CONTROVERSES NUCLEAIRES !
Bases de données TCHERNOBYL
Dossier "Le paradis ou non pour les animaux?"
1) Chernobyl-based birds avoid radioactive nests
2) For Chernobyl birds, color is a curse
3) Les oiseaux de Tchernobyl
Introduction New Scientist:
   Chernobyl alert
    RADIATION or relocation? A study of birds around Chernobyl suggests that nuclear fallout, rather than stress and deteriorating living conditions may he responsible for human birth defects in the region. People living around the site of the 1986 nuclear disaster in Ukraine have unusually high levels of physical abnormalities and birth defects. The international Atomic Energy Agency has suggested that the abnormalities are caused by the impact of relocation and stress on the population, and Tiimothy Mousseau, at the University of South Carolina, Columbia, wanted to put this to the test. Mousseau and his calleagues examined 7.700 barn swallows from Chernobyl and compared them with birds from elsewhere. They found that Chernobyl's swallows were more likeIy to have tumours, misshapen toes and feather deformities than swallows from uncontaminated parts of Europe (Biology Letters, DOI: 10.1098/rsbl.2007.0136). "We don't fully understand the consequences of low doses of radiation," says Mousseau. "We should be more concerned about the human population." (New Scientist 21.4.2007, p.6)
    Birds in Chernobyl choose to nest in sites with lower levels of background radioactivity, researchers discover, but how they can tell remains a mystery.
1) Chernobyl-based birds avoid radioactive nests
Source ADIT, http://environment.newscientist.com/, avril 2007
00:01 28 March 2007
NewScientist.com news service
Catherine Brahic

    Anders Møller at Pierre and Marie Curie University in Paris, France, and Tim Mousseau at the University of South Carolina in Columbia, US, erected more than 200 nest boxes in the Red Forest, about 3 kilometres away from the nuclear reactor that exploded in 1986.
    Using these artificial nests, they studied at the nesting habits of two species of birds – the great tit Parus major and the pied flycatcher Ficedula hypoleuca – between 2002 and 2003.
    Moller and Mousseau wanted to see if either species would differentiate between nesting sites that had high and low levels of background radioactivity. The patchy distribution of background radioactivity in the area (due to the fact that radioactive material from the explosion did not settle uniformly) meant the nest boxes could be in very similar locations, with similar food supplies, but have widely varying levels of background radioactivity. Levels at some nest sites were as much as 2000 times natural levels elsewhere in the world.

Deformed sperm
    The researchers found that both species had a definite preference for nest boxes with low radioactivity, with the pied flycatcher seemingly more sensitive than the great tit (see chart, bottom right).
    Previous research done by Mousseau and colleagues (Trends in Ecology and Evolution, DOI: 10.1016/j.tree.2006.01.008) showed that higher radioactivity results in lower levels of antioxidants and also deformed sperm in barn swallows around Chernobyl. It therefore makes sense for birds to avoid more radioactive sites.
    "It is not entirely clear exactly how the birds are able to tell which boxes are most contaminated", says Mousseau, adding that determining this will be very difficult without experimental manipulations.

Wildlife boom
    A spokesperson for the Royal Society for the Protection of Birds told New Scientist that the study is interesting, but points out the unexpected benefits of the Chernobyl explosion. Reports show that the large human exclusion zone around the site has led to a boom in animal populations, including eagles, wolves and bears.
    "Whatever effect the radioactivity is having, it seems to be less of a threat than human activities, such as agriculture," said the spokesperson.

suite:
    "There have been few rigorous scientific analyses of background radiation and the natural abundance of species," responds Mousseau. "But every rock we turn over, every survey we do, we find some previously unreported effect of background radiation."

Immigrant influx
    Mousseau believes that the reports of sustained animal populations around Chernobyl mask fluctuations within the populations.
    He says studies he has carried out looking at where the barn swallow populations in Chernobyl come from suggest that "the populations are mostly sustained by immigrant birds", rather than birds returning to their nesting sites as they normally would.
    So an overall picture showing constant population size could hide the fact that the local population is dwindling but being constantly replenished by neighbouring ones.
Journal reference: Proceedings of the Royal Society: B (DOI: 10.1098/rspb.2007.0005)


The nest boxes were all in the Red Forest, a few kilometers from Chernobyl's reactor 4 which exploded in 1986 (black dots, bottom left) (Image Proc. Roy. Soc. B)


The nest boxes were mounted on tress, between 1,5m and 2m above the ground (Image: T. Mousseau)


Pied flycatchers (B) were more picky about avoiding nest boxes with higher levels of background radioactivity than great tits (A) (Image Proc. Roy. Soc. B)
2) For Chernobyl birds, color is a curse
    Gaudier species seem to be more affected by radioactive fallout. Scientists say that's because they have fewer antioxidants to spare.
 
