"Dark sky friendly" pitfalls

"Dark-sky friendly" is a term one hears increasingly in different parts of society as more people become aware of the problem of light pollution and want to do something about it. Typically used in the context of outdoor lighting products and installations, the idea that lighting can be "friendly" toward dark skies is alluring. It implies that we can have our cake and eat it, too: with the right characteristics, outdoor lighting can be made harmless to the nighttime environment.

However, as many a conservation expert will tell you, the only 'dark-sky friendly' outdoor light source is the one that was never there in the first place. Outdoor artificial light at night is a tremendous environmental challenge whose significance is really only now fully — pardon the pun — coming to light. At the same time, outdoor lighting in human culture is here to stay, as it helps extend the work day, ensures safe transit at night, and enables a nighttime economy. How can we best balance these competing needs?

While no light source in an outdoor setting is truly 'friendly' to the night sky, there are approaches to lighting design and product selection that significantly reduce the impact of that lighting to the nighttime world. Here are a few of the considerations that can help individuals and organizations avoid falling into the 'dark-sky friendly' trap.


Buying outdoor lighting products labeled "dark sky"

Let's face it: lighting is confusing. The mass of technical terms on product packages and in consumer information, from lumens to Kelvin, is a jargon that most of us don't understand. Many engineers and architects know relatively little about lighting, but they are routinely asked to include exterior lighting in building or landscaping plans. Government officials, tasked with making decisions about how outdoor lighting is to be regulated, often know less than engineers. And as is often the case when presented with choices about technical matters, we defer to those we perceive to be experts in those subject areas.

While there are now many competent lighting designers who understand how to minimize light pollution from outdoor lighting installations, property owners and developers often do not contract their services. Instead, whether to save money, time, or both, lighting selections frequently depend on marketing materials provided by manufacturers and distributors of outdoor lighting products. But here's the catch: no one owns the term 'dark sky'. Since it is not a registered trademark, any lighting manufacturer can brand lighting products with variations on 'dark sky', no matter what the performance specifications of those products. And there are many examples of lighting products bearing such labels that arguably do little, if anything, to protect the night sky.

According to the old saying, "knowledge is power", and there's no substitute for educating oneself properly in order to make better decisions about outdoor lighting. Some basic information about lighting principles is sufficient to evaluate the suitability of outdoor lighting products to meet your site's needs while not unnecessarily polluting the nighttime environment. These basics include:

• Shielding and direction: is the product designed to prevent light from being emitted directly into the night sky when it is installed and used correctly? Will the light trespass onto neighboring properties?
• Light distribution: is the way the light spreads out once it leaves the product adequate for your needs? Does it offer too much light, or too little?
• Spectrum: what color is the light? Does it have a "warm" or "cool" appearance? Does it limit the amount of blue light emitted? (which we know to be most harmful to the nighttime environment)
• Controls: does the product include any features that allow the user to adjust the brightness of the light or the amount of time it is on?

Pro tip: Learn a little about lighting characteristics to help evaluate manufacturer claims about the 'dark sky friendliness' of their products. Also, look to organizations like the International Dark-Sky Association for guidance, and in particular see the product listings that are part of its Fixture Seal of Approval program. That way you can be confident that lighting products you choose will truly minimize the impact of outdoor light at night on the nocturnal environment.


Failing to look at lighting projects holistically

In the previous section, we identified a few important characteristics of outdoor lighting products that determine how much a given product might affect conditions on the ground and in the night sky. They are suggested as a group, because considering any one element in isolation from the others can result in a poor outcome. A property owner can install beautifully shielded outdoor lights that are too bright, too blue, and are on when no one needs the light. Or, to use a different example, concern for wildlife might dictate a very warm light color, such as amber, but could result in the installation of unshielded light that exposes plants and animals to light unnecessarily all night long.

But let's take a step back and ask a more basic question: is light needed in the first place? We often gravitate toward installing outdoor lighting on building exteriors and in other contexts by default, but far less often do we try to figure out why we want it. Does it make us feel safer? Are there legitimate safety concerns around structures at night to which lighting can help alert users of those spaces? In many cases, fair evaluation of these questions might lead to the conclusion that lighting isn't needed at all. Perhaps other non-lighting techniques, such as the use of luminous pavements or reflective paints, can get the same job done as effectively (or even more so).

Once we establish a clear need and function for outdoor light at night, the next set of questions has to do with the utility of that light: How much light is needed? Where should the light be positioned? What can be done to limit the amount of light used to prevent waste? In many cases, these decisions can be made without the assistance of professionals. However, once the decision to light is made, it is often true that the best implementation of that decision benefits from the advice of an experienced lighting designer.

Pro tip: When considering site lighting, whether for new construction or as a retrofit to an existing installation, start by determining the real need for outdoor light at night. Factors such as occupancy times, amounts of foot and vehicle traffic, and the expected uses of outdoor spaces should all be taken into account. To provide the greatest benefit to users of those spaces, keep in mind all of the main characteristics of lighting — shielding, distribution, spectrum and controls — in choosing how to light. And don't forget that there are non-lighting methods that may meet all of your site requirements that may save additional money.


Expecting too much too quickly

Sometimes when we do the right thing about a problem, the full consequences of making the right choice aren't immediately obvious. And sometimes we never see the results directly, even if we have good reason to believe that making the right choice positively benefitted the situation. But there can be power in numbers. Skipping the daily drive to take the bus to work might not clear the air over your city, but if many people adopt the same practice, the change will come over time. The idea that the sum of little changes adds up to something big is the philosophy behind the old slogan of the environmental movement: "Think globally; act locally."

The same is generally true about the connection between outdoor lighting choices and the health of the nighttime environment. A property owner or land management agency that makes changes to outdoor lighting might not see any change to the quality of their night sky, and from this conclude that the effort was a failure. Quite the contrary! We have good reason to believe that every change made to outdoor lighting with the night sky in mind benefits the nighttime environment, no matter how insignificant the change may seem. One less photon of artificial light entering that environment is one less photon to distract a migrating bird, one less photon to lead a pollenating insect away from its work, and one less photon to brighten the night sky and make it difficult to see the stars.

To make the kind of difference noticeable to the human eye takes a lot of effort distributed across society. We are making those gains, slowly. The key to balancing enthusiasm for making a difference with the apparently glacial pace of change is to set your expectations appropriately. Know that you're making a difference even if it's not obvious. And that doing the right thing by implementing good outdoor lighting plans makes an example of your effort that may encourage others to follow your lead. Success builds on success.

Pro tip: To find out where your dark-sky efforts fit into the context of your surroundings, consider measuring and monitoring the quality of the night sky over your site. Following sky quality changes over time can help identify particular contributions from light pollution that are brightening your night sky, which can suggest targets for outreach to reduce their influence.


Do you have a project coming up that involves outdoor lighting, but you don't know where to start with planning for dark-sky preservation? We can help you devise a site lighting plan that meets all of your needs while limiting the effect your project will have on the nighttime environment. Contact us today!