LONDON (Reuters) - Radiation has affected animals living near the site of Ukraine’s Chernobyl nuclear disaster far more than was previously thought, a study showed Wednesday, challenging beliefs that local wildlife was on the rebound.

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The study showed that numbers of bumble-bees, butterflies, spiders, grasshoppers and other invertebrates were lower in contaminated sites than other areas because of high levels of radiation left over from the blast more than 20 years ago.

The findings challenge earlier research that suggested animal populations were rebounding around the site of the Chernobyl explosion in Ukraine, which forced thousands to abandon their homes and evacuate the area.

Estimates of the number of deaths directly related to the accident vary. The World Health Organization estimates the figure at 9,000 while the environmental group Greenpeace predicts an eventual death toll of 93,000.

“We were amazed to see that there had been no studies on this subject,” Anders Moller, a researcher at the National Center for Scientific Research in France, who led the study, said in telephone interview.

“Ours was the first study to focus on the abundance of animal populations.”

Researchers said they had compared animal populations in radioactive areas with less contaminated plots and found that some were nearly completed depleted of animal life.

“There are areas with an abundance of 100 animals per square meter,” Moller said. “And then there are areas with less than one specimen per square meter on average; the same goes for all groups of species.”

The researchers also found that animals living near the Chernobyl reactor -- which was covered in a protective shell after it exploded in April 1986 -- had more deformities, including discoloration and stunted limbs, than normal.

“Usually (deformed) animals get eaten quickly, as it’s hard to escape if your wings are not the same length,” Moller said. “In this case we found a high incidence of deformed animals.”

The findings challenge the view of Chernobyl as ecologically sound, despite the fact that Ukrainian officials have turned it into a nature reserve, with wolves, bison and bears.

Earlier research into the area ignored the fact that animal populations had grown unimpeded in the absence of humans for many years after the blast, Moller said.

“We wanted to ask the question: Are there more or fewer animals in the contaminated areas? Clearly there were fewer,” said Moller, who has worked on Chernobyl since 1991.

While researchers focused on the 30 kilometer radius around the Chernobyl reactor, the fallout from the explosion covered a vast swathe of Eastern Europe, including parts of Russia, Ukraine and Belarus.

The findings probably apply to those areas as well, Moller said, adding that any decontamination effort was unlikely due to the extent of the fallout.