Normal Barn Swallow (a),
while the other pictures show signs of albinism (white feathers; b & c),
unusually colored feathers (d), deformed beaks (e & f), deformed air sacs (g),
and bent tail feathers (h & i).
Images: Tim Mousseau.
Twenty years after the Chernobyl reactor disaster, which released clouds of radioactive particles in April 1986, the uninhabited forests within the 19 mile (30 kilometer) "exclusion zone" around the disaster site are lush and teeming with wildlife, giving the appearance that nature's wounds are healing. However, to the trained eyes of the naturalist, something is seriously wrong here.
In fact, many birds in the area show obvious abnormalities such as deformed beaks, toes, and feathers and unusual coloring (see figure, top). Additionally, the overall abundance of bird populations were noticeably diminished, and individuals were not living as long and were not breeding as successfully as those birds of the same species that live far away. Further, some species that should be present were nowhere to be found or had dwindled to very low numbers.
Upon closer examination, the greatest population decreases were documented for birds with vibrant plumage, and for those species that lay large eggs or migrate over long distances. According to researchers, these particular traits require lots of antioxidants -- molecules that are also essential to protect against radiation damage. Thus, when these other physiological demands diminish the level of antioxidants, this leaves fewer to counteract the effects of radiation.
"Overall we found that population size and abundance decreased," said Timothy Mousseau, of the University of South Carolina in Columbia, SC. "However, a few species actually increased in contaminated areas -- we don't know why, but it could be due to decreased competition in these areas. The take-home message is that there is tremendous variability in the way that different species cope with radiation."
To collect data for this study, Mousseau and his colleague, Anders Pape MÃ¸ller, from the University of Pierre and Marie Curie in Paris, counted more than 1,500 birds at 254 sites in the woods near the reactor, and compared areas with high radioactivity to nearby uncontaminated sites.
First, they found that birds in the Chernobyl nuclear disaster study area have an increased number of genetic mutations. Second, they found that birds with red, yellow or orange plumage based on organic pigments called carotenoids, such as Barn Swallows, were much less abundant in contaminated areas than were less colorful species. Carotenoids act as antioxidants.
Additionally, bird species that produce large eggs and those that migrate over large distances were also very scarce. Further, the researchers noted that some bird populations are apparently sustained only because of continuous migration into the disaster area, that the impact of radiation on those species may be to prevent the establishment of self-sustaining populations.
The reason? The affected bird species had reduced levels of antioxidants. In short, antioxidants are molecules that protect the cells in of body from potential damage by "soaking up" free radicals, but unfortunately, antioxidants are limited.
Free radicals, on the other hand, are not.
Free radicals are a by-product of many natural metabolic processes and result from exercise, such as migration. Eggs also contain high levels of antioxidants that protect the developing embryo. Additionally, it is known that radiation triggers the production of free radicals, which are reactive compounds that irreversibly damage DNA.
Areas throughout the Chernobyl region show variable levels of radioactive contamination. Some areas had very low levels of radiation, but others were so contaminated that the researchers had to wear protective suits and masks.
"Survival and reproduction is depressed in those areas," Mousseau reported.
Interestingly, according to previous work that was recently published in April 2007, most nesting birds can apparently detect the higher levels of radiation and preferentially choose nesting sites where levels are lower.
These data have important implications for people as well as for birds. For example, the high level of abnormalities in these birds suggest that radiation is also the culprit in the higher-than-average levels of health issues found in humans living near Chernobyl, which directly contradicts a report published recently by the World Health Organization. This report blamed social stresses for the various ailments.
"Birds don't drink, birds don't smoke, and they don't suffer the same kind of stresses as humans," Mousseau pointed out.
Mousseau's ongoing research focuses on documenting the effects of low-level radiation over large areas, and examining how ecosystems change and adapt after an event such as the Chernobyl nuclear disaster. Bird species are just one group of animals that the scientists are studying in the area.
