Protect wildlife with LED lighting
One thing that hasn't changed even though people are not outdoors is the outdoor lighting that has been installed to facilitate nighttime human activity. If there is any movement in my neighbors, the lighting will continue to work even when no one is around. Artificial lighting disrupts the behavior, injures and even kills thousands of birds, reptiles, invertebrates and mammals each year. Recognizing that there is no substitute for a naturally dark environment, there is a growing body of research on how to achieve lighting that meets human needs while minimizing adverse effects on animals.
The inherent differences between human visual responses and animals' behavioral responses and visual sensitivities open the door to the identification of outdoor lighting spectra that can minimize harmful effects on wildlife while still providing adequate lighting for humans. A research article titled "Rapid assessment of lamp spectrum to quantify ecological effects of light at night" provides insights to predict spectral power density of various lighting products (SPD), which led to the widespread adoption of LED lighting on wildlife.
The study analysed the effects of 24 artificial light sources (various lighting technologies, including LEDs) on the behavioural, visual acuity and physiological responses of insects, sea turtles, shearwaters in the Newell area and juvenile salmon for four parameters. Effects: Correlated Color Temperature (CCT), Color Rendering Index (CRI), glow and melatonin suppression (blue light content). Of these parameters, the CCT appeared to have the strongest correlation with effects on wildlife, and in general, the CCT was warmer, so the use of cooler CCTs had less adverse effects on the studied species. This conclusion has important implications for LED lighting installations because, unlike conventional lighting technologies such as low-pressure sodium, the SPD of LED products can be tailored to specific applications.
There is a drawback to using CCT as the only metric to assess potential impact, since light sources with significantly different SPDs still have the same CCT. Therefore, different predictors have been suggested, including the percentage of visible light below a given wavelength threshold, the dehormone response in humans (defined as the increase in irradiance from the test light source by intrinsically optically active retinal ganglion cells compared to the standard D65 light source) the percentage difference in sensitivity), and the ratio of melatonin to bright light (M/P).
Other studies on the same four animal populations concluded that while melatonin response and M/P metrics were generally most useful in predicting impacts on wildlife, CCT appeared to provide better predictions for insects value. This again has particular implications for LED lighting, as the use of shorter wavelengths in the violet range allows the light source to optimize melatonin response and M/P ratio, while still avoiding the blue light associated with poor melatonin responses in humans. However, this violet light is so attractive to insects that normal behavior is disturbed, as shown in Figure 1.
While research into the effects of artificial lighting on specific species is underway, the bottom line to keep the controversy to a minimum is clear: low-CCT lighting, while straightforward and simple, is not a one-size-fits-all solution. In addition to proper CCT, the project must also emphasize timing, intensity and distribution, i.e. providing light only when needed, at the required intensity, and only where it is needed.
Many LED-based outdoor lighting projects designed with these principles in mind have recently been implemented. One of the most well-known negative impacts of artificial lighting on wildlife is turtle hatcheries. After turtles emerge from their nests in sea sand where they lay their eggs, they are drawn back to the sea by the moon's reflection on the surface. But artificial light It is easy to disorient hatchery turtles, often resulting in their death.
A newly installed LED lighting solution on the Gulf Coast of Alabama is an example of mitigation measures that can be taken (Figure 2). The pole lighting on the shoreline has a circular shield on top (for dark sky considerations) and an additional semi-shield that directs light away from the sea. Additionally, the LED lighting is low CCT amber, distinguishable from the cool white of the moon. The other lighting installations focus on the health of birds, bats and even polar bears, each using LED products with an output spectrum specifically chosen to minimise harmful effects.