ecology of light

Ecology of Light with Travis Longcore

I am coming to you with this episode about L I G H T. Natural light from the sun is so vital to the health of every living thing. Light energy affects temperatures on land and water, biological processes (such as the relationship between predators and prey), plant photosynthesis and growth.

While I am an early riser already, I have taken to getting up for the sunrise and staring at the purple and reds and oranges at sunrise over Puget Sound. We all need more purple. I repeat. We need more purple in our life. Even ecologists. Yes, especially urban ecologists. Dawn’s first light kicks off a chain of physiological actions in every cell in our bodies. Then Darkness cues our brain to release the melatonin that lulls us to sleep, setting off more actions that keep us alive—changing hormone levels, and even turning on and off various genes.

Unfortunately, the latest statistic is that we (United States) spend 93% of time indoors not exposed to natural light from the sun. In order to see, we turn on artificial light, which is not neutral, during the day and at night. In starting this podcast, this is something I am keenly aware of. It is not really an outdoor activity, so I am striving to balance indoor interviews, editing, etc. with outdoor time professionally, recreationally and even have some ambition to do some interviews and recording outside as much as possible. We should strive for a better balance between indoor life under artificial lighting and getting outside and all the nature-related benefits I have talked about in episodes with Kathy Wolf and Julia Plevin.

To bring some street credibility to the conversation about the ecology of light, my guest on this episode is Dr. Travis Longcore. He is going to “illuminate” this topic of the ecology of light, especially focusing on astronomical, ecological and human health impacts of artificial light at night. I know Travis from my days working in SoCal restoration on a project to save a dime-sized beautiful, yet endangered blue butterfly. He is now an Associate Adjunct Professor at the UCLA Institute of the Environment and Sustainability. Travis also serves as Science Director of The Urban Wildlands Group, a Los Angeles-based conservation nonprofit, and he is also an independent ecological design and environmental policy consultant. Travis co-authored a 2004 article “Ecological light pollution,” which is the most read article of all time at Frontiers in Ecology and the Environment. This seminal piece of research has been key to jumpstarting an emerging field of ecology focused on artificial light’s effect on living things. A couple times a week Google Scholar blows up my email with new literature citing him or related research, such as:

Effects of a power plant closure on home ranges of green turtles in an urban foraging area

Does changing to brighter road lighting improve road safety? Multilevel longitudinal analysis of road traffic collision frequency during the relighting of a UK city

But light pollution doesn’t just affect human health; the loss of darkness is linked to increased energy consumption and disrupted ecosystems and wildlife. Some problems with artificial night lighting are widely known such as the disorientation of sea turtle hatchlings by beachfront lighting. Plants have photreceptors and light at night influences phenology. It can mess the migration of birds and salmon. We barely see stars at night the city, let alone the suburbs anymore. Light pollution is key 'bringer of insect apocalypse' says a Guardian article from Nov 2019. Artificial lights are a deadly attraction for insects, which impacts all animal and plant species that rely on them for food and pollination. Lastly, a portion of outdoor light is unnecessary costing us billions annually meanwhile releasing millions tons of C02 a year

You may or may not have strong thoughts about light, but we all have feelings about dark. If you live in an urban area, many of us take artificial light at night as a given and don’t give it a second thought. We may take it for granted. Some may enjoy the city lights – think New York, Vegas…and Travis will talk about Chicago as and example. You may correlate dark urban areas with crime. Have you checked out your Nextdoor feed lately (aka the Twitter for old people) – I had to bail on it a few years ago. Eyewitness reports of someone walking down my alley, or driving an unmarked vehicle down the street along with pleas to be on the lookout for lost pets and solicitation for lawn care. I couldn’t believe we live in the same neighborhood! My point is that our fears about darkness can be socially constructed. Lighting up private space, or public space for that matter, doesn’t necessarily make us immune from crime. Anyway, I know too, that my conception of personal safety is much different as an older white guy who is used to running urban streets and walking through urban forest all the time. Its complicated, and I think Travis is going to help us unpack some issues related to light’s impacts on ecological health as well as cultural considerations and economic ramifications of our access to lighting at our beckon call.

After listening to this episode, you should consider taking a stroll at dusk or after dark – with a buddy – in your closest greenspace and observe how lights from the street, nearby homes and business may affect the ecology of that space. Meanwhile, novel packets of info is about to flow into your ears from my conservation with Travis Longcore. We talk about:

  • the latest on the Palos verdes blue butterfly

  • origins of the research behind light pollution

  • classes of impacts from lighting, such as orientation/disorientation, predator/prey relationships, and disruption of circadian/circanial rhythms.

  • distinctions between astronomical light pollution, which affects our ability to see the stars & ecological light pollution which affects ecosystems

  • patterns of light and dark and biological timing about how animals and humans fundamentally respond

  • how we measure brightness of light and considering how bright of light we need

  • the economic and emotional reasons that artificial lighting has become so pervasive in our society

  • arguments for smarter and better lighting

  • and examples of towns and cities getting it right


You can find out more about Travis by visiting his website And more about the Urban Wildlands Group at

Thanks for the Seattle band Dumb Thumbs for providing the theme song. You can find all of their tunes at

Thanks for listening. Thanks for subscribing. You all are the best. We hit 1000 downloads a few days ago! I’d love to keep it going, so tell a few friends about the show and follow the podcast on Instagram and Twitter @treehuggerpod.

Until next time. See you in the forest.