balance.
Studies found out that roads have a significant negative impact on the bat population, as they act as a barrier that restricts the availability of commuting routes and foraging options. The reason lies in the fact that the little animals use echolocation to build up a sonic map of the immediate surroundings, so they rely on the terrain and vegetation to navigate the environment. That make roads a dangerous space to cross, while lights and noises affect the ability to correctly 'interact' with preys. The consequent isolation of the roosts causes the rising of inbreeding and premature deaths; in fact, a decrease of bat diversity has been observed from 1 to 6 kilometres from roads.
Several solutions have been tested to address the problems, with different degrees of cost and time efforts: among the mitigation strategies to overcome the 'barrier effect' there is the construction of underpasses or 'hop hovers'. The latter is created by planting trees of increasing height as the road approaches and, possibly, having the branches from one side extended to the other to minimise gaps and let bats cross safely. The success of those solutions varies and depends on local conditions; a proper bridge, purposely designed for wild animals, was constructed in 2009 in Cornwall at the cost of 300.000 £: unfortunately, the following monitoring campaign proved that bats rarely used it.
Nevertheless, some inexpensive solutions might be implemented in the design of new roads, for example switching off or dime lights during the night, where human activities are at the lowest and bats at the highest. However, further actions and design practice standards will be necessary soon to reverse the current trends and protect those essential little allies of ours.
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