By Amber Dance
Times Staff Writer
July 14, 2007
http://www.latimes.com/

     Radioactive fallout near the site of the 1986 Chernobyl nuclear power plant disaster in northern Ukraine has reduced populations of brightly colored birds more than those of their drab cousins, scientists reported this week.
     Growing those vividly colored feathers uses up a lot of antioxidants, which are also needed to fight radiation damage.
     The research, published online Wednesday in the Journal of Applied Ecology, suggested that such birds don't have enough antioxidants left over to thrive in highly contaminated areas.
     Radiation causes the production of free radicals, reactive compounds that can damage DNA. They are also made during normal existence, as a result of exercise and other natural processes.
     Antioxidants mop up free radicals to defend the body, but there is a limited supply of the protective molecules.

      The forest surrounding Chernobyl, where an accident released clouds of radioactive particles, might look like a wildlife preserve, said study author Timothy Mousseau, an evolutionary biologist at the University of South Carolina.
     But to the eye of a trained naturalist, something is clearly wrong. Many birds have abnormalities, such as deformed beaks or bent tail feathers.
     To analyze the wildlife populations, Mousseau's team went into the forest and counted birds at 254 sites.
     Some spots had very low levels of radiation, but others were so contaminated that the scientists had to don protective suits and masks.
     Brightly colored birds such as orioles and blue tits were less numerous in the highly contaminated sites. "Survival and reproduction is depressed in those areas," Mousseau said.
     Mousseau hopes to return to Chernobyl to track the bird populations over time. Armed with this information, he said, "we can develop better predictors of the effects of these kinds of accidents."
     Other species that use high levels of antioxidants, such as those that lay large eggs or travel long distances, were also affected.
     Migrating birds use up antioxidants because of physical activity, and eggs tend to contain high levels of the defensive molecules.
     amber.dance@latimes.com
3) Determinants of interspecific variation in population declines of birds
after exposure to radiation at Chernobyl
http://www.blackwell-synergy.com
( ... )
     These findings highlight the importance of antioxidants for understanding the ecological consequences of radiation on the abundance of free-living animals, showing that species using large amounts of antioxidants will be particularly susceptible to the effects of low-level radiation.
( ... )
Les oiseaux de Tchernobyl
     L'impact sur la faune de la catastrophe de Tchernobyl n'a pas été identique sur toutes les espèces.
     L'étude signée ce mois-ci dans la revue scientifique britannique Journal of Applied Ecology montre que les radiations ionisantes émises lors de la catastrophe de la centrale nucléaire de Tchernobyl, en 1986, n'ont pas été subies de la même manière par toutes les espèces ornithologiques.
     Vingt et un ans après l'accident, Anders Moller (université Pierre et Marie Curie, France) et Thimithy Mousseau (université de Caroline du Sud aux Etats-Unis) ont découvert que les espèces les plus bariolées, celles qui entreprennent d'importantes migrations ou encore, qui pondent les plus gros oeufs par rapport à leur taille ont beaucoup plus décliné que les autres. Une affirmation étayée par l'examen de quelque 1.570 oiseaux relevant de 57 espèces différentes.		      Cet intrigant constat s'expliquerait, selon les deux hommes, par l'usage que les oiseaux font de leurs antioxydants: ces composés chimiques qui aident les organismes vivants à se protéger contre les radicaux libres.
     «Chez les oiseaux, une bonne partie des antioxydants passe dans les oeufs. Plus ces oeufs sont gros, comparativement à la taille de l'espèce, plus l'oiseau se défait d'une partie importante de ses protections naturelles», estiment les deux hommes. Chez les espèces colorées, principalement dans les tons rouges, jaunes et orange, le raisonnement est identique. «Pour synthétiser ces coloris, les oiseaux puisent dans leurs réserves de caroténoïdes, un de leurs antioxydants», précisent les chercheurs.
     Au hit-parade des espèces qui ont le plus souffert, les deux écologistes pointent tout particulièrement le loriot, la mésange, les cailles, les merles et les hirondelles.