Losing cover of darkness

Species that rely on darkness to forage and feed are losing the gift of camouflage thanks to advances in the lighting used to illuminate the world's cities and coastlines, a study has shown.

The worldwide proliferation of energy efficient broad spectrum lighting has the potential to disrupt an array of visually guided ecological processes.

New research has demonstrated that these new lighting technologies can significantly improve a predator's ability to discriminate prey species against a natural background.

The magnitude of this effect varies depending on an organism's colour, meaning certain colour variations may be at greater risk.

The study, published in the Journal of Applied Ecology, was conducted by researchers at the University of Plymouth and Plymouth Marine Laboratory (PML).

It is one of the first to examine the potential for artificial light at night (ALAN) to affect the camouflage mechanisms of coastal species.

Oak McMahon, who led the research while studying for an MSc in Applied Marine Science and is now a PhD candidate at the University of Plymouth, said:

"This study clearly indicates that new lighting technologies will increase the conspicuousness of prey species by reducing the efficacy of their camouflage. Our findings revealed that species of Littorinid snails found commonly on our coastlines will remain camouflaged when illuminated by older style lighting. However, when illuminated by modern broad spectrum lighting, they are clearly visible to predators and at far greater long-term risk as a result."
With estimates indicating that 23% of the world's surface between the planet's polar regions is affected by ALAN - and a rate of increase of 2.2% between 2012 and 2016 - the need to address the situation is pressing to say the least.
In the study, the researchers highlight a variety of mitigation methods available to planners and environmental managers when considering its ecological impacts.
These include reducing the amount of light used, shielding lights to reduce their effects on the surrounding environment, employing part-night lighting during times of peak demand, and manipulating the spectra of lighting to minimise ecological impacts.
The researchers highlight that while it may seem intuitive to suggest using narrow spectrum lighting to avoid these impacts, the effects of ALAN extend beyond those seen on camouflage and that all parts of the visual spectrum will likely have some ecological impact.
Street lighting creates an artificial glow in the night sky above Plymouth and the surrounding areas (Credit Thomas Davies, University of Plymouth)

Street lighting creates an artificial glow in the night sky above Plymouth and the surrounding areas (Credit Thomas Davies, University of Plymouth)

The activity highlighted here is funded by the Natural Environment Research Council (NERC)

NERC is the UK's main agency for funding and managing research, training and knowledge exchange in the environmental sciences. Our work covers the full range of atmospheric, Earth, biological, terrestrial and aquatic science, from the deep oceans to the upper atmosphere and from the poles to the equator. We coordinate some of the world's most exciting research projects, tackling major environmental issues such as climate change, environmental influences on human health, the genetic make-up of life on Earth, and much more.

NERC is part of UK Research & Innovation, a non-departmental public body funded by a grant-in-aid from the UK government. www.ukri.org

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