Those lights aren’t just messing with your sleep. They’re bothering the trees.

Read the full story at Anthropocene.

Like humans, trees have circadian clocks. A new study finds urban light pollution changes those clocks, causing trees to leaf out earlier and change color later.

Light pollution is disrupting the seasonal rhythms of plants and trees, lengthening pollen season in US cities

Some cities never sleep. Noam Cohen/EyeEm via Getty Images

by Yuyu Zhou, Iowa State University

The Research Brief is a short take about interesting academic work.

The big idea

City lights that blaze all night are profoundly disrupting urban plants’ phenology – shifting when their buds open in the spring and when their leaves change colors and drop in the fall. New research I coauthored shows how nighttime lights are lengthening the growing season in cities, which can affect everything from allergies to local economies.

In our study, my colleagues and I analyzed trees and shrubs at about 3,000 sites in U.S. cities to see how they responded under different lighting conditions over a five-year period. Plants use the natural day-night cycle as a signal of seasonal change along with temperature.

We found that artificial light alone advanced the date that leaf buds broke in the spring by an average of about nine days compared to sites without nighttime lights. The timing of the fall color change in leaves was more complex, but the leaf change was still delayed on average by nearly six days across the lower 48 states. In general, we found that the more intense the light was, the greater the difference.

We also projected the future influence of nighttime lights for five U.S. cities – Minneapolis, Chicago, Washington, Atlanta and Houston – based on different scenarios for future global warming and up to a 1% annual increase in nighttime light intensity. We found that increasing nighttime light would likely continue to shift the start of the season earlier, though its influence on the fall color change timing was more complex.

Why it matters

This kind of shift in plants’ biological clocks has important implications for the economic, climate, health and ecological services that urban plants provide.

On the positive side, longer growing seasons could allow urban farms to be active over longer periods of time. Plants could also provide shade to cool neighborhoods earlier in spring and later in fall as global temperatures rise.

But changes to the growing season could also increase plants’ vulnerability to spring frost damage. And it can create a mismatch with the timing of other organisms, such as pollinators, that some urban plants rely on.

Charts show the intensity of urban light in seven representative cities
Urban light intensity varies among cities, and among neighborhoods within cities. Yuyu Zhou, CC BY-ND

A longer active season for urban plants also suggests an earlier and longer pollen season, which can exacerbate asthma and other breathing problems. A study in Maryland found a 17% increase in hospitalizations for asthma in years when plants bloomed very early.

What still isn’t known

How the fall color timing will change going forward as night lighting increases and temperatures rise is less clear. Temperature and artificial light together influence the fall color in a complex way, and our projections suggested that the delay of coloring date due to climate warming might stop midcentury and possibly reverse because of artificial light. This will require more research.

How urban artificial light will change in the future also remains to be seen.

One study found that urban light at night had increased by about 1.8% per year worldwide from 2012-2016. However, many cities and states are trying to reduce light pollution, including requiring shields to control where the light goes and shifting to LED street lights, which use less energy and have less of an effect on plants than traditional streetlights with longer wavelengths.

Cars are parked on an old brick residential street at dusk with street lights and trees lining the sidewalks.
Baltimore has been converting its streetlights to LED to save money on energy. LEDs also have less of an impact on plants. Cyndi Monaghan via Getty Images

Urban plants’ phenology may also be influenced by other factors, such as carbon dioxide and soil moisture. Additionally, the faster increase of temperature at night compared to the daytime could lead to different day-night temperature patterns, which might affect plant phenology in complex ways.

Understanding these interactions between plants and artificial light and temperature will help scientists predict changes in plant processes under a changing climate. Cities are already serving as natural laboratories.

Yuyu Zhou, Associate Professor of Environmental Science, Iowa State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Light pollution can disorient monarch butterflies

Read the full story from the University of Cincinnati.

Biologists say nighttime light pollution can interfere with the remarkable navigational abilities of monarchs, which travel as far as Canada to Mexico and back during their multi-generational migration. Researchers found that butterflies roosting at night near artificial illumination such as a porch or streetlight can become disoriented the next day because the light interferes with their circadian rhythms. Artificial light can impede the molecular processes responsible for the butterfly’s remarkable navigational ability and trigger the butterfly to take wing when it should be resting.

Bird law spells lights out for city-owned buildings in bid to save feathered friends

Read the full story at The City.

Legislation recently passed by the [New York City] City Council will force city-owned buildings to turn off the lights at night — saving electricity and eliminating some of the visual pollution that both draws and confuses birds navigating the big city.

Coupled with a law that came into effect in January requiring new buildings to incorporate bird-friendly designs — including simple window decals to warn them away from glass towers — avian advocates hope the Council moves will make a difference in the wake of climate-related threats to our feathered friends.

LED streetlights decimating moth numbers in England

Read the full story in The Guardian.

‘Eco-friendly’ lights found to be worse than sodium ones – but both contribute to insect decline, says study.

Ideas inspired by nature could change the way our towns and cities look

Read the full story from CNBC.

Daan Roosegaarde is an artist based in the Netherlands. Alongside a team of engineers and designers, his “social design lab” produces work that attempts to boost quality of life in urban settings.

The Dark Side of Light

Read the full story in The Atlantic.

Beneath the surface of one of Germany’s deepest lakes, researchers are studying the hidden effects of artificial light.

Where the last pristine skies in America are

Read the full story in the Washington Post.

There are precious few places left in the United States where you can still view a “pristine” night sky, according to a new study in the Journal of Environmental Management. Situated far from the glare of city and small town lights, these places offer the same unimpeded view of the cosmos that our ancestors saw thousands of years ago, before electric lighting conquered the darkness.

The study, led by Fabio Falchi of the Light Pollution Science and Technology Institute in Italy, plotted artificial light pollution at the county level in the United States, research that builds on a global atlas that he and others produced in 2016. It also adds to a growing body of research on light pollution, which has been linked to a host of ailments — such as depression, obesity, even cancer — and can confuse wildlife, muddling their sense of direction and migration patterns.

Light pollution may be increasing West Nile virus spillover from wild birds

Read the full story from the University of South Florida.

House sparrows infected with West Nile virus (WNV) that live in light polluted conditions remain infectious for two days longer than those who do not, increasing the potential for a WNV outbreak by about 41%.

Nighttime pollination under threat from light pollution

Read the full story from Mother Nature Network.

Writing in the journal Nature, a group of scientists from Switzerland has identified light pollution as a previously unknown threat to nocturnal insects (beetles, moths and flies) vital in the pollination of crops and wild plants. To study its impact on nighttime communities, the team deployed standard LED street lights over plots of cabbage thistle in the remote meadows of the Bernese Prealps.