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Landscape portrait: A look at the impacts of radioactive contaminants on
Chernobyl's wildlife
Timothy A. Mousseau and Anders P. Møller
Bulletin of the Atomic Scientists 2011 67: 38
DOI: 10.1177/0096340211399747
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Bulletinof theAtomicScientists

IT IS 6 MINUTES TO MIDNIGHT®

FeatureLandscape portrait: A lookat the impacts of radioactive
contaminants on
Chernobyl’s wildlife

Bulletin of the Atomic Scientists
67(2) 38–46! The Author(s) 2011
Reprints and permissions:sagepub.co.uk/journalsPermissions.nav
DOI: 10.1177/0096340211399747
http://thebulletin.sagepub.com

Timothy A. Mousseau and Anders P. Møller

Abstract
The Chernobyl accident of 1986 released vast quantities of radioactive materials and significantly contaminated about 200,000 square kilometers of land. The Chernobyl Forum Report, an initiative of the International
Atomic Energy Agency, suggested that the effects of radiation on wildlife were negligible relative to theimpacts of human habitation, but this position was based on the very limited data available prior to this2006 report. The wildlife of this region has been the subject of extensive study since 2005; since then, research
has found that many birds, insects, spiders, and mammals show significant declines as a probable consequenceof exposure to radionuclides. The best-studied group, birds, shows a 50 percent decrease in species richness
and a 66 percent drop in abundance in the most contaminated areas compared to areas with normal background radiation in the same neighborhood. In addition, mutation rates and developmental abnormalities aredramatically higher, and survival rates and fertility are lower, in regions of moderate to high contamination.
These findings challenge reports in the popular media and the conclusions of the Chernobyl Forum Reportand are of relevance today, given recent interest in returning contaminated lands to agriculture use and therenaissance of the global nuclear power industry.

Keywords
Chernobyl, effects, environment, mutation, nuclear power, radiation, wildlife

he Chernobyl disaster of 1986 provides unique opportunities to
explore the impacts of chronic
exposure to low-dose radioactive contaminants on human health and the environment. Fission products, mostly
cesium 137 and strontium 90, andunspent nuclear fuel, in this case plutonium 239, were distributed across a vastT

geographic landscape (about 200,000
square kilometers, an area 2.5 times
the size of South Carolina) that
includes large parts of northern
Ukraine, southeastern Belarus, andsoutheastern Russia, as well as less but
still significantly contaminated areas of
Scandinavia and Central Europe. At theregional scale, contamination levels are

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Mousseau and Møller

39

highly variable, with background radiation levels sometimes varying by twoorders of magnitude in places just a
few hundred meters apart. This ÒquiltworkÓ of contamination levels, wherehigh and low radiation readings can beobserved relatively close to each other,
but also at distances varying from one tohundreds of kilometers from the reactor
site, allows for highly sensitive analysesof biological effects that can be replicated multiple times across a wide variety of ecological conditions. And,because areas of high and low contamination are distributed both within
UkraineÕs fenced Chernobyl Exclusion
Zone1Ñwhich is within roughly a 30
kilometer radius of the reactor siteÑand
outside of it, there is the opportunity toinvestigate the effects of contaminants
on plants and animals with and without
human co-inhabitants. Serendipitously,
this pattern of contaminant spatial distribution, ecological complexity, anddiversity of land-use is optimal for
addressing questions concerning theimpact of exposure to low-dose radioactive contaminants on biological systems.
There really is no other place on theplanet that provides such potential toaddress fundamentally important questions at a spatial scale that is of relevancefor scientists and policymakers wishing
to understand the effects related to anuclear disaster.
One question that has been posed
repeatedly during the past few years is
related to the alleged abundance anddiversity of wildlife living inside theChernobyl zone. The Chernobyl Forum
Report (IAEA, 2006: 137)2 concluded
that, Ò. . . the populations of many
plants and animals have expanded, andthe present environmental conditions
have had a positive impact on the biota

