By Elliott Gotkine
BBC correspondent in Tierra del Fuego, Argentina
Beavers have created a landscape of dead trees
At the end of the world, a sky-blue stream sweeps down from an ice-glazed mountain on its way to the Beagle Channel.
Wild horses chomp nonchalantly on lush, green bushes. Tourists gawp at a submerged forest as a beaver glides gracefully among the trees.
This is the Argentine part of the island of Tierra del Fuego, which is shared with Chile. It looks like an ecological paradise.
But on closer inspection you realise that something isn't quite right.
"All those trees you see," says Bismark, our tour guide, as he points towards a dammed river that is now a lake, "they're all dead. And this is because of the beaver."
Inside the beaver-built body of water there are hundreds of petrified-looking trees. They are dried-out, grey and naked.
Each lake is usually formed by just two beavers. They chop down trees with their razor-sharp teeth and use them to dam rivers.
They do this to protect themselves from possible predators - even if there aren't any - and to give them easier access to food, primarily tree bark and other vegetation.
Now, if you consider that there are estimated to be up to 250,000 beavers on the island, you begin to get an idea of the environmental havoc being wreaked here by the world's second-largest rodent (the capybara is number one).
Yet beavers are not native to South America. Around 50 of them were introduced here from Canada in the 1940s. Argentina's then military rulers hoped that they would multiply and create a fur industry - in earlier centuries beaver pelts were among the most valuable in the world.
The beavers certainly multiplied. But their fur was out of fashion.
With no natural predators and an abundance of food, these tree-eating herbivores thrived - so much so, that beavers are now officially considered a plague.
Loggers fear for livelihood
Local loggers have borne the brunt of the beaver plague.
Manuel Berbel owns a timber-yard just outside the island town Tolhuin. Dressed in a red lumberjack shirt and speaking through his handlebar moustache, he told me he had been logging here for 20 years.
During that time, he has seen large chunks of his livelihood ravaged by beavers. They also pollute the water, he told me, and make roads impassable. The situation, he says, is getting worse every day.
"The number of beavers keeps growing and growing," he said, as he pointed to the land he rents from the government.
"The day's going to come when they're going to be the only ones left here and we're all going to have to leave. It will become the island of the beavers." He chuckled stoically at the thought, before continuing his anti-rodent rant.
"And I want to tell people in other countries, who say what a cute animal the beaver is, to think before introducing it. Its only natural predator is the bear. So they should have brought the bear too."
To control the population, local hunters used to be paid a beaver bounty of $1.50 for every dead rodent.
There were claims that 20,000 were killed, but little proof. So the payments were suspended last year, and the beavers are now multiplying at an annual rate of 20%.
"We've decided to launch a controlled killing campaign in some specific beaver colonies and to find possible uses for the animal's skin and meat," says Sergio Luppo, the island's top environmental official. "We want a controlled management of the population."
Tourists pay to see them
For some, though, beavers have been a boon.
The tourists being led by Bismark through the labyrinth of desiccated trees have paid a local travel agency more than $30 a head in the hope of snatching a glimpse of a wild beaver. In the National Park, they have a "beaver trail", and there are plans to build a second one.
There are even improbable sounding plans to harness the pent-up energy in beaver dams to extract hydro-electric power.
Most of the people here have over the years resigned themselves to sharing the island with the beavers. But there could be worse to come.
The rodents have multiplied so prodigiously that they're running out of space.
It is feared they could soon swim cross the Straits of Magellan and colonise the mainland. And if that happens, Argentina's Great Beaver Plague could go continental.