The impact of floodlighting on wildlife

As discussed in some of our previous blogs, LED floodlights offer significant benefits from a sustainability perspective. Not only do LEDs use far less power than gas-based equivalents, for instance, but the longer lifespans and lower maintenance requirements associated with LED technologies also help to ensure that the overall impact on the environment is much smaller too.

The environment is an issue that extends beyond the subjects of carbon emissions and material consumption, of course. When evaluating the true environmental impact of floodlighting, we must also consider the ramifications on wildlife. That is because, like any man-made technology, lighting can have a pronounced influence on the wellbeing and behaviours of animals.

In this post I would like to explore floodlighting’s relation to wildlife, specifically those species that it is most likely to affect, and the actions that can be taken to minimise or negate that impact. Before reading, please be aware that the issues outlined below are not specific to LEDs and – in some cases – relate to artificial lighting more generally, not just floodlights.

Birds

Birds of all kinds migrate from one location to another, typically to find either new sources of food or new nesting locations. Migratory behaviours can vary from short-distance, where birds will move to a new location within their current vicinity, to long-distance journeys that measure in the tens of thousands of kilometres. For certain species, migration is a predominantly nocturnal activity.

Light pollution – which a poorly designed floodlighting system can contribute to – can have serious repercussions for migrating birds. Artificial lights can be mistaken for extended daylight, leading birds to set off on their journeys earlier than they normally would. Upon arriving at their destination, a flock can then find that their new environment does not yet contain the natural resources they need to survive.

Particularly brightly-lit areas can also cause disorientation in certain bird species, leading them to circle aimlessly instead of continuing their journey. Exhausted, those birds may then collide with buildings, or fall prey to urban predators such as cats and rats

Mitigating the impact of floodlighting

The main issue here is one of design. Light shields and well-designed optics – like those incorporated into Midstream’s own floodlights – ensure that the majority of the light emitted by a floodlight is directed at the desired target. Not only does this improve uniformity and visibility within the floodlit area, it also helps to minimise the spill of light into the local environment.

Sea turtles

The disorientating impact of bright lights doesn’t only affect avian species; it also presents a danger to new-born sea turtles too.

The annual reproductive cycle of sea turtles sees them seeking out sandy beaches on which they can lay their eggs. While this activity itself isn’t typically impacted by floodlighting, a hatching turtle’s immediate instinct is to head towards the strongest source of light. Whereas that would normally be the moon, thus leading them straight to the ocean, bright lighting can instead cause them to head further inland.

As is the case with birds, this ultimately leads to exhaustion, and puts the hatchlings at risk of dehydration, predators, and hazards such as roads too. Estimates suggest that, in Florida alone, more than 100,000 new-born sea turtles die each year due to light-related disorientation[1].

Mitigating the impact of floodlighting

Light spill is a critical consideration once again here. Light shields and optics that help to direct light are important, as is installation height, with shorter masts serving to prevent light from escaping. Naturally, this latter solution may not be possible in all scenarios.

The other factor here is that of light spectrum. Amber and red light has been shown to have less of an impact on hatchling behaviours, and so LEDs tuned to produce less blue light can be extremely beneficial. Unfortunately, the performance of monochromatic orange light of this kind is typically worse, which presents challenges of its own.

These complexities, in tandem with the fact that marine environments are now highly regulated and controlled, ensure that it is essential to seek out expert guidance for coastal lighting systems.

Bats

Whereas lighting’s impact on birds and turtles relates to specific activities like migration and hatching, for bats the consequences are much broader. As nocturnal animals, bats attempt to avoid light wherever possible, with daylight hours normally exposing them to natural predators like sparrowhawks.

Artificial lighting, floodlights included, can cause significant behavioural changes in bats. Too much light can cause bats to leave their roosts later than normal, for instance, which in turn prevents them from finding adequate food supplies since many insects have returned to their nests. Some bats may even refuse to leave their roosts at all if the surrounding light is too strong.

Because artificial light attracts insects, it can also serve to draw food away from a bat’s usual foraging ground. This is a particular problem for slower-flying species such as myotis (mouse-eared) bats, which will avoid lit areas altogether.

Mitigating the impact of floodlighting

Of the UK’s 17 breeding bat species, four are currently listed as being at risk of extinction. As a result, and as is the case in many other countries, bats and bat roosts are extremely well protected by government legislation. In most instances, regulation prohibits roosts from being disturbed, which includes “reckless” or “intentional” disturbance as a result of light spill.

In the UK, the most recent guidance around this subject comes from the Institute of Lighting Professionals’ 2018 note on artificial lighting. As explained in this document, one of the major advantages of LED lighting is that it offers greater control over issues like light spill and colour temperature, both of which can have an impact on bats’ well-being.

Nonetheless, the specific circumstances around bats and lighting remain complex, and should only be approached with the support of experienced professionals.