Mousseau plans to return to Chernobyl to continue studying the bird populations over time.
This research was published online in the Journal of Applied Ecology.
Determinants of interspecific variation in population declines of birds after exposure to radiation at Chernobyl by A. P. MÃ¸ller and T. A. Mousseau. Journal of Applied Ecology (OnlineEarly Articles). DOI: 10.1111/j.1365-2664.2007.01353.x [free PDF]
MÃ¸ller, A.P., Mousseau, T.A., de Lope, F., Saino, N. (2007). Elevated frequency of abnormalities in barn swallows from Chernobyl. Biology Letters, 3, 414-417 | doi:10.1098/rsbl.2007.0136 [free PDF]. (image)
No pictures in the linked article. The plant life is also very abnormal and the effect on the birds food sources, which at source will be plants even if they eat insects can't be helping.
There may be fewer of the right insects for the birds as well, a lot of pine forest has been replaced by birch and many of the new growth pines are more like large bonsai as well as having changes in the size/shape of their needles.
Though, as this area is likely to be off limits to humans for a long while (even after the radiation levels have subsided to a very low level I can't see people wanting to live there) it might end up having an overall benefit for wildlife.
Sorry, I want to be pedantic. The guy is always called Anders Pape MÃ¸ller (not just Anders MÃ¸ller). I'm not sure why, but there you go. A bit like John Maynard Smith, I suppose.
Good post! Fascinating to think that there is ornithology going on in the post-apocalypse No-Go Zone.
(even after the radiation levels have subsided to a very low level I can't see people wanting to live there)
Many of those in the areas designated unfit for human habitation due to the Chernobyl accident were not resettled. Most of this was due to poor organization and insufficient resources, but some people did refuse to leave. In addition, some of those who were resettled later returned.
See for example page 59 of this report:
4.37 Somewhat better adapted to their situation were the group of people who
remained in their homes in the affected areas. Six years ago, 80% of this group
said that they wanted to leave. In the latest survey, this proportion had fallen to
20%, with 80% wishing to stay in their homes. Many of those who still wanted
to leave were young people who were concerned about the risks involved in
raising children in a contaminated area. Psychologically the best adapted group
were the so called "self-settlers" who had been evacuated and had then returned
despite the restrictions. These people asserted that the threat from radiation was
not as bad as the authorities claimed. They argued that they wanted to be left in
peace in their homes. The Institute found that economic considerations were not
necessarily the over-riding factor. Cultural arguments, such as a desire to live in
the traditional home near to where ancestors were buried, could be very
important, especially for older people.
...but some people did refuse to leave. In addition, some of those who were resettled later returned.
......... Cultural arguments, such as a desire to live in
the traditional home near to where ancestors were buried, could be very important, especially for older people.
Posted by: llewelly
I think that I can understand their feelings about not wishing to leave their homes & lives. I didn't realise that more than a few people had taken this option even some within the heavily polluted areas.
"Interestingly, according to previous work that was recently published in April 2007, most nesting birds can apparently detect the higher levels of radiation and preferentially choose nesting sites where levels are lower."
That is indeed very interesting! The question is, how did they distinguish "choosing" nesting sites from "surviving" nesting sites?
I also wonder how many new species will emerge from the area....
chris, the linked Biology Letters PDF has the image i used at the top. it's on the second page of the PDF.
David, that PDF is inaccessible to me (and you too) but i found that the researchers put up nestboxes 3 km away from the reactor and then compared those areas with high radioactivity versus those with low radioactivity and found that the birds chose those nestboxes in areas with low radioactivity. the nestboxes were located very close to each other, and therefore, were in locations where food and territory quality were very similar, so those factors did not contribute to the birds' nestbox choices. the radioactivity levels were patchy because the radioactive fallout did not settle uniformly.
anyway, you can read more about this study here.
Grrl, my fault for not being clear. I was refering to the article I linked to not the one you linked to.