Author: Greg Walters
Posted on: Seeker | 27 th of November 2017


Nighttime on Earth is getting brighter.
The rise of developing economies in Africa, Latin America, and Asia isn’t just raising
global greenhouse gases emissions and making the planet warmer. It’s also spreading
nighttime light to regions of the planet that didn’t have it before, parting the global
curtain of night.

“We’re losing more and more of the night on a planetary scale,” Kip Hodges, professor
of earth and space exploration at Arizona State University and deputy editor of the
journal Science Advances, told Seeker.
The impact won’t just be felt by poets and stargazers.

The dangers, Hodges said, include the “well-established negative effects of light
pollution on human health, ecosystems, and astronomical research.”

According to a new paper published in Science Advances, the artificially lit surface of
Earth at night increased in radiance and extent by about 2 per cent annually from 2012 to
2016. To make that measurement, Hodges and his team used first-ever calibrated satellite
radiometer designed especially for nighttime lights. A radiometer is any device that
measures electromagnetic radiation.

An influx of new light can wreak havoc on natural systems that have evolved to live
partly in darkness, the authors said.

A big example: nocturnal animals, including some 30 percent of vertebrates and 60
percent of invertebrates.

Indeed, changing night patterns threaten biodiversity, migration, and reproduction habits
for a wide range of animals from insects to fish and birds and have an impact on plants
and microorganisms, too.

“From an evolutionary perspective now, artificial light at night is a very new stressor,”
said Franz Holker, one of the paper’s authors. “The problem is that light has been
introduced in places, times and intensities at which it does not naturally occur and many
organisms, there is no chance to adapt.”
To be sure, the increase isn’t uniform around the world.

The authors said the change observed in their study varied greatly by country, with some

places far exceeding the overall global rate.

Some countries, such as war-torn Yemen and Syria, became darker over the course of the
study period.

Some of the world’s brightest nations, like the United States and Spain, remained
relatively stable. But most countries in South America, Africa, and Asia became
increasingly radiant.

Globally, the increase in light emission appears to correspond closely to the rise in
overall economic activity.

For their study, the scientists used a satellite radiometer designed especially for nighttime
lights known as a Visible/Infrared Imager Radiometer Suite, or VIIRS.

Notably, the authors point out, VIIRS only detects light emitted between 500 and 900
nanometer wavelengths. It does not “see” blue light (less than 500 nanometers), which
humans can see, meaning the increases in brightness detected are even greater with
respect to human vision.

“Natural light cycles have been fundamentally disrupted by the introduction of artificial
light into the nighttime environment,” Holker said. “We are convinced that artificial light
is an environmental pollutant with ecological and evolutionary implications for many
organisms from bacteria to mammals, including us humans and may reshape entire social
ecological systems.”
Read at: poses-a- growing-threat- to-human-
health-and- biodiversity