In the land where the legend of El Dorado began, the race is on to solve the mystery of a vital 21st-century treasure – the water that tens of millions of people rely upon across northern South America. “It’s blue gold, and we are looking for it,” says Mauricio Diazgranados, a Colombian botanist.

The misty and marshy páramo landscapes that sit above the tree line and below the snow caps of the soaring Andes peaks are known as the living factories that ensure a steady flow of clean water to the region’s growing population.

But after many centuries of protection as sacred places, the páramos face a battery of threats: destruction by farming and mining, rapidly rising temperatures and a triple plague attacking the exotic frailejones plants that stand like silent armies defending the land.

Facebook Twitter Pinterest Colombian botanist Mauricio Diazgranados. Photograph: Damian Carrington/The Guardian

Healthy páramos are covered with plants adapted to the extreme conditions in the high-altitude tropics, where scorching sun is followed by freezing nights. They are highly efficient at capturing huge quantities of water from the thick rolling fogs and rains, then trapping it in rich peat soils and slowly releasing it, preventing floods in the wet season and drought in the dry months. This steady supply provides virtually all the water for big cities such as Bogotá and Quito in Ecuador, where water shortages strike regularly.

“It really is a sponge!” says Diazgranados, from Kew Gardens in west London, picking up a fistful of moss in the Paramo de la Rusia in northern Colombia. It’s the end of the dry season but water still drips out as he squeezes.

Despite the critical importance of the páramos, until recently it was one of the least known ecosystems in the world. Now a team of researchers have set out to give the paramos the most thorough and hi-tech examination yet, from above, on and below the ground, aiming to reveal exactly how the giant water towers work and can be protected.

The stakes could not be higher, says Juan Pablo Romero, from the Nature Conservancy in Bogotá, and not part of the team. “If you don’t have water, you don’t have anything. We won’t be able to function as a society.”

Steady water flow is also crucial for hydropower, which dominates the electricity supply of the region. The new research may have global importance too, as there are similar landscapes in Africa, south-east Asia and Hawaii.

In the Páramo de la Rusia, the sharp peaks rise to 4,000 metres, eagles soar over deep green valleys, and mountain lions and wild guinea pigs roam the slopes. When the sun breaks through the mists, the crowns of the frailejones light up in silvery green, like lanterns across the mountainside. Their shininess is a vital protection from the sun’s intense UV radiation.

Facebook Twitter Pinterest The páramos in the high Andes. The region is also being examined from space. Photograph: Courtesy of Mauricio Diazgranados

As an eagle passes, Charles George, a researcher at the Centre for Ecology and Hydrology (CEH) in the UK, cries: “OK, everyone, I’m flying.” His warning is for the drone that takes to the air and begins its passes, photographing the landscape and plants in 3D detail. “The important thing here is not to fly into the mountain!”

The páramos are also being examined from space. It is one of the first places where a new satellite radar method is being used to track the rise and fall of the plant-covered land to within a millimetre. “It’s giving an entirely new view of the peat,” says David Large, a senior research fellow at the University of Nottingham.

Where peat is being degraded, the ground level will fall; where it is accumulating, as it should in a natural system, the land rises. “It’s like a heartbeat. If you get a good rhythm out of the bog, that’s like a good heartbeat. If not, it’s like an arrhythmia.”

On the ground, Diazgranados is sizing up the frailejones, which can grow to 10 metres over centuries and exist only in the páramos. “That’s beetle poop,” he says, pointing at dark flecks deep inside the fleecy crowns. Over the past decade, a triple plague has attacked the plants: beetle larvae, a night moth and a deadly fungus.

The cause is unknown, as some of the pests are new to science, but climate change is the key suspect, allowing lower-altitude species to invade as temperatures rise. The frailejones may be a crucial component of the páramos water factory, so the team are making 3D measurements of thousands of plants to measure their storage capacity.

Facebook Twitter Pinterest The frailejones, or big monk. The páramos is the most biodiverse mountain ecosystem in the world. Photograph: Courtesy of Mauricio Diazgranados

The páramos investigation is also going underground. In a neighbouring valley, where cattle raising and potato growing is more intense, Ed Rowe, the team’s soil ecologist and from CEH, is up to his waist in a pit he has dug in a field converted into pasture by burning.

“This would have been fluffy and held lots of water before. It would have been up to here,” he says, holding his arm about 50cm above ground level. Rowe thinks it has lost about half its water storage capacity, compacted by the hooves of cows and shrunk as exposed peat decays into carbon dioxide. He is taking samples to date the carbon and see where the oldest peat is being washed away.

