Chernobyl Radiation Still Harming Animals

March 18, 2009 -- The Chernobyl disaster, a nuclear reactor explosion and subsequent fire on April 26, 1986, which spewed highly radioactive fallout into the atmosphere, continues to harm animal populations in the Ukraine, according to a new study.

The study, published in the latest Royal Society Biology Letters, presents the most extensive data set ever compiled on the abundance of animals at and around the Chernobyl site. "Abundance" is relative in this case, however, since scientists Anders Moller and Timothy Mousseau determined that insect, bird and other animal populations have dramatically diminished there in the two decades following the disaster.

"Chronic, continuous exposure to low dose radiation appears to be the cause," Mousseau, director of the Chernobyl Research Initiative at the University of South Carolina, told Discovery News.

For three years, he and Moller conducted population censuses on invertebrates at more than 700 sites near Chernobyl. At each site the researchers measured radiation levels, using Geiger counters and aerial scan data. They also counted numbers of bumblebees, butterflies, grasshoppers, dragonflies and spider webs.

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"Our prior work on bird populations at Chernobyl inspired this insect study," Mousseau explained. "While collecting birds, we noticed that grasshopper populations were down. Fruit production was also significantly lowered, and even as we walked through the forest, we noticed few spider webs."

Throughout this latest study, the researchers controlled for natural population reduction factors, such as soil type, habitat and height of vegetation. They found that the abundance of invertebrates decreased with increasing radiation.

The radiation wasn't just higher right at the plant site, either.

Due to factors such as wind direction, the nuclear blast released radiation "in a very patchy manner, so while the highest areas of contamination are closest to the plant, there are also areas of higher radiation quite a ways away from the reactor," Mousseau said.

He and Moller are currently analyzing wolf, fox, rabbit, squirrel and other animal populations. The scientists are not yet ready to release those findings, but the insect population study and the earlier bird surveys suggest that many species "are either absent or in very low numbers in the Chernobyl region."

"Brightly colored and migratory species of birds appear to be particularly sensitive to radioactive contaminants," Mousseau added.

Two processes appear to keep the Ukraine animals in a downward cycle. The first is that radiation could be accumulating within certain species over many generations, through ingestion of contaminated dirt, water and food.