What happens if you’re a person that needs to get from one side of a busy highway to another? You probably go over a bridge or through an underpass. But what do you do if you’re an animal?
Lesson summary
Hi there everyone, I’m Jeff; JR is the producer; and you are listening to Plain English, the best way to upgrade your English with current events and trending topics.
Coming up today: Highways are a fast and convenient way for humans to get from place to place. But for animals, it’s the opposite. Highways don’t help animals get around; actually, they stop animals from getting where they need to go. Engineering created this problem, and engineering has a solution. That’s what we’ll be talking about on today’s lesson.
In the second half of the lesson, we’ll be talking about the phrasal verb “cut through,” and JR has a song of the week. Let’s get started.
Wildlife crossings help animals navigate around highways
U.S. Highway 101 hugs the coast of the Pacific Ocean. It’s one of the most beautiful roadways in all of North America; car companies often film commercials showing their vehicles with stunning natural landscapes in the background. Road trippers make the drive from southern California to Washington State, watching as their surroundings transition from palm trees to mountains to cliffs to forest.
But Highway 101—like many highways around the world—has another legacy. It’s harming the animal species in the area.
Here’s an example. The road cuts through the Santa Monica mountains, which have long been home to mountain lions. The mountain lions that live in the area have no safe way to move about their natural habitat: the highway acts as a wall that prevents them from crossing from one area to another. As a result, a small population of mountain lions on one side of the highway is isolated from the larger population on the other side. This has caused the genetic diversity of the smaller population to fall.
What does that mean? With a smaller population, there are fewer potential mates for each male and female mountain lion. And that means that they more often mate with close relatives. Researchers studying photos and autopsies of mountain lions have identified physical deformities that come from lower genetic diversity. Scientists fear that if nothing is done, the smaller population will die out.
This example illustrates that highways around the world have unexpected impacts on animal species. The obvious impact, though, is collisions. In the U.S. alone , a million animals are killed on the roads each day. One study found that 12 percent of wild mammals in North America die on the roads. And many of those mammals are endangered. A Department of Transportation study identified 21 endangered or threatened species that are at high risk of roadway crashes.
Other species don’t stay in the same place all year round. Elk and deer, for example, migrate. But highways can impede their progress, trapping them in places they wouldn’t naturally be. Other animals naturally move about the world as local conditions change. If a river dries up, if commercial development encroaches on their habitat, or if it’s just getting too crowded, mammals move to more suitable locations—unless, of course, a highway stops them.
There is a potential answer. I opened the lesson by asking, how does a person get from one side of a busy highway to another? The answer is that we take an overpass or underpass. An overpass is a bridge that goes over the road. An underpass is when the main road is the bridge and we go underneath.
So that’s how people can get around major highways. But guess what: it’s possible for animals to do the same thing, if only we build a path that tricks them into thinking it’s not a bridge at all.
The overall concept is called “wildlife crossings.” They can be bridges, underpasses, tunnels, or trenches. But they’re all designed to allow wildlife to safely cross from one side of a highway to another. Back on Highway 101, the state of California is planning the biggest wildlife crossing in America. When complete, it will be 200 feet long and it will cross ten lanes of whizzing traffic.
But this won’t be an ordinary bridge. It will be designed specifically to encourage mountain lions and other critters to use it. That means it will shield noise and light from the traffic below, and it will be specifically landscaped to look like the surrounding area.
It’s a proven concept. A pronghorn is a mammal that looks like a cross between a goat and an elk; they’re native to the western part of North America. For 6,000 years, they have migrated from one part of Wyoming to another, about 170 miles in total. But highways have made that difficult. In recent years, Wyoming has installed bridges specifically designed for pronghorn to cross major highways in the area. Fencing nearby also guides the pronghorn toward the bridges.
Two years after the crossings were built, the state Department of Transportation found a 70 percent reduction in crashes between vehicles and pronghorn on the highways. That shows the pronghorn have adapted to the new crossings—in other words , the animals know what to do. If you’re still not convinced, you can see video evidence from the motion-activated cameras installed to monitor the bridge’s use.
Money has been a major roadblock to constructing wildlife crossings: they cost millions of dollars each. But they also save money because each crash causes property damage and requires public services to clean up the roadway. High speed crashes also cause injuries to drivers.
Studies from Wyoming and Arizona have found that the wildlife crossings pay for themselves in reduced costs after just a few years. The U.S. Congress allocated $350 million from a new infrastructure bill just for wildlife crossings.
But the U.S. is slow to the game; we have only about 1,000 wildlife crossings in our whole vast country. The Netherlands, by comparison, has 600; and they have only 2 percent as much roadway as we do. The Dutch have built the world’s longest wildlife crossing: it’s half a mile long. The idea originated in France in the 1950s and Europe is still the world leader in wildlife crossings.
On Christmas Island in Australia, millions of red crabs migrate from the forests to the beach each year. And they stop traffic to allow the crabs to pass. But they’ve also built simple metal structures that crabs can climb to get up and over the cars passing below.
Good looking bridges
This feels like something we should spend our money on. Set aside the fact that it’s actually cost-effective, since it saves so much money on crashes. We’ve gained so much from our roadway and railway networks, the least we can do is invest a little of that back in limiting the disruption to the natural habitat.
They look good, too, I must say. I saw aerial photos from the Netherlands, Germany, Belgium, Canada, the U.S. And they all look good, they look like the earth has just kind of grown over the highway. I would cross it, if I were an animal. But I wouldn’t go anywhere near that crab bridge in Australia.
Learn English the way it’s really spoken
