LEE Ee Meng Kenneth, Life Sciences Major – AY 2017/2018
The switch to LED lighting – ecological impacts on bats in Singapore
One of the most stereotypical abiotic changes in cities is the increase in artificial light at night (ALAN) – indeed, maps of ALAN captured by satellites reveal the locations of settled areas and are used as urbanisation gradients on a global scale. And its ecological impacts are reasonably well-documented. There is at least one entire book on the topic, and certain issues are familiar to many people. One is the fatal attraction of insects to lights. Many nocturnal insects, notably moths and mayflies, exhibit positive phototaxis – they orient toward light. As to the mechanism that explains why they swarm to artificial ones – it remains elusive. Regardless, this phenomenon can have cascading effects, for example on aerial insectivores.
That said, most knowledge of ecological impacts relates to traditional lighting technologies. However, private and public agencies around the world are replacing traditional (often high-pressure sodium; HPS) outdoor lights with LEDs. Now, LEDs offer clear advantages over HPS lights. Like, better visibility and safety, longer lifespans, reduced energy consumption and lower carbon footprints of manufacture. With outdoor lighting contributing meaningfully to the carbon footprints of cities and the urgency of the climate crisis, such retrofits are environmentally responsible. But there’s some concern about (and little knowledge of) the ecological impacts of LEDs. So, as retrofits proceed apace, we’re seeing a flurry of studies. Some document negative effects on some animals, whereas others find none.