Humans may be changing the environment in ways that cause cancer in wild animal populations, propose researchers from Arizona State University. As a way to adapt and thrive, humans are changing the environment in ways that are more suitable for themselves, which is likely having a negative impact on “many species on many different levels, including the probability of developing cancer.”
"We know that some viruses can cause cancer in humans by changing the environment that they live in – in their case, human cells – to make it more suitable for themselves," said researcher Tuul Sepp in a statement.
Published in Nature Ecology & Evolution, the paper suggests humans are contributing to cancer rates in wildlife through radiation release in nuclear accidents, loss of genetic diversity, changes in food sources, and pollution in the forms of microplastics, light pollution, and chemicals.
"Cancer has been found in all species where scientists have looked for it and human activities are known to strongly influence cancer rate in humans. So, this human impact on wild environments might strongly influence the prevalence of cancer in wild populations with additional consequences on ecosystem functioning," said researcher Mathieu Giraudeau.
Previous research found external tumors on wild birds at Chernobyl after the 1986 disaster. The authors believe incidents of cancer in wild animals at other nuclear disaster sites like Fukushima have not been well estimated and is likely underestimated in habitats exposed to the fallout after nuclear disasters.
Reduced genetic diversity may also be contributing to cancer rates in wild animals. Cancer is a multifactorial disease and can cause mutations through inbreeding. Here, the researchers believe endangered animals may have an increased susceptibility to cancer-causing pathogens such as the papillomavirus, which has been observed in many animal species.
Animals are increasingly switching their diets as well. As the rural-urban divide shortens, wild animals continue to scavenge human food. As well, foods used to intentionally bait animals for recreation or conservation purposes often contain toxic contaminants associated with cancers.
That leads us to the suffocating elephant in the room: pollution. Chemical pollution in oceans and waterways has been known to cause tumors in humans and captive animals, and the researchers say there is no reason to believe this isn’t occurring in wildlife as well. It’s not just big oil spills we’re talking about either. Toxic chemicals can be leached off of microplastics – which have been found on nearly every continent and body of water – and can have a carcinogenic effect on wildlife.
So where do we go from here?
"The next step is definitely to go into the field and measure cancer rate in wild populations," said Giraudeau. "We are now trying to develop some biomarkers to be able to study this.”
