You may have heard that exposure to blue light can disrupt melatonin and therefore your sleep, but it turns out it’s also bad for wildlife.
La Trobe University researcher Alicia Dimovski in Australia is dedicated to studying how exposure to light affects kangaroos, a species of marsupial similar to a small kangaroo.
For his experiment, he exposed the animals to LED lights inside one enclosure, while in a second enclosure he turned on light-blocking blue LED lights, like the “night mode” of the phone or laptop. In a third enclosure, the kangaroos were in natural darkness. After ten weeks, Dimovski collected blood samples to analyze the kangaroos’ melatonin levels. The results are overwhelming.
the hormone of darkness
Like us, kangaroos rely on the hormone melatonin to get a good night’s sleep. The level of melatonin that is produced in our body is regulated by a light-sensitive protein in our eyes called melanopsin. When certain wavelengths of light hit melanopsin, it suppresses melatonin production. It has been seen that reducing blood melatonin levels by artificial light can alter our body’s natural sleep-wake cycle.
Melatonin is also important for the immune system. In mammals, melatonin acts as an antioxidant, capturing free radicals. Despite its potential to damage DNA and cells, the body is able to neutralize them and keep their levels low. However, when we have an infection, the body’s immune response can cause an increase in free radicals. Without melatonin, this increase in free radicals can cause oxidative stress, which increases inflammation.
blue light
Not all lights are the same, nor do they activate melanopsin equally. Blue light with a wavelength between 420-440 nanometers activates melanopsin to a greater extent, thus reducing melatonin.
As has been the case in many countries, in 2009 the Australian government began phasing out incandescent light bulbs in favor of energy efficient alternatives such as LEDs. Since then, LEDs have become the main source of light in Australian homes, businesses and street lighting. Unfortunately, low-energy light bulbs are causing health problems for nocturnal wildlife.
Cool white LED lights cause problems because they contain a lot of blue light. However, researchers found that when kangaroos were exposed to amber LED light, they had melatonin levels equal to kangaroos in natural darkness.
In addition to sleep, the change in light level throughout the four seasons is a timer for vital processes such as reproduction. Tammar wallabies have a mating season and rely on this biological clock to ensure that births occur when there is enough food to raise their young. This means that even very low levels of light pollution can disturb wildlife.
These findings indicate the importance of installing hot LED light sources in street lighting. Wild life will appreciate it.