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Radioactive Hotspot Harbours Ecosystem
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by ScienceDave | June 8, 2007 at 08:27 am
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Over 20 years ago, just northwest of the capital of the Ukraine, the world saw the worst nuclear accident in its history.
On April 26th, 1986, the Chernobyl nuclear power plant's number four reactor exploded, sending a radioactive cloud across much of Europe. Following the explosion, radioactivity with an intensity equivalent to 500 of the bombs that destroyed Hiroshima at the end of World War II was measured in the atmosphere.
You might think after such a disaster, the ruins of the reactor and surrounding area would be deserted by humans and animals alike. However, there has been a pronounced resurgence of natural wild life to the area (not including "Nuclear Fungi").
Dense forests have reclaimed farm fields and apartment house courtyards. Residents, visitors and some biologists report seeing wildlife - including moose and lynx - rarely sighted in the rest of Europe. Birds even nest inside the cracked concrete sarcophagus shielding the shattered remains of the reactor.
Wildlife has returned despite radiation levels in much of the evacuated zone that remain 10 to 100 times higher than background levels, according to a 2005 U.N. report - though they have fallen significantly since the accident, due to radioactive decay.
Currently, there are two rival schools of thought to explain this re-colonization:
1) Since human activity has nearly ceased in the area, there has not been significant destruction to the budding ecosystem. As a result, the area has become a thriving ecosystem
2) Animals ARE filing into the area, but they are far from thriving. Rather, Chernobyl is more like a "sink", where animals quickly die after arriving.
Ionizing Radiation and Biology
What effects does ionizing radiation have on living cells? Well, as per its name, it "ionizes" matter. An atom is made up of a nucleus (protons and neutrons), which is surrounded by a cloud of electrons that are largely responsible for interacting with the enviroment. When radiation with enough energy (like ionizing radiation) bombards this atom, an electron can be ejected from the grasps of the positively charged nucleus and into the surround milieu, or vice versa.
Why is this dangerous? Well, some elements, like oxygen, are much worse than others when they become ionized. Oxygen has the propensity to form what are referred to as "free radicals". Free radicals are much like a psychopath with a flame thrower, indiscriminately torching a city block. However, much like a SWAT team would contain the disturbed individual, our body uses anti-oxidants to butt the problem.
A Radioactive Threshold?
The above two competing hypotheses are rooted in a more fundamental question in biology. According to Robert J. Baker of TTU, who has researched the Chernobyl ecosystem for nearly 20 years, organisms can withstand a certain exposure of radiation or threshold, before adverse effects are realised.
"Our studies show that a dynamic ecosystem is present in even the most radioactive habitats," they wrote...
...Genetic tests showed Chernobyl's animals suffered some damage to their DNA, Baker and his colleagues reported. But they said overall it didn't seem to hurt wildlife populations.
"The resulting environment created by the Chernobyl disaster is better for animals," Baker told the Associated Press in a phone interview.
Timothy Mousseau at USC disagrees. He has been studying barn swallows that have nested at the cite.
Roughly one-third of 248 Chernobyl nestlings studied were found to have ill-formed beaks, albino feathers, bent tail feathers and other malformations. Mousseau was a co-author of the report.
In other studies, Mousseau...and his colleagues have found increased genetic damage, reduced reproductive rates and what he calls "dramatically" higher mortality rates for birds living near Chernobyl.
The work suggests, he said, that Chernobyl is a "sink" where animals migrate but rapidly die off. Mousseau suspects that relatively low-level radiation reduces the level of antioxidants in the blood, which can lead to cell damage.
"From every rock we turn over, we find consequences," he told the Associated Press in a phone interview. "These reports of wildlife flourishing in the area are completely anecdotal and have no scientific basis."
Mousseau's work and a report released by the National Academy of Sciences National Research Council in 2005 are birds of the same feather. The NASNRC linked low doses of radiation to increased health risks, "A preponderance of scientific evidence shows that even low doses of ionizing radiation...are likely to pose some risk of adverse health effects..." [source]. This would indicate there is no supposed threshold, as Baker argues, but instead that his interpretation of the data is what is at fault.
Critics point out that Baker's work has been funded by the U.S. Department of Energy, which some view as pro-nuclear. Baker defended the government connection, saying, "We have never been asked to come up with any specific conclusions, just do honest work." He also said his work has been peer-reviewed.
Although Baker may be doing honest work, the interpretation of his data comes down to preference: is an increased rate of genetic mutations "OK", if it means saving a piece of the environment for these animals to live?
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Most RecentMost Recommended Comments (1)
at 09:34 on June 8th, 2007
We think fo Chernobyl as a region of devastation, as indeed it was. Life is returning, though, as you point out. Here is a great site by Gamma Girl, a woman who visited Chernobyl on her motorcycle.