On a clear day, Chile’s towering 5,400-metre (17,700-foot) El Plomo mountain can be seen from the capital, Santiago. The glacier-capped Andean peak has been climbed and revered for centuries, with the Incas carrying out human sacrifices at the summit.

The route to the top is still the same path paved by the Incas, with archaeological remnants scattered along the way. An Incan mummy was found near the summit in 1954, perfectly preserved due to the mountain’s dry and cold conditions.

Now the mountain is crumbling. Rising global temperatures due to climate change have led the glacier to retreat and the permafrost to melt. New lagoons have formed and ruptured, landslides have injured climbers and massive sinkholes have opened up, breaking up the ancient path to the summit.

“Every year things are changing more. Every year there’s more sadness,” said Francisco Gallardo, a 60-year-old muleteer who has worked on the mountain since he was 14, at the Federacion base camp, about 1,300m (4,265ft) below the summit.

Gallardo said his family has been working at El Plomo for generations, but he thinks they have about a decade left before they are forced to move.

“We’re going have to go somewhere else, see what we can do, maybe head south,” he said.

Just a few years ago, the last push to the summit required a glacier traverse. Now, the final ascent is a rocky hillside. Gallardo said mules used to be able to reach another camp about 500m (1,640ft) further up, and he remembers mules feasting on grass around the base camp.

“The changes we’re seeing are unprecedented in recent human history,” said Pablo Wainstein, a civil engineer who has studied Andean and Arctic glaciers and permafrost for more than two decades.

The Andes present different types of frozen formations, including covered and uncovered glaciers as well as rock glaciers, with the latter composed of a mix of debris and ground ice. Covered glaciers react more slowly to changes in climate than uncovered glaciers where the ice is exposed.

At high altitudes, the mountains may also have a layer of permafrost, defined as ground with temperatures below freezing for more than two years. Where ice is present in permafrost, it may bond soil, gravel and sand together.

“If permafrost degrades, it’s not ‘cementing’ anymore the ground and it leads to more rockfalls in mountainous terrain,” Wainstein said, adding that permafrost change is harder to study since it involves the thermal state of the ground and is not visible on the surface.

The Andes are home to approximately 99 percent of the world’s tropical glaciers, which are more susceptible to climate change because they’re consistently near or at freezing point. Data from the US National Oceanic and Atmospheric Administration (NOAA) shows global temperatures have increased 0.06 Celsius (0.11 degrees Fahrenheit) per decade since 1850, accelerating to 0.20 C (0.36 F) per decade since 1982.

The Andes are an essential part of the region’s water cycle. The mountains store water as snow and ice during the winter, and it slowly melts during warmer months. They supply millions across the region with water, not only for drinking but also for agriculture, hydroelectricity and mining.

Glacial retreat has led to acidic rocks being exposed for the first time in centuries, leading meltwater to acidify and get contaminated with heavy metals that then leach into other water supplies in the region, which are already dwindling.

Erratic and heavy rainfall has degraded the ecosystems, making them more susceptible to erosion, landslides and severe floods.

Temperatures are rising faster at higher altitudes, with one multinational study published in the International Journal of Applied Earth Observation and Geoinformation showing that daytime winter surface temperatures in the Andes rose by 0.50 C (0.9 F) per decade since 2000 at an elevation of 1,000 to 1,500m (3,280 to 4,900ft), but by 1.7C (3.06F) above 5,000m (16,400ft).

Octavio Salazar made his first ascent of the season of Peru’s Yanapaccha mountain in early May. “It shouldn’t be raining,” he said at base camp. At this time of year, rains would normally have passed; and at an altitude of 5,000m (16,400 ft), any precipitation should be snow.

Salazar and his brother, Eloy, are Indigenous Quechua brothers who have spent decades climbing mountains in Peru’s Cordillera Blanca, the largest glacier-covered area in the tropics and home to multiple 6,000m (19,685ft) peaks, including the country’s tallest mountain.

“We feel like the climate has had such drastic changes that they often put everything you knew in doubt,” said Edson Ramirez, a park ranger and risk assessor for the Huascaran National Park, which comprises 90 percent of the Cordillera Blanca.

“Having raindrops at 5,000 metres [16,400ft] isn’t common or natural. It’s an indicator that pressure, temperature are completely altered,” Ramirez said.

Rain also means that there’s no new snowpack to replace glacier mass as it slowly moves down the mountain.

“When there’s no more glacier to cover up crevasses, it becomes a difficult maze,” Ramirez said.

“Anything humans do has some level of risk, but we’re not going to stop enjoying our mountains because of that,” said Cristian Ramirez, the head of Chile’s mountain rescue unit in Santiago.

“The Andes are the backbone of this territory,” he said. “In some way, they modulate our life because they collect ice, they collect water and we use that water to live. So mountains are life and we’re privileged to have this mountain range here.”