Bursting lakes
In the next decade, 24 of Bhutan's glacial lakes are expected to burst their banks spilling millions of litres of water into the valleys below.
When it happens, entire villages, and the people living in them, could be washed away.
Lyonpo Sangay Ngedup, the country's agriculture minister, said: "It is so frightening that I can't even imagine.
"If these lakes burst our valleys will be completely inundated and all these fields you see will be underwater.
"Loss of lives and property and untold misery will come about and this is absolutely unthinkable."
Precarious journey
To reach the source of the problem involves a journey few people have ever undertaken.
"When I see the water levels rising I am so worried that it will come again and this time will cause major destruction to this country"

Phuntsho, village elder
And considering Bhutan does not even have its own helicopter, it is a very rare and somewhat challenging flight.
A precarious climb high over the clouds takes us to the peaks of the Lunana valley, some 6,000 metres above sea level.
Scientists know the picturesque lakes I can see before me are the result of an alarming fact - Bhutan's glaciers are melting faster than ever before.
With me is one of the world's leading geological experts.
Few people know more about Bhutan's mountains and glaciers than Karma Kuenza.
Kuenza says: "They're retreating by 30 to 35 metres per annum."
From the ground it becomes evident that some are already full to the brink.
Small overflows relieve a little pressure but it is clear that it could be a matter of months not years before a massive wall of water hits the valleys below.
Ancient capital
In 1994 a melting glacier led the largest lake in the Lanuna valley to burst its banks.
The waters took over seven hours to reach the villages.
Punakha, one of the kingdom's oldest cities,
is threatened by future flooding
Scientists say it will happen again but this time, because of the erosion and increase in melting snow, the waters will take just 20 minutes to get there.
Lying directly in the path is Bhutan's ancient capital of Punakha.
When flood waters arrived after the Lunana burst, 23 of its people died.
People were totally unprepared for the disaster and now there is fear in the faces of town elders who witnessed that flood, fear of what may come next time.
Phuntsho, a village elder, said: "When I see the water levels rising I am so worried that it will come again and this time will cause major destruction to this country."
Global appeal
Bhutan is desperately trying to stop another glacial outburst but to reach the lakes involves a 10-day trek by foot.
Both Japan and Austria are helping to monitor the rate of melting, record data, lower the water in lakes and put early warning systems in place.
But the burden is not one Bhutan can carry alone.
Ngedup said: "When you put this into the global warming perspective it is even more dangerpous and we are even more concerned about it.
"And what are we doing about? I ask what is the world doing about it? It is what the world has engineered by polluting the atmosphere.
"And my appeal to the world is that we are in danger, you have caused it, you had better come and help and mitigate this problem because we cannot do it alone."