[♪ INTRO] 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, plus the pride of helping the whole  internet learn about monster legumes.

You can get started at patreon.com/scishow. [♪ OUTRO]