in the Chernobyl Exclusion Zone.Ó Thisconclusion, however, was based onlimited information from the Western
peer-reviewed literature that wasavailable to the authors of thisinfluential report.3 Despite this, thereportmadeheadlinesÑÒDespite
mutations, Chernobyl wildlife is thriving,Ó (Ravilious, 2006) or ÒWildlife
defies Chernobyl radiationÓ (Mulvey,2006)Ñand the media coverage focusedon the idea that the zone is a thriving
ecosystem with large and vigorous populations of rare and locally exotic species that have returned to this site.
It has even been suggested by the prominent environmentalist James Lovelock(Mulvey, 2006) that locating nuclear
waste within environmentally sensitive
areas could be a way to foster the conservation of threatened ecosystems
because it would tend to deter otherland uses, although this position is notwidely supported.
For the past 11 years, we and our colleagues have systematically addressed
questions related to plant and animalabundance and diversity in relation tocontamination and human habitation in
Ukraine, Belarus, Italy, Spain, andDenmark (our studies in countries outside of Ukraine and Belarus are regionsthat are relatively uncontaminated andthus provide controls for comparison).
The motivation for these studies is aninterest in the evolutionary responsesof living organisms to rapid environmental change rather than any inherent
interest in the impacts of radiation or
nuclear accidents per se. A secondaryinterest has concerned the evolutionof adaptations to mutagenic environments and the life history tradeoffs associated with investment in defensive
mechanisms. A basic understanding of

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Bulletin of the Atomic Scientists 67(2)fundamental ecological and genetic
responses to radionuclides in the environment might provide insights concerning variation among individuals intheir sensitivity and responses to contaminants that could be transferrable,
or at least relevant, for studies concerning impacts to human health.
Although there is extensive literature,primarily from Russia, concerning
genetic damage and radionuclide movement in the environment (GerasÕkin
et al., 2008; Yablokov et al., 2009), there
has been relatively little scientific studyof the biology of the Chernobyl ecosystem by Western scientists. This point
also underscores the fact that claims
for the Chernobyl ecosystemÕs biological health have been largely based on
anecdotal observations (often by journalists or other non-scientists) rather
than any systematic, population-based
scientific study. Consequently, we havefocused much of our effort on a series of
ecological studies conducted over a 5 to
10-year period with the explicit objective of testing the hypothesis that a
nuclear accident like Chernobyl could
actually have a positive impact on wildlife, as suggested by many popular writers and a few scientists.4 Althoughmany uncertainties still exist concerning
the broader impacts of these studies, thesimple results are unambiguous: The
areas of Ukraine and Belarus withhigher radiation have fewer animals(both in terms of abundance andnumber of species); survival andreproduction of many species are
reduced; sperm from many bird species are abnormal and have reduced
swimming
ability;developmental
abnormalities, like birth defects, arecommonplace; and DNA mutation rates
are high.

The barn swallow as anindicator species
One of the first studies to examineÒChernobyl effectsÓ used a popularavian model species, the barn swallow,
Hirundo rustica (Ellegren et al., 1997).
This bird has a near global distribution
and has been the subject of many ornithological dissertations since 1976.5 In
other words, much is known about thisbirdÕs biology, making it an excellent
candidate for ecological research.
Ellegren found that mutations that
occurred in the germline were elevatedin swallows from the Chernobyl region
by a factor of 2 to 10, depending on thetype of DNA that was examined.
Germline mutations are of particularconcern in that they occur in the sperm
or egg and hence are transmitted fromone generation to the next and may
accumulate within a lineage, as opposed
to somatic mutations (also known asÒacquiredÓ mutations) that occur inbodily tissues and are usually not transmitted to offspring. Since this report was
published by Ellegren in 1997, many
additional studies have revealed similar
patterns of elevated mutation rates in awide variety of plants and animals,
including humans, living in the region(M¿ller and Mousseau, 2006; Yablokov
et al., 2009).
Recent studies using the barn swallow
have shown significant impacts onsperm, with direct observations ofdamage to DNA, and effects on spermmorphology and behaviorÑeffects that
could have direct implications for bothmale reproductive success and transmission of genetic mutations to offspring (Bonisoli-Alquati et al., in press;
M¿ller et al., 2004, 2008). For example, it
has been reported that sperm from male

