The bright lights of the big city cause flowers to bloom prematurely, a new study shows.
An academic has found that trees in American cities are sprouting earlier than in rural areas, probably due to artificial light from street lamps, billboards and more.
Artificial light significantly alters the normal day-night cycle that plants rely on, but is often overlooked when authorities develop lighting strategies for city streets.
Trees that bud too early may “mismatch” the timing of other organisms, such as pollinators, which can jeopardize their survival.
Pictured are artificial light sources after dark in Beijing, China, including street lamps and light from inside buildings. Artificial light is often overlooked when authorities develop lighting strategies for city streets, even if it can lead to earlier blossoms
STREET LAMPS ‘KILL OFF INSECTS’
Environmentally friendly light-emitting diode (LED) lights used in street lamps produce more light pollution and kill insects, a study shows.
Researchers found that LED streetlights kill nighttime moth caterpillar populations by 50 percent, compared to areas without the lights.
Despite being considered environmentally friendly, LED bulbs are even more harmful to insect populations than the traditional yellow sodium bulbs.
Read more: LED street lights kill insect populations by half, study finds
The study was conducted by Lin Meng, a postdoctoral researcher at the Lawrence Berkeley National Lab in Berkeley, California, who described her findings in the journal Science.
“Trees don’t have watches or calendars, but they seem to know better when spring comes than we do,” she said.
“The timing of seasonal biological events – such as when trees sprout, flowers open and leaves turn yellow – is called phenology.
‘With satellites we can observe when plants all over the world turn green in spring.’
Using satellite data, Meng compared spring “greening dates” in urban and rural areas in the 85 largest U.S. cities for the period 2001-2014.
She found that spring occurred on average six days earlier in urban areas than in rural areas, largely due to warmer city temperatures.
“The six-day difference was mainly caused by warmer city temperatures, which averaged 1.3°C” [2.3°F] higher than the surrounding rural temperatures,” Meng said.
Her analysis also found that while urban tree greening shifted significantly earlier than rural tree greening under climate change, urban tree greening responded more slowly to climate change than rural trees.
The timing of ‘spring greener’ has changed in US cities compared to rural areas, due to artificial lighting, new study finds
“Urban trees were not cooled enough in the winter and therefore responded less well to rising temperatures in the spring,” says Meng.
“In contrast, urban trees in some warm southwestern or coastal regions (Texas, Louisiana, and Florida, for example) responded better to temperature than their rural counterparts, perhaps as a strategy to cope with drier conditions.”
A warming climate is already known to have shifted the timing of global seasonal tree events such as leaf budding and greening – also known as phenology.
But urban environments pose additional challenges for trees, in the form of artificial light.
These additional changes “have cascading effects on the ecosystem” and could affect phenology even more than climate warming.
Tree leaves are budding earlier in American cities compared to rural areas, and that artificial light could accelerate this effect as the climate warms. Pictured, cherry blossom in Beijing
URBAN HEAT ISLANDS
Urban heat islands occur when cities replace natural land cover with dense concentrations of pavement, buildings and other surfaces that absorb and retain heat.
This effect increases energy costs (e.g. for air conditioning), air pollution and heat-related illness and death.
As a result, these locations can be up to 5.4°F (3°C) warmer than rural areas – a phenomenon known as the ‘urban heat island effect’.
‘We as ecologists know a lot about the impact of warming and increased carbon dioxide concentration on plants, because these are the two most important aspects of climate change,’ says Meng.
“But light doesn’t change in nature, so most people just haven’t thought of it.”
Meng’s interest in this area was sparked by a trip to see cherry blossoms in Beijing, China, in 2015.
“The forecast showed that the bloom time was 10 days early in downtown Central Park,” she said.
“The night before I had planned to visit Central Park to see the blossoms, but the snow came unexpectedly, and what I saw the next day was an almost complete loss of those emerging blossoms.”
In future research, Meng wants to investigate how different vegetation types respond to different parts of the light spectrum.
For example, LEDs that emit broad spectrum light will have a different ecological impact than sodium street lamps that mainly emit in the yellow-orange part of the spectrum.
Another area of focus is identifying the critical period when trees are most sensitive to artificial light.
“Answers to these questions will inform decision-making about what types of light we need for different locations to minimize ecological impacts,” Meng said.
LIGHT POLLUTION IS ARTIFICIAL LIGHT THAT IS EXCESSIVE, MEMORABLE AND WASTE
Light pollution, also called photo pollution, is the presence of anthropogenic light in the nighttime environment.
Artificial light that is excessive, intrusive and ultimately wasteful is called light pollution and directly affects how clear our night sky appears.
With over nine million street lamps and 27 million offices, factories, warehouses and homes in the UK, the amount of light we throw into the sky is staggering.
As some light escapes into space, the rest is scattered by molecules in the atmosphere, making it difficult to see the stars against the night sky. What you see instead is ‘Skyglow’.
The increasing number of people living on Earth and the attendant increase in inappropriate and unshielded outdoor lighting has led to light pollution – a brighter night sky that has obliterated the stars for much of the world’s population.
Most people have to travel far from home, away from the glow of artificial light, to experience the awe-inspiring expanse of the Milky Way as our ancestors once knew it.
Light pollution is excessive and inappropriate artificial light. As some light escapes into space, the rest is scattered by molecules in the atmosphere, making it difficult to see the stars against the night sky. What you see instead is ‘Skyglow’
The negative effects of losing this inspiring natural resource may seem elusive.
But a growing body of evidence links the clearing night sky directly to measurable negative effects on human health and the immune system, to adverse behavioral changes in insect and animal populations, and to a decline in both the environmental quality and safety of our nighttime environments.
Astronomers were among the first to document the negative effects of wasted lighting on scientific research, but for all of us, the negative economic and environmental effects of wasted energy are evident in everything from the monthly electricity bill to global warming.