Chernobyl: A field trip to no man's land
"I had nightmares when I first came here," says Andrea. "You feel this sort of constant invisible threat.
"But you do get used to it. Now, I actually quite enjoy these field trips."
Andrea Bonisoli-Alquati, a willowy Italian biologist, is sitting with a team of his colleagues in one of the very few restaurants in Chernobyl.
In this half-empty dingy canteen, while the speakers blare out euro-pop, Andrea is eating dinner on the first evening of a six day scientific excursion to the 30km exclusion zone that surrounds the infamous Chernobyl nuclear power plant.
He is one of an international team of a dozen researchers who are here to study the ecosystem that was left behind after the 1986 accident.
In the 25 years since the accident, which showered the area with radioactive dust, the town of Chernobyl and the main roads through the zone have been cleaned up.
These days, many areas of the zone are deemed safe enough for tourists. But this team is deliberately heading into the overgrown pastures and forests - areas that are most contaminated and therefore most dangerous.
They come here to find out what the impacts are of a nuclear accident on the life that is left behind.Post-apocalyptic zone
Tim Mousseau, the affable, outdoorsy Canadian scientist who is leading the team, says this place is an irresistible natural laboratory.
- The dust did not settle evenly after the 1986 explosion
- This means the Chernobyl exclusion zone is a patchwork of relatively clean and very contaminated areas.
- In the cleanest areas, you would receive the same dose over several weeks that you would receive in an average year in the UK.
- Two days in the most contaminated parts of the Red Forest would be equivalent to the dose you would receive from a medical CT scan.
He and his colleague, the Danish ecologist Anders Moller, are in their 12th year of working together in the zone.
The team starts its first day at 4.30am. Travelling across the zone in the soft early morning light is eerily quiet and beautiful. It seems as if nature has finally won the battle here.
But, according to Professor Mousseau, appearances are deceptive.
"Many people come here expecting to see a lunar landscape, so when they see trees, and birds and a few mammals, they're surprised.
"They think, 'ah well maybe it's not so bad'.
"But what we're finding is that there is a significant impact on both the population and the biodiversity - the number of species - in the zone. And it's directly proportional to the level of contamination."
But this is one side of a polarised scientific debate.
Dr Jim Smith, a radioecologist who has been studying Chernobyl for 20 years, says that the evidence from laboratory studies suggests there is no significant damage to wildlife.
"Lab studies are limited, though," he says. "They obviously cannot study animals in their natural environment and often are carried out over short periods of time."
Dr Smith has also carried out his own studies focusing on aquatic ecosystems in the zone. Strangely, he found the greatest biodiversity - the highest number of species - in the most contaminated of the zone's lakes, Glubokoye.
Professor Mousseau says that he has found just the opposite, not just for birds, but also in mammals and insects.
"The effects are dramatic," he says.
"In the highly contaminated areas, we see fewer than half as many species as there are in the cleaner parts of the zone."
The fact that the zone is a patchwork of relatively clean and very dirty areas makes the picture even more confusing.
Driving through the zone, you can see misshapen pine trees - their growing tips are damaged by radiation - that have formed gnarled, nightmarish shapes.
But there are also stretches of lush forest. On one occasion, the team even spots a moose wandering through the overgrown pastures.Poisoned wilderness
On the second morning, the team heads for a spot that is just a few kilometres from the power station.
In the shadow of a monolithic but defunct cooling tower, they set up their bird-catching nets.
They come back to the same places each year to string up nets across the windows of abandoned buildings and through stretches of the forest to catch and study the birds that inhabit the zone.
Under the shade of an ash tree, they set up their "lab camp".
A tent with picnic tables serves as a laboratory bench. And a noisy petrol generator is powered up from time to time, to run a microscope and other laboratory equipment.
The troop of research assistants checks the nets regularly, gently disentangling each bird. Professor Mousseau and Dr Moller examine each one carefully, taking measurements as well as blood and sperm samples.
Each day is a 16-hour outdoor data-gathering mission.
And the data has fuelled dozens of publications in scientific journals, including the Royal Society's Biology Letters.
Dr Sergii Gashchak, a researcher at the Chernobyl Center in Ukraine, has criticised the team's findings. He says that the lack of human influence means that wildlife is thriving in the zone.
Dr Smith agrees.
"Now the people have moved out," he says. "It's clear that everyday human occupation and activity did much more damage than the contamination left by the accident.
"Whether radiation is damaging wildlife in Chernobyl is still an open question."
As Professor Mousseau points out, there is still no comprehensive, published census of animals in the zone to answer that question.Silent forests
The team's latest studies on birds suggest that the contamination is linked to some unusual genetic effects.
A study published earlier this year in PLoS One showed that birds in the exclusion zone have smaller brains.
One member of the team, biologist Gier Rudolfsen from the Norwegian Radiation Protection Authority, has been focusing on how the male birds' reproductive organs might be affected.
Sperm production is thought to be very sensitive to radiation.
The constant unzipping and replication of DNA required to produce millions of sperm cells each day means there are many opportunities for the biological assembly line to be broken.
So far, in work that is yet to be published, that is exactly what the researchers are finding.
"The strongest effects seem to be on sperm production," says Dr Rudolfsen.
"In the most contaminated areas, male birds produce less sperm and if they produce sperm, it has a slower swimming speed."
So it seems likely that the birds' fertility is badly affected; and, Dr Rudolfsen says, most species show the same effects.
It is only the fourth season that he has been here with the group, taking these reproductive measurements.
"It's a very special feeling when you come to the Chernobyl zone," he says.
"The contamination is invisible, but you do observe it indirectly by the fact that there are fewer birds singing in the morning.
"In the Red Forest, you don't get the beautiful morning concert that you would expect in a forest like this," he adds.
On the final evening of the trip, the team gathers at the viewing platform close to reactor number four.
Twenty-five years on, it is now covered with scaffolding and a rusting, leaking sarcophagus. A team of construction workers arrives each day to continue work on the permanent structure that, it is planned, will eventually protect and physically stabilise the reactor.
Dr Mousseau gathers the team for a group photograph - posing in front of the huge, rusting hulk of a Soviet calamity.
"It's an adventure coming here," says Dr Mousseau. "But I'm always happy to leave.
"It's very demanding work and there's a certain element of hazard associated with it."
Still, he and his colleagues will be back later in the year to continue their work.
Their next trip, though, will be to Fukushima. The scientists hope to embark on similar studies in the exclusion zone there.
"This place gives us the opportunity to do research that can't be done anywhere else in the world.
"It's extremely important for us to repeat these studies. We'll definitely be back next spring."