Short Wave - Wolves Are Thriving In The Radioactive Chernobyl Exclusion Zone

Episode Date: February 5, 2024

In 1986 the Chernobyl nuclear power plant exploded, releasing radioactive material into northern Ukraine and Belarus. It was the most serious nuclear accident in history. Over one hundred thousand people were evacuated from the surrounding area. But local gray wolves never left — and their population has grown over the years. It's seven times denser than populations in protected lands elsewhere in Belarus. This fact has led scientists to wonder whether the wolves are genetically either resistant or resilient to cancer — or if the wolves are simply thriving because humans aren't interfering with them. This episode, researchers Shane Campbell-Staton and Cara Love talk through what might be causing this population boom. Plus, why researchers in the field of human cancer are eager to collaborate with them.Want to hear about other ways humans are impacting the planet? Email us at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. If you go to Pripyat or other small towns in northern Ukraine in Belarus, you'll find them empty. They're ghost towns, and they have been since 1986 when a reactor exploded at the Chernobyl nuclear power plant. It released over 100,000 pounds of radioactive material into the atmosphere, and that dispersed really all across Europe and the USSR at the time. That's Kara Love. She's a biologist and postdoctoral fellow at Princeton University. She told me the most heavily contaminated area is right around the reactor. That whole region was evacuated by all the human inhabitants. Over 100,000 people from over 200 different villages.

And that's what we referenced to as the CEEZ. Or the Chernobyl exclusion zone. Kara's been to the Belarus portion of the exclusion zone for research. When she went, she had aware D'Aseimilar. to monitor the radiation exposure and to make sure she didn't go anywhere too radioactive. So I'm mostly in smaller abandoned towns. Villages that still have cars in the driveways or they still have books on the bookshelves within the homes. There are still shoes near the front doors.

When people were evacuated, a lot of them were told they could come back. Most of their belongings are untouched. But now? The vines are crawling through the windows. Some have trees from the floor that are growing up through the roof in the center of the house at this point. But perhaps some of the most remarkable or memorable interactions of the homes and the wildlife is that you sometimes see a boar's nest or where a boar has spent the night with its babies. Within the CEEZ, evolutionary biologist Shane Campbell-Staten says there's an entire functional ecosystem.

Everything from amphibians, insects, and birds to megafauna, so things like European bison, boar, apex predators like wolves. So Shane mentions wolves. The wolves are particularly interesting here. As the apex predators, wolves would theoretically be hit hardest by the Chernobyl radiation. They're eating the radioactive deer that's eating the radioactive plants. And all that radiation exposure builds as you climb up the food chain. Gray wolves offer a really interesting opportunity to understand the impacts of chronic, low-dose, multi-generational exposure to ionizing radiation because of the role that they play in their ecosystems.

Kara is a postdoc in Shane's lab, and she approached Shane with this wolf problem because of one shocking fact. So wolves within the Chernobyl exclusion zone have been estimated. to actually be about seven times as dense as populations in other protected areas within Belarus. The wolves are thriving and no one knows why. Today on the show, the mystery of how gray wolves survived decades of radiation and took back Chernobyl. I'm Regina Barber, and you're listening to Shorewave, the science podcast from NPR. When Kara approached Shane about these gray wolves in the Chernobyl exclusion zone,

she just wanted to know the basics. How much radiation are individuals exposed to? Are these levels significantly higher than regions outside of the exclusion zone, which we found that they are extremely significantly higher? But from there, they had a bigger question in mind. As an evolutionary biologist, the very first question in my mind was whether or not this radiation was enough of a stressor to actually be, a selective pressure. Was the radiation from Chernobyl driving natural selection

and triggering the gray wolf population to evolve in ways that would protect it from radiation? There may be genetic variation within the population that may allow some individuals to be more resistant or resilient in the face of that radiation, in which case they may still get cancer at the same. rate, but it may not impact their function as much as it would, you know, an individual outside of the exclusion zone. They're just able to take that burden better for some reason.

Or it could be resistance, right? And despite that pressure, that radiation exposure, they just don't get cancer as much. Shane and Kara hypothesized that over the past few decades, the gray wolves with the genes that allowed them to withstand the radiation, have been able to survive where the others have died off. And those are the wolves procreating and passing on those genes. Basically, the population is rapidly evolving. But to know for sure, they had to get into the Chernobyl exclusion zone.

Nowadays, the zone is a lot safer with proper protective equipment. Some people have even moved back to live there. A lot of the people that were evacuated had a really strong stigma attached to them, and many of them just wanted to go home. You know, they wanted to go to the land that their family had been on for quite some time. In the small villages around Belarus, Karen, her team, had developed a wolf collar that had a decimeter built into it to measure how much radiation the wolves are exposed to. They also do genetic blood testing on the wolves.

