International SEEDS Conference 2017: Sustainable Ecological Engineering Design for Society 
Healthy Environments, Buildings and Spaces: Current position and future models
Leeds Beckett University, UK – 13th and 14th September 2017

Let there be darkness

LED security lights effects on trees and green city landscape:
Human and wildlife circadian rhythms, mental well-being, road safety and the view of our night sky
David Garlovsky, BSc, MSc, Certificate in Social Phenomenology


There has been a growing trend for urban areas in UK, USA and elsewhere to change roadway and residential street security lighting to high pressure sodium [HPS] and blue-rich LED lights often without health or environmental impact assessments. Studies [e.g. WHO] have shown blue-rich LED lights affect human health well-being and other studies showing effect on wildlife circadian rhythms, road safety and view of our night sky for astronomical observations. It has been long established that access to green space improves our mental well-being.

This is not a newly discovered problem. Botanists were aware of the deleterious effects of incandescent street lighting on trees eighty one years ago by Matske in 1936, while horticulturalists became aware as result of research forty two years ago by Cathey and Campbell in 1975; with harmful effects on both wild and domesticated plants.

Research in 1974 by Royal Society of Birds Chicago branch and Chicago District 14 Environmental Education Project was ignored with the City installing HPS on residential streets primarily based that they were more energy efficient yet 11% after 13 months failed. There were effects on young trees with 60 percent of a group of saplings suffering death or damage to growth over their first spring and summer.

Soy bean farmers learned not to plant in a field adjacent to HPS roadway lighting. The nighttime illumination can reduce crop yield by 20 to 40%. (Chen et al. 2009)

Research has shown that making choices about the kind of lights we use, simply on the basis of energy consumption may be shortsighted. Energy saving measures need to be linked to health and ecology considerations such as the presence of heavy metals in LED’s in their manufacture.

Local authorities should consider the potential impacts of installing blue rich street lighting. In the UK, Public Health England are recommending that councils use a warm colour temperature for street lights to minimize glare and discomfort. Street lighting should be tested ‘in situ’ before a lighting scheme is rolled out to ensure that it is the minimum required and does not cause harm to human well-being, trees and wildlife. It is crucial for local communities be more involved in deciding how streetscapes including trees and lighting are planned, managed and maintained.