Radioactive boars? Nuclear fallout leaves lasting effects on wildlife

September 30, 2023
Science Magazine

Above: Radioactive boar in the wild. Image courtesy of Foreign Policy

The infamous 1986 Chernobyl disaster was much more than the catastrophic meltdown of a nuclear power plant in Ukraine. Apart from causing long-term health effects in humans, this accident impacted entire ecosystems across Europe, as radiation released from the explosion drifted towards the forests of western Europe. Research on feral dogs in the surrounding vicinity found significant levels of unstable cesium isotopes, an indicator of radioactivity, in their bodies. Similar levels of radioactivity have contributed to population reduction, mutations, and genetic breakdown in many species exposed to radioactive disasters. In the years following the Chernobyl accident, researchers reported measurable amounts of radioactivity in species ranging from deer to hare living in the Bavarian forest. Over time, however, the radioactivity in these organisms dwindled in all but one species: the wild boar.

Fungi and Cesium

Wild boars (Sus scrofa) of the Bavarian forests in Southeast Germany contain unsafe levels of radiation to this day. New research has investigated both the persistence and origin of the wild boar’s radioactivity. As of 2020, the Bavarian State Office for Environment and Food Safety found that many boars had levels of cesium far above the safe threshold of 600 becquerels per kilogram (Bq/kg), with some even reaching 10,000 Bq/kg. As a result, hunters take extra precautions to avoid these boars.

Studies have traced one aspect of the boar’s continued radioactivity to their peculiar diet of mushrooms, which are able to absorb more heavy metals than plants. Transported by precipitation, wind, and runoff, radioactive cesium released from anthropogenic sources settles in forests. There, it begins to accumulate in soils and sediments, where mushrooms eventually absorb it. Deer truffle mushrooms (Elaphomyces), for example, are highly effective at absorbing radioactive cesium in clay mineral soils. 

Above: Wild boar with piglets. Image courtesy of EuroNews

Beyond Chernobyl

Despite the radioactive fungi explaining the persistence of cesium in boars, researchers doubt that the Chernobyl accident itself was enough to cause so much radiation, especially in somewhere as far as Germany. After all, the levels of radiation in other organisms affected by Chernobyl had fallen just years after the accident.

A study published in August by researchers at Leibniz University Hannover in Germany traced the levels of cesium in boars not only to Chernobyl but also to toxic nuclear weapons testing that occurred in the atmosphere during the 1950s. Like the nuclear reactor explosion at Chernobyl, nuclear weapons testing released significant amounts of radioactive material into the atmosphere, spreading across Europe. 

To determine how much each source of radioactive fallout contributes to the boars’ radioactivity, the researchers examined different types of cesium isotopes from 48 samples of boar meat across the Bavarian forest. Cesium-137 is found in nuclear explosions and reactors, while cesium-135 is primarily a product of nuclear explosions only (from nuclear weapons, for example). If the radioactive input on the boars stemmed primarily from the Chernobyl reactor, researchers would expect most of the radiocesium in the boar’s tissue to be cesium-137. But, after calculating the ratio of cesium-135 to cesium-137, researchers found high levels of cesium-135, indicating that nuclear explosions contributed significantly to radioactivity in boars. In total, they attributed 10 to 68 percent of radioactivity in the wild boar samples to nuclear weapons testing. 

Above: Hunter displays the head of a wild boar. Image courtesy of Reuters

Future implications of radioactive boars

Researchers from this study suggest that most of the radioactivity from nuclear testing has already been absorbed by the boars. As newer sources of cesium released from Chernobyl infiltrate the soil and are absorbed by deer truffle mushrooms in greater increments, the amount of radioactivity in boars could spike in the coming years. While this would not have a major impact on nearby human populations, the continued radioactivity of boars would keep them off-limits to hunters. Without hunters, the boar population could grow unchecked, eventually reaching the point where boars begin migrating into urban centers.

Ultimately, insights on the prolonged radioactivity of wild boars in Bavaria highlight the legacy of nuclear testing during the tumultuous years of the Cold War, prompting future research into how reckless atomic testing has contributed to other radioactive hotspots around the world.

Will Sun

Will (Trinity '27) is originally from San Jose, California and plans on majoring in Biology. In his free time, he enjoys collecting keychains, playing basketball, and going on walks.

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