Between September and June Swiss mountaineer Michel Siegenthaler scaled 60 South American peaks over 6,000 metres – one for every year of his life.
Siegenthaler's aim was not just to reach the top but also to find out about the Andean mountains and the people of the region. But he got more than he bargained for, discovering significant evidence of glacial retreat.
"The retreat of the glaciers is a great concern – something needs to be done," the mountain guide from Valais told swissinfo.
The South American mountains are not new to Siegenthaler. He first set foot on a glacier in the Andes in 1982, when he visited the Cordillera Blanca in Peru. Since then he has visited the region more than 30 times.
He said no technical equipment had been needed to measure the retreat of the glaciers as he could see it with his own eyes.
"I have noticed a very significant difference in the past 23 years. From what I have seen the Chimborazo glacier in Ecuador is certainly melting the fastest."
Siegenthaler, who calls himself "a nature lover who wants to protect the environment for future generations", fears for the future of millions of South Americans once this vital source has dried up.
And he warns that the retreat of the glaciers has not only made the mountains less attractive, it has also made them more dangerous.
"There is more and more gravel, and the rocks are loose. The Rasac mountains in the Huayhuash range in Peru have hardly any glacial zones and climbing there is very dangerous."
Siegenthaler describes his ten-month expedition as an "extraordinary adventure" that took him to the high peaks of Argentina, Chile, Bolivia, Peru and Ecuador. Every mountain he climbed was higher than 6,000 metres.
On his journey Siegenthaler was often faced with difficult situations. In Arequipa he had his hiking boots and jacket stolen from the hotel, and in the Peruvian capital Lima the police frequently checked his personal documents as they thought he was doing something illegal.
"When they found out that I was not willing to give them any money they let me go," he recalled.
But the 60-year-old also enjoyed many positive experiences, not least the new friendships he formed in Huaraz, situated in the Cordillera Blanca – an area which is often called the Switzerland of Peru.
He was also able to get to know many different facets of each country he visited. In Bolivia, for example, he got a taste of the country's political instability as he was faced with riots and roadblocks that made it hard for him to travel around.
"But when I was finally allowed to move I went to one of the most beautiful places in the world: the Salinas de Uyuni, a salt desert 100km wide and 120km long."
In Chile he had a few positive encounters with the local police as they provided him with plenty of information about the mountains and even gave him shelter.
"In Bolivia, Peru and Ecuador there is a huge difference between people who live in cities and those who live in the country. It is certainly like travelling in two different worlds," he said.
Siegenthaler's German wife, who was in charge of finding sponsors, said it was a very difficult task raising funds for the expedition.
"The only sponsors we found were [outdoor clothing and equipment company] Mammut, the Valais Cantonal Bank, our local community and a support group of 75 people," she said.
But even though they could not raise enough money the Siegenthalers were keen to do the trip and paid the rest out of their own pocket. The total cost of the expedition came to SFr200,000 ($157,000).
"It was the most expensive birthday gift but it was fantastic," Siegenthaler said, casting a grateful glance at his wife of 37 years.
Back home in Grimisuat in the heart of Valais, Siegenthaler looks back at a mountaineering spanning nearly four decades.
"In embarking on this adventure I wanted to prove that even at the age of 60 it is possible to do such wonderful things."
swissinfo, Rosa Amelia Fierro
Chile: ten mountains; the highest: Tupungato (6,550m).
Argentina: 27 mountains; the highest: Aconcagua (6,962m).
Bolivia: 7 mountains; the highest: Sajama (6,768m)
Peru: 15 mountains; the highest: Huscaràn Sur (6,768m).
Ecuador: 1 mountain; Chimborazo (6,310m)
The South American Andes are on average 2,000 metres higher than the Alps.
They also stretch over a wider range.
Siegenthaler climbed 40 mountains alone and 20 with two other climbers from Valais.
He has written a book about his ten-month expedition. Carnet de route is only available in French.