Study Draws Southern California Coastal Light Pollution into Focus
Arthur T Knackerbracket has found the following story:
The Santa Monica Pier at night. Artificial light can cause problems for a range of species that live and breed in coastal environments.
When tides are at their highest a few days after a full or new moon, thousands of small silver fish called grunion flop onto Southern California beaches. Females wriggle their tails into the sand, males spray the females with sperm, and the fertilized eggs are deposited below the beach surface. The entire affair lasts no more than a minute or two.
Ten days later, the eggs hatch and baby grunions are washed out to sea.
Artificial light is known to disrupt mating cycles in species like the grunion - as well as disorient insects and upset predator-prey relationships - along the Southern California coast. With those harmful effects of artificial light in mind, a team of UCLA and University of Southern California researchers led by Travis Longcore, UCLA adjunct professor of urban conservation biology, have mapped light pollution conditions at hundreds of locations along the coast that they will use to inform decision-making for future infrastructure and construction plans.
A database of their findings is described in a new paper in the journal Environmental Research Communications. Because the database combines ground-level measurements with satellite data, it is one of the world's most accurate databases of light pollution.
[...]The challenge for researchers is that satellite imagery - the technology that has traditionally been used to study light intensity at ground level - hasn't been thought to be totally accurate or precise. For one thing, a single pixel on a satellite image can cover a large area on the ground - upwards of 700 square meters (about 7,500 square feet). And clouds can cause light to scatter and as[sic] it travels from earth to space, which can distort the satellite readings.
To check the accuracy of satellite measurements, Longcore and his colleagues developed a technique to measure artificial light on the Southern California coast. Using specially designed software that quantifies the amount of light in each picture, the researchers took photos of the night sky at 515 locations along the coast. They used a specialized hemispheric camera lens - similar to a fisheye lens - to capture the entirety of the sky in each photo. Then the team compared their on-the-ground measurements of light at night with satellite data.
They were surprised to find that many of the satellite measurements, despite being imprecise because of poor image resolution, were accurate.
[...]Aside from grunion, artificial light causes problems for an array of other species: It distracts moths from pollinating plants; tricks newly hatched sea turtles into heading inland, rather than to the ocean; and makes it difficult for snowy plovers, a threatened species, to find beaches that are dark enough to safely lay their eggs.
[...]Longcore's next project will use the light pollution database to help the California Department of Transportation assess the possible effects of installing more energy-efficient highway lighting on Southern California wildlife.
Journal Reference:
Ariel Levi Simons, Xiaozhe Yin, and Travis Longcore. High correlation but high scale-dependent variance between satellite measured night lights and terrestrial exposure - IOPscience, Environmental Research Communications (DOI: )
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