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Mousseau and Møller

41

barn swallows collected in moderately
contaminated areas of the Chernobylzone can have upwards of 40 percent
deformed sperm as compared to control
areas in Ukraine and Spain, where lessthan 5 percent is typical. Also, there is adirect relationship between the level ofbackground contamination and frequency of deformed sperm (M¿ller
et al., 2004). Although not directly
tested, it is likely that these observations
concerning sperm may be related toreduced levels of egg viability andchick survival that have been reported
in Chernobyl (M¿ller et al., 2005) since
it is well-known from human fertility
studies that defective sperm can be acause of reduced fertility.
Barn swallows, like many birds andother animals, display a behavior
known as Òreproductive philopatry,Ó
whereby adults will return to the samegeneral place, often the same nest, tobreed for as long as they are alive (usually one to three years). This allows theresearcher to place a numbered band on
the birdÕs leg for identification to track
the birdÕs survival. In essence, birds that
do not return to the nest site the following year can safely be presumed to havedied during the interval. This feature of
their life history permits very sensitive
estimates of mortality and longevity,
which, when combined with variationin environmental conditions, permits
direct tests of the impacts of contaminants on individuals living in highly
radioactive areas. Using this approach,
we discovered that barn swallows
living in moderately contaminatedregions of Ukraine were more likely todie following exposure than birds living
in relatively ÒcleanÓ areas of Ukraine,
Spain, or Denmark (M¿ller et al., 2005).
Chernobyl barn swallows had a 28

percent chance of surviving until the following breeding season, while morethan 40 percent of birds in clean partsof Ukraine and more than 45 percent ofbirds in uncontaminated Spain typicallysurvive from one year to the next. It is
important to note that this estimate of
impact on swallow survival is likely to
be very conservative in that this study
only included populations where sufficient numbers of birds were living, a prerequisite for reliable statistical analyses.
In many areas of the Chernobyl zone,
especially areas of high contamination,
barn swallows are so rare as to preclude
their study or use in rigorous studies of
population demographics.
In addition to our findings of genetic
damage and reduced individual survival
rates, these population studies of barnswallows demonstrated one additional
pattern of effect that is likely of significance to the general question: barn swallows from contaminated areas are far
more likely to display unusual developmental abnormalities not often found inÒcleanerÓ areas (see Figure 1; M¿ller
et al., 2007).
Birds in contaminated areas weremuch more likely to display patches ofalbinistic or deformed feathers and aberrant plumage patterns, in addition to avariety of other deformities including
tumors on the feet, beak or head, anddeformed toes, beaks, eyes, and feathers.
If one superimposes the frequencies ofabnormalities on a map of Europe showing levels of contamination on a continental scale, it is tempting to suggest a
relationship whereby the high frequencies are found in Ukraine and Belarus(about 20 percent), intermediate frequencies are seen in Northern Italy and
Denmark (4 to 5 percent), while thelowest numbers (less than 2 percent)Downloaded from bos.sagepub.com by Mindy Kay Bricker on March 3, 2011

42

Bulletin of the Atomic Scientists 67(2)Figure 1. Photos of morphological abnormalities from barn swallows living near Chernobyl. a. normal male. b”d.
albinistic feathers on head, throat, and beak. e. tumor on beak. f. deformed lips. g. deformed airbladder. h. extreme tailfeather asymmetry. i. bent tail feather and high tail asymmetry.
Source: Møller et al., 2007; copyright TA Mousseau, 2007.

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Mousseau and Møller

43

are seen in a Spanish population wherecontaminants due to Chernobyl are
not found.

