Beijing's Polluted Skies Help Trees Grow Better?
Forget what you know, ye survivors of the Airpocalyse!
Though you may have learned to eke out your existence within
hermetically-sealed homes and come to associate the phrase "carry
protection at all times" with air filters, know that the same air
pollution against which you frantically try to protect yourself
apparently also serve to make Beijing's trees grow better and stronger.
A government-backed study conducted by the Chinese Academy of Sciences (CAS) followed
the progress of six Beijing aspen trees between 2012 and 2015 only to
discover that the trees tended to grow best during times of thick smog,
reported the South China Morning Post (SCMP).
Scientists
discovered that aerosols present in the grey haze lingering over
Beijing actually help plants photosynthesize, the process by which light
is converted into energy. Additionally, the aerosols encourage plants
to open their pores (called "stomata") that further aid photosynthesis
as well as respiration.
Tree enthusiasts may feel emboldened at
this news, but the benefits of city life don't stop there for our wooden
friends. German scientists said in a study released last year that the
heat island effect produced by cities help local trees grow faster.
Seeing
as that makes two harmful urban by-products that benefit trees, we're
tempted to give up and switch places with our arbor-inclined friends.
And yet, in keeping with the mind-bending news that the bad things of a
city turn out to be good for trees, we've found that, despite an ongoing
campaign to plant millions of trees around the city and the country at
large, it turns out that trees can be bad for a city because they encourage air pollution.
If
you truly have forgotten what you know, you're ready for this
mind-bender: the presence of too many trees in an urban area can
increase local levels of air pollution by not allowing smog to
dissipate. Streets lined with trees may inadvertently create a "green
canopy" that traps polluted air close to the ground, thereby mitigating
the ability of the trees to remove pollution from the air. The finding
has been so influential that cities are being urged to plant low-lying
hedges instead of their nest-carrying cousins.
But the punitive effects of trees don't stop there. No, not when it's shown they are outright killers.
Often
touted for their smog-busting ability, some trees in fact produce air
pollution in the form of biogenic volatile organic compounds that react
in the air to form ozone and secondary organic aerosols.
Sure,
this naturally-occurring phenomenon wouldn't be much of a concern for
the rest of the world. However, in Beijing, the six tree species
exclusively planted across the city are high emitters of this compound.
Tsinghua University associate professor Jun Yang at
the Center for Earth System Science said there's no definite proof of
trouble so far, but that it may be "problematic" in the future.
Be
that as it may, a decades-long effort has already resulted in millions
of trees of the same species growing throughout Beijing, resulting in
the city's annual "spring snowfall" phenomenon that brings seasonal allergies and fires among other problems.
READ: Allergies Begone! Beijing Promises to Fix its Out-of-Control Catkins Problem by 2020
As
much as we can't change the past, it appears that for whatever we've
come to know about trees and their effect upon the city, we are still
going to get even more of them. As seen in the latest CAS study that
found smog to be beneficial to trees, the main takeaway was that their
findings will likely lead to even more trees being planted in the
capital.
"This is because trees that absorb major greenhouse gas
carbon dioxide will grow slower than they did once the aerosol
concentration decreases," explained Institute of Botany head researcher Liu Lingli, who added that more trees will be needed to absorb greenhouse gasses, one of their primary functions.
With
all that's said and done, it's more than clear that trees are taking
advantage of our invitation to stage a coup of our fair city. And as
shocking as these revelations have been, it shouldn't be that surprising
considering that the trees are committing treason.
Images: Minube.hk, drben.net, amanaimages.com, bookiraj.com
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