In the 33 years since the world's largest nuclear disaster at Chernobyl Power Plant, the area around the abandoned city has become a fascinating laboratory for biologists. In the absence of humans, plants and animals have reclaimed the landscape.

On first glance it seems the wildlife there was thriving. But if you dig a little deeper, according to Canadian scientist Timothy Mousseau, what you see paints a more disturbing picture.

He's been part of a long-term collaboration looking at the effects of prolonged, residual radiation on wildlife.

"We really know very little of the sort of larger landscape-scale ecological and community ecosystem level effects." said Mousseau, a professor of biological sciences at the University of South Carolina, in conversation with Quirks & Quarks host Bob McDonald.

What's happening with Chernobyl's rodents

Mousseau said Chernobyl is the ideal place to study the effects of prolonged radiation exposure because surrounding the city is a 2,600 sq km exclusion zone where human habitation is forbidden. In that zone, the radiation levels vary, making it easy for biologists to compare different levels of radiation effects.

"It's a quilt work of contamination with some areas that are really, really radioactive — some of the more radioactive parts of the world, in fact. In other areas, within a kilometer or two, might be really clean."

It may look like nature is thriving in the absence of humans at Chernobyl, but scientists are finding disturbing underlying injuries from radiation to much of the wildlife in the area. (Sean Gallup/Getty Images)

In Mousseau's most recent study, he wanted to see what impact the varying radiation levels were having on the areas' rodents in terms of their genetic and physiological fitness, as well as looking at their population level as a whole.

"We've been tracking these small rodents," which Mousseau points out are near the bottom of the food chain for animals like wolves and foxes.

"The bottom line is that when you look at what the populations are doing in both the radioactive areas and the non-radioactive areas of the zone, it's very, very clear that the radiation is reducing fertility rates [and] reducing population sizes," added Mousseau.

White storks on road near Chernobyl, Ukraine (Prof. Timothy Mousseau)

Effects on Chernobyl's birds

Of the dozens of scientific papers Mousseau has published on the effects of radiation on the area's wildlife, he said the animals they know the most about the birds.

One of the early questions they were interested in was whether the birds had developed any kind of adaptation to deal with the effects of the radiation.

"We thought, well maybe there is some kind of magical adaptations that allow these birds to tolerate the radiation," said Mousseau. "We went to test that and quickly found out that there was no such evidence of any kind of [direct] adaptation."

Many birds living in zones of higher radiation in Chernobyl have tumours. (Prof. Timothy Mousseau)

Instead, he found the birds, especially in the more radioactive areas, showed many abnormalities:

Change in colouration, particularly with patches of albinism, not seen anywhere else

Genetic damage in many species

Elevated rates of cataracts and tumours

A five per cent smaller brain, linked to poorer survival

Lower sperm counts

Reduced population sizes

"Almost everything we've looked at ends up showing some consequence in the more radioactive areas," said Mousseau.

This chaffinch bird, like many others in Chernobyl, have patches of albinism in their feathers — a trait Prof. Mousseau says is not seen anywhere else. (Prof. Timothy Mousseau)

While the birds haven't shown any direct evidence of a genetic adaptation, he said they've seen indirect effects.

"Some birds make use of melanin for coloration, but they also make use of the precursor to melanin as an antioxidant, which may provide some measure of defence against the ionizing radiation," said Mousseau.

In a study, he found that those birds that seemed to show less genetic damage ended up being a bit lighter coloured.

"It looks like there's a tradeoff in the use of this antioxidant between colouration and defence against oxidative stress or ionizing radiation."

Prof. Timothy Mousseau (right) and Prof. Anders Pape Møller (left) are long time collaborators working to monitor the long term effects of radiation exposure on Chernobyl's wildlife. (Prof. Timothy Mousseau)

Lessons from Chernobyl's radioactive frontier

Now that more than three decades have passed since the initial disaster, there is one fundamental question Mousseau and his colleagues would like answered. Can we separate the effects of the initial high-dose radiation blast — the effects of which may be passed down to their descendants — with the more prolonged low-dose exposure many animals face today?

Mousseau said some of his colleagues have been revisiting some of his older data on birds and mammals in both Chernobyl and Fukushima to try to answer that question.

"The bottom line from these studies is that you can explain an awful lot of the patterns that we see from that historical dose. And the only way that could exist is if there was some message transmitted from one generation to the next."

They're still working on figuring out how that message gets passed down — whether it's changes in the DNA sequence or epigenetic effects that change how DNA gets expressed.

"But it's clear that there's more going on than just the acute exposure effects."