The Fallout From Chernobyl

In the wake of the accident, the Soviet government established an “exclusion zone” around the damaged nuclear station where human access is restricted. It currently spans about 4,100 square kilometers (1,600 square miles)—an area larger than Rhode Island (see “The Exclusion Zone”). Tim Mousseau, an evolutionary biologist at the University of South Carolina, first visited the zone in 1999. At the time, Mousseau says, the most heavily contaminated areas looked “like a lunar landscape, a gray wasteland. Other parts were less affected. It was so dismal, I didn’t think I’d ever go back.”

But Mousseau realized Chernobyl was a unique place to study how environmental stress affects natural populations. For 25 years, he and collaborators have entered the disaster zone for weeks at a time to examine the impact of radiation on animals and plants there.

After the accident, the Soviet government established an “exclusion zone” around the damaged nuclear station. Human access is restricted there. Today the zone covers about 4,100 square kilometers (1,600 square miles). That’s larger than Rhode Island (see “The Exclusion Zone”). Tim Mousseau first visited the zone in 1999. He’s an evolutionary biologist at the University of South Carolina. Back then, the most heavily contaminated areas looked “like a lunar landscape, a gray wasteland,” says Mousseau. “Other parts were less affected. It was so dismal, I didn’t think I’d ever go back.”

But Mousseau realized Chernobyl was a unique place. Scientists could study how environmental stress affects natural populations there. For 25 years, he and co-workers have entered the disaster zone for weeks at a time. They’ve studied the impact of radiation on the animals and plants.

The effects of radiation exposure differ across species. Radiation can damage an organism’s DNA—the molecule that carries hereditary information—leading to cancer, birth defects, and other health issues (see “Radiation’s Effects”). The scientists have documented increased rates of tumors (abnormal growths), eye problems, and smaller brains in birds in more contaminated areas. They’ve also found reduced numbers of insects and spiders in highly radioactive spots. “Smaller organisms that tend to stay in smaller territories appear more likely to show effects from radiation,” says Mousseau—perhaps because they may spend their whole lives in one highly contaminated place. The researchers have also found problems with reproduction among plants exposed to high radiation: Their pollen is less likely to pollinate flowers, and seeds are less likely to sprout.

Some organisms are coping better than others. For example, data hints that certain birds may adjust their body chemistry to better handle radiation exposure. “That’s a big interest for us—what makes one species more vulnerable while another seems resilient,” says Mousseau. There’s also variation across the zone. “The radiation is very patchy,” says Mousseau. “There are vast areas that are not heavily contaminated. Many animals there are doing quite well—some might even say thriving.”

The effects of radiation exposure differ across species. Radiation can damage an organism’s DNA. This molecule carries hereditary information. The result can be cancer, birth defects, and other health issues (see “Radiation’s Effects”). In more contaminated areas, the scientists found increased rates of eye problems and tumors, or abnormal growths, in birds. Birds in these places also had smaller brains. And they saw fewer insects and spiders in highly radioactive spots. “Smaller organisms that tend to stay in smaller territories appear more likely to show effects from radiation,” says Mousseau. Maybe that’s because they spend their whole lives in one highly contaminated place. The researchers also studied plants exposed to high radiation. They found problems with reproduction. The plants’ pollen is less likely to pollinate flowers, and seeds are less likely to sprout.

Some organisms are doing better than others. For example, data hints that certain birds may adjust their body chemistry. Then they can handle radiation exposure better. “That’s a big interest for us—what makes one species more vulnerable while another seems resilient,” says Mousseau. And there are differences across the zone. “The radiation is very patchy,” says Mousseau. “There are vast areas that are not heavily contaminated. Many animals there are doing quite well—some might even say thriving.”

Wildlife ecologist Jim Beasley of the University of Georgia glimpsed this more hopeful side of Chernobyl on his first trip to the area in 2012. Entering the zone, he says, “you’re acutely aware of the tragedy of this place. You see abandoned homes and toys. Yet it’s also a beautiful landscape, and there’s so much wildlife. Driving around, you see large mammals, like in a national park. I didn’t anticipate that abundance and diversity.” The presence of wolves especially stood out to Beasley. These predators need a steady supply of prey to survive, which meant there must be plenty of animals around for them to eat.

Beasley collaborated with an international team to study changes in populations of large mammals in the zone. They analyzed data from helicopter surveys, studies of animal tracks in snow, and camera traps that snap photos of passing wildlife. Their results suggested that in the decade following the accident—with no people around—large mammals like moose, deer, and wild boar increased in numbers. “Larger animals typically need a lot of space,” says Beasley.  “Additionally, species like wolves and boar may be hunted by people. Those are some of the populations that we see doing particularly well” in the absence of humans, he says.

Jim Beasley saw this more hopeful side of Chernobyl on his first trip there in 2012. He’s a wildlife ecologist at the University of Georgia. When you enter the zone, “you’re acutely aware of the tragedy of this place,” he says. “You see abandoned homes and toys. Yet it’s also a beautiful landscape, and there’s so much wildlife. Driving around, you see large mammals, like in a national park. I didn’t anticipate that abundance and diversity.” Beasley especially noticed the presence of wolves. These predators need a steady supply of prey to eat. That meant plenty of animals must be around. 

Beasley studied changes in populations of large mammals in the zone. He worked with an international team. They examined data from helicopter surveys, studies of animal tracks in snow, and camera traps. These cameras snap photos of passing wildlife. Their results suggested that, with no people around, large mammals increased in numbers in the decade after the accident. These animals included moose, deer, and wild boar. “Larger animals typically need a lot of space,” says Beasley. “Additionally, species like wolves and boar may be hunted by people. Those are some of the populations that we see doing particularly well” without humans present, he says.