Prettiest birds the hardest hit in Chernobyl

Date:04/10/2007 URL: http://www.thehindu.com/thehindu/seta/

2007/10/04/stories/2007100450091500.htm
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Sci Tech



Prettiest birds the hardest hit at Chernobyl
Birds with bright, colourful plumage registered the strongest decline
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Radiation produces free radicals which damage DNA and other molecules permanently
Four groups of birds which suffered most had high expenditure of antioxidants
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At 01:23 hrs on 26 April 1986, the severest nuclear accident occurred at the Chernobyl Nuclear Power Station in Ukraine. Radioactive materials from the stricken reactor got released over the next ten days. Large areas got heavily contaminated. Initially, vast tracts of pine forests close to the site perished. Over the next few years, the lands recovered their green cover.
Recent reports claimed that animals like wild boar, wolves and moose had flourished in the 40 mile diameter exclusion zone (The New York Times, August 28, 2007).
‘Defying predictions’
“Contrary to the myths and imagery, Chernobyl’s land had become a unique, new ecosystem. Defying the gloomiest predictions, it had come back to life as Europe’s largest nature sanctuary, teeming with wildlife”. Mary Mycio who visited Chernobyl in 1996 described “the lands extraordinary resurrection” in ‘Wormwood Forest, A Natural History of Chernobyl.’
However, Dr. A.P. Moller and Dr T.A. Mousseau who carried out scientific studies of birds noted that population of the prettiest birds with bright, colourful plumage registered the strongest decline with radiation (Journal of Applied Eco logy, July 11, 2007). Population density of species of birds with long distance migration and dispersal and large eggs also declined with radiation level.
“Species richness, abundance and population density of breeding birds decreased with increasing levels of radiation even after controlling statistically for the effects of potentially confounding factors such as soil type, habitat, and height of vegetation” the researchers observed (Biology letters, August 14, 2007).
The researchers used point count census of 57 species of birds at 254 locations in the forests around Chernobyl to establish the relationship between abundance of birds and radiation levels.
Scavengers
Radiation produces free radicals which damage DNA and other molecules in living cells permanently. Antioxidants are free radical scavengers. They protect tissues against radiation damage.
Moller and Mousseau suggested that if antioxidants are a limited resource in the body, individuals with a high expenditure of antioxidants may suffer most from radiation. Pretty birds spent large amounts of carotenoids (these are antioxidants) in their colourful plumes, losing them irrecoverably.
Physical activity
Birds that migrate over large distances spent large amounts of antioxidants during their extreme physical activity. Birds which lay large eggs have lower levels of antioxidants as they deposit most of it in their eggs.
The researchers argued that the four groups of birds which suffered most had high expenditure of antioxidants (Journal of applied Ecology, 2007).
Important implications
“While the present study has implications for the study of animals living in radioactively contaminated areas such as Chernobyl… it may also have important implications for animals elsewhere. There is large variation in natural levels of radioactivity as a result of variation in abundance of radioactive isotopes…There are no studies of the biological consequences of such variations in natural levels of radioactivity, but we suggest that some of the consequences can be predicted from the present study”, the authors claimed.
The researchers expected that individuals of bird species with carotenoid-based plumage to have paler plumage colour in Chernobyl than individuals from control sites.
Similarly, we may expect that ladybird which has the highest number of carotenoids among insects may have paler hues in the high natural background radiation areas (HBRA) of Kerala. The radiation levels in HBRA are relatively low compared to those in Chernobyl.
Lesser range
But ladybirds in HBRA may get exposed to significant radiation doses as they have less range and may be considered to be relatively immobile compared to birds!
Any insect lover can test the hypothesis by carrying out a survey in HBRA for a few days!
Ladybirds may be radiation resistant. Scientists sent C.elgans, a type of round worm, which has been genetically mapped, in the stricken shuttle Columbia to study space radiation effects.
They survived the disaster. Cousins of these survivors may be present in HBRA!
K.S. PARTHASARATHY
Former Secretary, AERB ( ksparth@yahoo.co.uk)
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