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If you are from the parts of Asia where this plant is indigenous,
or the southeastern US where it definitely is not,
you already know what you’re looking at.
For the rest of you: meet kudzu, a plant so aggressively invasive in the US that it’s
known to take over utility poles, abandoned buildings,
and cars that don’t move out of the way fast enough.
That is not me exaggerating for humorous effect. It is a thing that happens.
But even though this vine has basically taken over the entire Southeast,
it’s even worse than you think.
Because according to researchers, it’s kind of poisoning the air around it.
Kudzu was deliberately introduced in the Southeast
as an ornamental plant and livestock feed.
And it’s not all bad. Parts of the plant are edible for humans as well as animals,
and historically it’s even been used to make clothing and paper.
Problem is, it got real comfy.
It’s difficult to get a solid estimate for how much is out there,
and the kudzu that’s visible from roadsides all over the South
may make it seem more overwhelming than it is in reality.
But, still, it’s definitely an invasive species of some concern.
And kudzu doesn’t just grow. It can shape the nutrient balance of its environment
in a way relatively few plants can, because kudzu is a bean.
A legume, that is. And legumes have the ability to fix nitrogen,
meaning they take nitrogen gas from the atmosphere and trap it
in a form that’s available as a nutrient.
Now, I just told you we don’t know exactly how much kudzu is out there.
But one estimate goes as high as 3 million hectares in the southeastern United States.
And if you run the numbers, that would mean kudzu has a more significant effect
on the nitrogen cycle than soybeans,
even though those are grown in the South on purpose.
But that doesn’t mean it’s just, like, fertilizing the whole region.
A landmark 2010 study suggested that kudzu is having such a significant effect on
the balance of atmospheric gases that it’s affecting air quality.
Here’s how it works: First, kudzu converts atmospheric nitrogen gas into
ammonium in the soil. Then, soil bacteria convert the ammonium into nitrate,
and further reactions cause nitric oxide and nitrous oxide to escape into the air.
Nitrous oxide is already a greenhouse gas, so we’re off to a bad start.
But that nitric oxide is an even bigger problem, because it’s an important factor
in the creation of ozone.
So, ozone is happy and fine when it’s way up in the stratosphere,
where it helps protect the Earth from harmful radiation.
Down here at the surface where we have to breathe it in, it’s a different story.
Ozone is harmful to the respiratory tract, especially when you have a condition like
asthma to make things worse.
It’s an important source of air pollution, and…it’s a greenhouse gas, too.
Cars and factories tend to spit out nitrogen oxides that lead to ozone formation,
and for that reason, a lot of air quality legislation targets nitrogen emissions.
But those laws won’t stop kudzu, because it can’t read.
The researchers in that 2010 study compared soil plots with and without kudzu
and measured the effect on nitrogen cycling and surrounding air quality.
By scaling up those numbers to apply to the whole Southeast, they estimated that
the number of days where atmospheric ozone is at unsafe levels would go up,
especially in parts of Tennessee, Arkansas, and Mississippi.
In those regions, they predicted up to an extra seven days of high ozone levels.
That’s an extra week where sensitive groups would want to avoid going outside,
in the summertime when conditions are at their worst.
Now, the authors do say this is likely a high-end estimate of kudzu’s impact.
However, they claim their research shows how natural, or not-so-natural,
forces can totally undermine our best attempts at cleaning up the environment.
It’s definitely a reminder that Earth is a complex system.
We’ve caused all kinds of problems by introducing invasive species,
but one that causes air pollution really takes the cake for me.
We have to be careful stewards of this planet
before it gets swallowed by car-eating illiterate vines.
Thanks for watching this episode of SciShow, and if you want to see more videos
about everything from car-eating vines to the shape of black holes,
you can consider supporting the channel on Patreon.
Patrons get access to some fun perks like monthly bloopers,
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