So we're looking at blood cell composition because there's lots of different immune blood cells that circulate within our body, and they can be indicative of different types of stress. or disease. So by counting the number of different immune cells within an individual, we're able to identify some signature of radiation stress within the Chernobyl wolves. And we've also explored many different parasite and pathogen infections within this population compared to reference populations trying to get at disease rates. For reference populations, Karen Shane looked at two other sets of gray wolves. One in another protected area of Belarus outside of this easy and one much further away in Yellowstone National Park.

Really what we were interested in is trying to identify regions of the genome that seem to be diverging much faster in Chernobyl than they are elsewhere. So if you have a population that is exposed to a particular pressure, comparing it to several other populations that aren't exposed to that pressure gives you an idea of where that selection might be happening in the genome, which genes may be changing in response to that selection. In other words, Shane and Kara are hoping to identify the genes that have allowed these gray wolves to withstand the radiation and all of its bad health effects. So what did you find then? What were the small differences if there were any? So in general, we found that the fastest evolving regions within Chernobyl are in and around genes that we know have some role in cancer immune response or the anti-tumor immune response in mammals.

Cancer is one of the biggest health impacts of the radiation from Chernobyl. In the area after the accident, there were at least 1800 documented. cases of thyroid cancer in kids under 15. That's a lot higher than normal. And Kara says that extends to other life in the C.E.Z. Dogs within Chernobyl have higher cancer rates than dog outside of Chernobyl. And if we extrapolate that into the wolf population, we can assume that they might have higher cancer rates.

But they've also possibly show higher resilience within these genes that we find that are under selection. So the detrimental impacts of that cancer, even if it does exist within the population, may not be as strong. The major question that we had was, is there selection happening? Our data clearly show that there is a genetic component and a significant and strong genetic component. That does not mean that the entire story is based around genetics. This might be why the wolf population is thriving. After generations of developing a resilience or resistance to cancer,

they're now successful apex predators in an area once devoid of much other life. But Shane says even if natural selection is at play here, there's another big factor at play. The other thing is humans aren't there, right? A wolf within the Chernobyl exclusion zone, it may have to deal with pressures from Canada. but it doesn't have to deal with pressures from, say, hunting. And it may be that the release from that hunting pressure, that separation from humans, turns out to be a much better thing than having to deal with cancer, which is kind of messed up. So when you think about that initial conundrum,

why is the wolf population in Chernobyl estimated to be seven times denser than in other areas? It's hard to know exactly why. Maybe wolves with cancer-resistant or resilient genes are naturally selected. Maybe they just don't need to worry about humans. Karen and Shane say it's probably a bit of both. But they hope to take more trips to the CEEZ to figure this out. And they also think that if they're able to identify the genes responsible for this cancer resilience or resistance in wolves, it could inform human cancer treatments. We have started collaborating with cancer biologists and cancer companies.

to help us to interpret these data and try to figure out if there are any directly translatable differences that may offer like novel therapeutic targets for cancer in humans, for instance. Since the war in Ukraine started nearly two years ago, Shane and Kara have put a pause on their research. And unfortunately right now, you know, with the war and everything going on in the region, we aren't able to get back out to be able to ask directly, what's happening in the region now is obviously far more important than research at the moment. So priorities are where they should be, I think.

So I think we're used to evolution being slow, right? Like a gradual process. But is that still true? That is, I think, one of the major things that has, I think, fundamentally shifted in the Anthropocene, in the age of humans. It's like, we don't do anything just a little bit. Right. Anytime we impact the environment, we do it in a big way, which creates very strong selection pressures. Unfortunately, that strength of selection, like the more a population changes due to selection, the greater a toll it takes.

Because evolutionary response to selection comes at a cost, and that cost is death. The stronger the response is, the more individuals that had to die. in order to get that response. Both Shane and Kara have been thinking about this a lot. Shane's lab studies how human activity has triggered evolutionary change. These gray wolves are only one example of that. There are going to be a lot of changes that happen in a very short period of time. And the pace and magnitude of that change, you know, if we look back through the history of life on this planet,

I mean, it can only be equivalent. to the five major mass extinction events that the planet has experienced in the past. So to think of us as a destructive force, you know, equivalent to, you know, the asteroid that killed off the dinosaurs, you know, it sort of puts in perspective both the power of what it means to be human, but also, you know, the sort of responsibility to, wield that power in a way that isn't destructive. The CEZ has transformed rapidly over the last few decades. Think about a place like Pripyat.

Almost four years ago, it was this small city of about 50,000. Then it became a radioactive ghost town. And now, it's somewhere in between. It's a home base for boars and wolves, and some people who have managed to find their way back. All of its residents are at the wind of a rapidly changing world. Just trying to keep up.

This episode was produced by Margaret Serino and edited by a showrunner, Rebecca Ramirez. It was fact-checked by Britt Hansen. Josh Newell was the audio engineer. I'm Regina Barber. Thank you for listening to Shortwave from NPR.