How bird studies demonstratevariation in radiosensitivity
To address the possibility that swallows
are somehow unique in their response tocontaminants, in 2006 we initiated aseries of ecological studies of the entire
forest bird community in contaminatedand control areasÑin other words, allbirds in specific patches of forestÑin
both Ukraine and Belarus that included
sites both within and outside the fenced
Chernobyl zone. The basic protocol was
simple and involved walking a series oftransects through these areas, stoppingat regular intervals (usually 100 meters),
recording an exact location (using GPS)and a localized background radiationlevel, and counting the numbers and species of birds at each spot during a periodof five minutes. A total of 726 standardized point counts of breeding birds weretaken over a four-year time frame(2006”2009). This is a standard protocol
for ornithologists interested in ecological questions (i.e., distribution and abundance of species) and has been found by
the authors and many others (Bibby
et al., 2000) to be a highly repeatable
and reliable method for bird population
censuses.
The results of these surveys were
unexpected and overwhelming: In contaminated areas, there were fewer than
50 percent of the expected number of
species and the total abundance ofbirds was less than one-third of that
expected (M¿ller and Mousseau, 2007a,
2007b). A more detailed analysis of individual speciesÕ responses indicated that
not all species were negatively affected,

and in fact a few showed increased numbers in radioactive areas. It was foundthat species that engaged in long-distance migration (as is common inbirds), species that were brightly colored (usually red or yellow), species
that tended to feed on insects at thesoil surface, and species with particularly large eggs were the most likely to
be missing or in low numbers in contaminated areas. In addition, related surveys
found that birds of prey were also foundin lower numbers in highly radioactive
areas, although our data indicate that
populations of raptors are presently
rising in ÒcleanÓ areas both inside andoutsidethezone(M¿llerandMousseau, 2008).
Overall, the data concerning bird biodiversity and abundances, the first of
their kind from the Chernobyl region,
were unequivocal in demonstratinglarge negative and dose-dependent
effects of radioactive contaminants on
bird populations and communities.
Currently, one can only speculate as tothe exact mechanisms underlying variation among species in radiosensitivity.
However, it seems possible that theavailability of antioxidants (or lackthereof) may play a role in determining
the ability of an individual to manage themutagenic effects from ingested radionuclides. It has been established that
long-distance migrants may arrive on
their breeding grounds depleted of antioxidant reserves (Ninni et al., 2004) andthat brightly colored species often utilize antioxidants (i.e., carotenoids) to
produce yellow and red feathers, andthus both groups may not have theseantioxidants available for radioprotection. Birds with large eggs are known toallocate large amounts of carotenoids tothe yolk, while birds feeding on soil

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44

Bulletin of the Atomic Scientists 67(2)invertebrates may be receiving particularly high doses of radionuclides as aresult of dietary preferencesÑand boththese factors may result in depletion ofantioxidant defenses against oxidative
stress related to radionuclides.

Mammals, bees, butterflies,
and spiders
Of course it is possible that birds as agroup represent a particularly vulnerable class of organisms, given their very
high metabolic rate, frequent reliance on
antioxidants for plumage coloration,
large investment in egg production, andaerial life history. For this reason, in2006 we initiated a series of ecologicalsurveys designed to count common
groups of insects, spiders, amphibians,
reptiles, and mammals in a manner
similar to that employed for the bird
counts, except that mammal populations
were surveyed during the winter byidentifying and counting footprints on
the ground following fresh snowfall(M¿ller and Mousseau, 2011). Insects,
including bees, grasshoppers, butterflies, and dragonflies all show significant
declines with increasing backgroundradiation levels inside the zone(M¿ller and Mousseau, 2009). Althoughamphibians and reptiles also show
signs of significant population declines
in contaminated areas, the sampling
method used for this study was notvery effective at detecting them, and further research will be required to develop
an understanding of how the contaminants affect these groups (M¿ller andMousseau, 2011).
Perhaps the most provocative finding
from this collection of studies relates tomammal abundances. Most of the media
reports, such as those cited at the top of

