Today's episode is sponsored by Brilliant.

Go to Brilliant.org/SciShow to learn how you can take your STEM skills to the next level. [♩INTRO]. Across the US, cities and counties have been working hard to transform the areas around roads into healthy habitats for important pollinating insects, since their populations are declining.

And research has found that helpful bugs do love our roadside landscapes! Which is great. The not-so-good news is that these roadside pollinator habitats might also be luring them to their splattery deaths.

There are a lot of roads in this world. Like, roughly 6.7 million kilometers of them in the US alone. That's enough roadway to travel to the Moon and back about 8.8 times!

And, more importantly for insects everywhere, many of these roadways have traffic medians and verges. A traffic median is a physical barrier that separates lanes of traffic. These are often filled with plants that insects really love.

Meanwhile, a verge is the strip of land on either side of a road that's usually made up of bushes, grass, or other types of vegetation. Both medians and verges can be made into ideal living spaces for insects. In fact, the US government passed legislation in 2015 encouraging the creation of pollinator habitats along roadways.

And the positive impacts of planted roadsides on insect biodiversity can be significant. For instance, one study found that there were more species of butterflies living in roadway-adjacent spaces than in similar grassy areas farther away from roads. And another study found that bees were twice as abundant on roadsides planted with native plants versus those planted with non-native ones.

Plus, there were more bee species! So, planting insect-friendly vegetation along roads can attract all kinds of pollinators and support their diversity. And since pollinators are declining globally, it might be easy to think of medians and verges as an ecological oasis for our insect friends.

But… just because planted roadsides can be good habitats doesn't mean their impacts are totally positive. It turns out that they can also be death traps. In 2012 and 2013, a group of scientists decided to figure out just how many bugs end up as roadkill.

They picked a two-kilometer stretch of the Trans-Canada highway in Ontario, then counted the number and species of dead insects they found on the roadway for eight months. The scientists collected about 117 thousand dead insects, and a whopping 96 percent of them were pollinators like butterflies, bees, moths, flies, and wasps. By mathematically extrapolating these results, the researchers predicted that billions of pollinators across North America might be killed by cars each year!

And, keep in mind, that doesn't include any bugs that stuck to the windshield when they were hit or were flung far from the roadway by the impact. So the real numbers are likely higher. According to researchers, these numbers may indicate that vehicular bugslaughter is contributing to pollinator declines.

Which would be the exact opposite of what we're going for by planting along roads. But the Canadian study only focused on one stretch of highway. So, researchers at the University of Delaware decided to study 30 highways in Delaware, Maryland, and Pennsylvania to create an even bigger picture.

They were especially interested in whether the type of vegetation in medians and verges make insect mortality numbers better… or worse. They looked at “lawns”, which were a mix of non-native grasses; “meadows”, which featured wildflowers and tall grasses; and “wooded areas”, which were predominantly trees and shrubs. And…it turned out the presence of a median increased insect deaths no matter what plants were planted in them!

However, they did find that different vegetation types affected species differently. More bees were killed in lawn areas, for instance, whereas butterflies and dragonflies had higher mortality rates when medians featured meadows. Still, findings like these might make planted roadsides seem like a bad idea altogether.

But researchers don't think we should just give up on trying to make them into pollinator habitats. They have some good ideas for how we can continue to use medians and verges to support insect diversity without luring insects to their deaths. For instance, scientists think it'd help to plant insect-friendly vegetation farther

away from roads, as that may convince bugs to stay in their lane, so to speak.

Scientists have also floated the idea of ecological pickiness. That is, instead of planting native plants along all roadways, we could analyze traffic volume and traffic speed to figure out the best roads for planting basically, the ones that are safest for our pollinator friends. One last idea is to develop bug-friendly barriers that help keep insects away from our vehicles.

There's actually been some research into this solution, too. One 2013 study tried using tall screens to prevent ground-nesting bees from crossing a road at car height… but the bees just flew over them and then went back down into the danger zone. A similar 2015 study tried using nets to prevent dragonflies from crossing roadways, with a bit more success.

The nets did seem to work, but given the quote “roads” in that study were simulated in meadows away from traffic, it's unclear whether this method would be effective on real roads. Still, it's encouraging to see this kind of research being done. Because while adding insect-friendly landscaping along roadways can be a good thing, we still don't quite know how to keep our six-legged friends in their habitat and off your windshield.

The kind of innovative problem solving being used to save bugs is important in all kinds of fields. And you can become better at it with a little help from today's sponsor, Brilliant. You see, Brilliant has over 60 interactive courses in math, science, and computer science that use hands-on approaches to teach.

STEM concepts and skills. You can flex your problem-solving muscles in their Logic course, for instance. And as you solve their riddles and puzzles, you'll be training your brain to make accurate, scientific deductions!

You get total access to it and all their other courses with a premium subscription. And if you're one of the first 200 people to sign up for an annual premium subscription at Brilliant.org/SciShow, you'll get 20% off! Plus, you'll also be supporting SciShow—so thank you for that! [♩OUTRO].