By Damian Grammaticas BBC Moscow correspondent

Since the collapse of the Soviet Union, birthrates and male life expectancy have suffered sharp declines. The effects are particularly visible in rural areas, where populations have been dying off or moving to towns and cities.

The Russian heartland is being reclaimed by the woods

Five hours' drive north east of Moscow, you can see the change happening in the Kostroma region, where the problem of abandoned villages has reached epidemic proportions.

This is the ancient heartland of Russia. The Volga river winds through a region of rolling hills and expansive forests. Centuries ago, Russians cleared patches of Kostroma's woodland for their farms.

Dotted here and there are the old villages where they made their homes. Houses built from wooden logs cluster in clearings in the forest. Many are picturesque places, but they are emptying and the life is ebbing out of them.

Wooden hearts

Isupovo is typical of Kostroma's problems. There used to be around 30 families in the village, their log cabins stretched along a hillside. Isupovo has a pond surrounded by bulrushes, and a crumbling old church, the cross atop its onion domes hangs at a crazy angle.

Nobody will be left, new people won't come here, there is nothing to do, we old people will just die Tatiana

Vasily Bykov is the last person left in his village. Everyone else has abandoned Isupovo. When I arrived, Vasily stumbled out of his home to greet me, surprised to see a visitor.

Vasily is now an old man, with thick, bushy moustache. He's lonely here, but he has no relatives and nowhere else to go.

Ruefully, Vasily told me: "There is an old song called My Wooden Village. It's about people who leave their village, people who have wooden hearts, they betray the land that fed them. They just leave everything behind."

Vasily showed me where Isupovo used to have two schools, a post office, a church. The old wooden houses are slowly rotting away, roofs have caved in, saplings sprout through the floors, and cobwebs hang from the eaves.

Homes hewn from the trees are being reclaimed by the woods.

Last man: Vasily Bykov has no relatives and nowhere else to go

Underlying this change is the dramatic decline of Russia's population. In the decade after 1992 Russia's population fell from 149 million to 144 million, and the problem is getting worse.

The UN's Population Division projects a "medium case scenario" under which Russia's population could drop by another 20 million over the next 20 years. Russian projections of a "worst case scenario" show Russia's population could decline to around 100 million by 2050.

It was in the late 1980s that birth rates in Russia began to fall sharply and death rates to rise. The social shocks delivered by the collapse of the Soviet Union led to poverty and economic crisis. Women began having fewer children, and deaths rates, particularly among men, have climbed dramatically.

Memories

Alcoholism and poor diet, coupled with diseases like tuberculosis and a crisis in health care, have all meant more and more Russian men dying younger. Average life expectancy for a Russian man is now just 59 years.

Many traditional rural buildings are decaying

Its wooden houses are better kept, some have pretty gardens full of flowers in summer. But already they stand next to homes that have been abandoned.

There are only a dozen inhabitants left in Runovskoye, mostly retirees who have been unable to move away.

I find Katerina milking her cow, part of a small herd which is all that is left of Runovskoye's communist-era collective farm.

The rural economy in places like this was already in decline before the collapse of communism. Since then the process has accelerated. Mass migration to towns means only the old remain.

"I don't feel bitter, just sad," Katerina tells me. "We've worked here for nearly 50 years. But we earn so little. I only hope I will have enough money to last me until I die."

Nearby, washing her clothes in the village pond, is Tatiana. She lived in Runovskoye through World War II, and times of famine.

For her, its best days were when Leonid Brezhnev ran the Soviet Union. After this winter she does not believe her village will survive for long.

"Nobody will be left, new people won't come here, there is nothing to do, we old people will just die," Tatiana says.

So hidden in Russia's forests is a way of life that has lasted for centuries, but which is dying off. The result can be seen most starkly in Isupovo, where Vasily Bykov remains the last survivor.

A whole village reduced to just one man and his memories. Soon there will be nothing at all.