Until the 19th century, the Pripyat River basin on the border between Ukraine and Belarus was wetland and forest. As usual, humans kind of ruined it. They burned down forest for pastureland and cut down trees for timber—or for fuel to make glass and vodka. By the middle of the 20th century, most of that industry was gone, and human-driven reforestation efforts had remade the Pripyat region anew. And then, on April 26, 1986, a nuclear power plant called Chernobyl, on the Pripyat River about 70 miles north of Kiev, blew up and caught fire, spewing radiation across the northern hemisphere.

So that was a big change.

The Soviets ended up evacuating 300,000 people from nearly 2,000 square miles around the plant. The bulk of that area is now called the Chernobyl Exclusion Zone, and the old power plant is now encased in a giant concrete sarcophagus. But what happened to the Exclusion Zone after everyone left is the subject of disagreement in the scientific community. For decades, research in the area said that plant and animal life had been denuded, and the life that remained was mutated, sick. Newer research says otherwise—that plants have regrown, and animal life is even more diverse than before the accident. The Exclusion Zone hasn’t been rewilded so much as de-humaned, more unmanned in folly than anything Lady Macbeth ever worried about. It’s a living experiment in what the world will be like after humans are gone, having left utter devastation in our wake.

It’d be easy to assume that exposing 3 billion humans to clouds of radioactive strontium, iodine, cesium, and plutonium would be a Thanos-snappingly bad thing. Some 134 emergency responders around the plant got acute radiation sickness, but 530,000 recovery workers got high enough doses to be worrisome. Studies are ongoing as to what that did to their bodies.

One effect seems uncontroversial: The more radioactive iodine you get exposed to, the more likely you are to have thyroid cancer and other thyroid problems later in life. Clean-up crew members today have disproportionately more instances of leukemia and other cancers, as well as cataracts. Luckily, radioactive I-131 doesn’t stick around. “It has such a short half-life that it disappeared quickly—days and weeks after the accident,” says Jim Beasley, an ecologist at the University of Georgia who studies life in the Exclusion Zone. “The animals in Chernobyl today aren’t exposed to that.”

(The effects of radiation can get weirder. Earlier this decade, a small cluster of elderly New Yorkers were diagnosed with an ultra-rare cancer of the eye and optic nerve—vitreo­retinal lymphoma. Ten of them turned out to have lived near Chernobyl or along the fallout path after the accident.)

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Yes, yes, you are saying, but what about the Exclusion Zone? A mostly conifer forest west of the plant, where radiation levels were the highest, turned red and then died; it’s still called the Red Forest. But elsewhere? Early studies of birds and invertebrates like insects showed population declines, and later work showed the same for large mammals. “If you go to the most contaminated areas, like some sites in the Red Forest, on a spring day, you can barely hear a single bird singing,” says Anders Møller, an ecologist at the University of Paris-Sud who has been studying Chernobyl since 1991. “I’ll bet you that if we went together to the Exclusion Zone, I would be able to tell you the radiation level from the vocal activity of the birds.”

With his frequent collaborator Timothy Mousseau, Møller has long warned of the negative effects of radiation on the ecosystem. The team found, for example, mutation rates two to 10 times greater in barn swallows in the Exclusion Zone than in Italy or elsewhere in Ukraine—and genetic damage in a bunch of other plant and animal species. Signs of radiation damage, like albino patches on birds, are more common near Chernobyl, they say, as are abnormalities in sperm in birds and rodents. (Apparently the longer an animal’s sperm is, typically, the more subject it is to radiation damage. So … watch out, I guess.)