this article, were inspired by suggestions
from journalists, tourists, and the occasional scientist that mammals, especiallylarge mammals like moose, deer, wolves,
and wild boar, are thriving in the heart of
the Chernobyl zone. These reports are in
opposition not only to the results fromthe bird, spider, and insect studies
described here, but also to our many
months of observations inside the zone,
over a period of more than 10 years, that
there is in fact a relative paucity of large
animals despite the absence of post-disaster human impacts (e.g. hunting).
This is a concern in that it is not
unusual for visitors to national parks
or wildlife refuges to be confronted by
the consequences of unchecked population growth: Most organisms are capableof quickly overpopulating their habitats
once predators (very often, humans) areremoved from the ecosystem. Such is
not the case for Chernobyl, where thesighting of a large mammal is in fact
a very rare event. However, it is ouropinion that disagreements of this sortare best addressed with scientificallydesigned experimental approaches thatgenerate data that can be used to rigorously support or refute the underlying
hypothesis. To this end, we conducteda survey of mammals that took advantage of the relative ease of species identification provided by examination offoot tracks in fresh snow (Bang et al.,2007). Using standard ecological methods (Becker et al., 1998), it was foundthat mammal abundance was significantly lower in contaminated areas of
the Chernobyl zone and that variation
in background radiation levels explained
about 20 percent of the variance inmammal numbers, which in this field
represents a very high level of predictability (M¿ller and Mousseau, 2011).

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Mousseau and Møller

45

At this time, it is not known with any
precision if mammal abundances inclean areas within the zone are significantly higher than those outside thezone, but the data unequivocally demonstrate that abundances decline significantly in a dose-dependant mannerwith increasing background radiationlevels.

Conclusion
With few exceptions, wildlife within the
Chernobyl zone show a strong pattern of
declining abundance and species richness in proportion to background radiation levels. This pattern is also observedin contaminated regions of Belarus,
where human populations have returnedand agriculture is practiced, thus precluding human influences as a sourceof the pattern of variation observed
inside the fenced Zone of Alienation in
Ukraine. The broader impacts stemmingfrom these findings include the assessment of risks and hazards related tohuman repopulation of contaminatedareas and the use of the land for agriculture, forestry, and tourism.
The genetic and ecological studies ofnatural populations presented here
point to the possible perils of mutation
accumulation accrued within populations and amplified across generations.
That is to say, the long-term biologicalimpacts of sub-lethal mutagenic environmental contaminants are insidiousand are potentially considerably more
destructive on an evolutionary scalethan lethal exposures because the carriers of the mutations may transmit
them to their offspring, potentially lowering the mean fitness of the entire population. For the moment, such ideas
are purely theoretical and lack strong

empirical evidence, but they warrant
further investigation in the one ecosystem that provides opportunities to test
them: the Chernobyl Zone of Alienation.
Notes
1. This area is also sometimes referred to as theÒZone of Alienation.Ó
2. Copies of many of the papers cited here
are available from the first authorÕs website(http://cricket.biol.sc.edu/chernobyl),or
uponrequestfrom
theauthors(Mousseau@sc.edu or anders.moller@
u-psud.fr).
3. For the most part, scientific reports from
Eastern European were ignored by the
Chernobyl Forum report authors. For a summary of much of the literature from Eastern
Europe, see Yablokov et al. (2009).
4. Our research started in 2000, but continues
today.
5. For example, a search on ISIÕs Web of
Science shows 864 papers published since
1976 that include Hirundo rustica as a
keyword.

References
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Author biographies
Timothy A. Mousseau is a professor of biological sciences, the associate vice president
for research and graduate education, and thedean of the graduate school at the Universityof South Carolina, Columbia, USA.
Anders P. M¿ller is a director of researchwith the Centre National de la Recherche
Scientifique, in Paris.

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