Some parts of the páramos have already come back from the dead. “Fifty years ago, this land was bare like skulls: you could only see the rocks,” says a local farmer, José Álvaro, waving his arm across a recovered páramo that was once repeatedly burned. Álvaro, 81, remembers a massive fire sweeping through this valley in 1955, deliberately set but which got out of control.

Facebook Twitter Pinterest Local farmer José Álvaro, 81, on a hillside. Photograph: Damian Carrington/The Guardian

“The old people had to find a path in life and needed the land for cows, sheep and goats,” he says. “But if the old people have destroyed, the young people will have to restore, but it will take a very long time.”

For many centuries, the páramos where protected by indigenous people as sacred places where the gods lived. The legend of El Dorado began in the páramos, where leaders or shamans would cover themselves in gold dust and dive into paramos lakes, throwing golden offerings for the gods. Spanish conquistadors searched for these treasures but called the paramos the Empire of Darkness, and many perished in the cold and boggy lands.

More recent protection was inadvertently provided by Colombian guerrillas, including the Farc, whose commander, Romaña, captured Diazgranados in the Sumapaz páramos near Bogotá in the mid-1990s. The party escaped in a nighttime march through the mountains.

But the páramos, the most biodiverse mountain ecosystem in the world, are now in mortal danger and no one knows how much has been lost already. Gold is again a factor, via both legal and illegal mining, along with coal and iron ore extraction. Global warming heats up mountains even faster than the lowlands, and it is predicted that half the remaining páramos could be destroyed by 2050.

Colombian court bans oil, gas and mining operations in paramos Read more

German Grimaldos, 57, who has always lived by the Páramo de la Rusia, is clear: “The biggest threat we have is global warming. It heats the soil very fast.”

Fields cut into the páramos have hit water supplies to the nearby town of Belen, where Grimaldos lives. “Both the quantity and quality has got worse. When it rains, it washes all the soil, chemicals and fertiliser down to the town.” The cutting down of many thousands of frailejones to make traditional houses has also been harmful, he says. The practice only ceased in 2007.

France Gerard, at CEH and leader of the £1.3m project examining the páramos, says listening to the stories of local people is crucial. “They have been living in this place a long time and they will have an idea of how a páramo works. We’re convinced they can teach us something. Local farmers may, for example, have learned the most crucial areas to protect.”

Facebook Twitter Pinterest The UK’s Centre for Ecology and Hydrology team on the ground in Colombia. Photograph: Courtesy of France Gerard

Gerard’s team will present their understanding of how the páramos work back to the local people at the end of the three year project, and the prospect of making a difference to many people’s lives is a big driver. “It makes me quite emotional,” she says. “We only have one Earth and the more we find out about it, the better we can protect it.”

The project is funded by the UK government, in parallel with Colombian government projects, and could have a wider significance if it cracks the mystery of exactly how water is regulated at high altitudes.

“It is a global problem because half of the world’s population depend on mountains” says Boris Ochoa Tocachi, an Ecuadorean hydrologist on the team. “Impacts on those mountains will clearly impact people, especially their clean and clear water.”

Sitting on the mountainside he has known for eight decades, Alvaro emphasises the sheer beauty of the páramos. “I am very proud to live here, and very happy. It is a beautiful land.”

He then sings a few lines from an old song, ending: “I love my land as I love my mother.”

The extraordinary ‘big monks’ of the páramos Facebook Twitter Pinterest The Kew team shelter from the sun. Photograph: Courtesy of Mauricio Diazgranados

In the dense mist that frequently drapes the páramos, it can seem like thousands of silent figures are watching. But they are plants, whose human scale and the distinctive leaves that crown them, gave them their popular name – frailejones, or big monks.

The striking plants, which can live for centuries, are found only in the northern Andes and through evolution have solved how to thrive in the extreme high-altitude environment.

“The sun is so strong it would burn the plants, so they have to protect themselves,” says Diazgranados. Their leaves are covered in tiny silvery hairs that reflect the light and make them gleam like beacons on the mountainside.

But sunscreen is not the only thing needed to survive. The soft hair also insulates the plant against the freezing alpine temperatures at night. Furthermore, most plants evaporate water from their leaves to draw up water and nutrients through their roots. But at night it is too cold for this, while opening their stomata in the glare of the sun would cause them to shrivel.

So they have become incredibly thrifty water users, passing up to 90% of the water they catch in their rosettes straight into streams. Pines, for example, pass on just 20%, evaporating the rest.

Facebook Twitter Pinterest Frailejones make a thriving micro-ecosystem. One such plant in Venezuela contained 130,000 insects and spiders. Photograph: Damian Carrington/The Guardian

This superpower of the frailejones may be a significant part of the reason why the páramos have been such reliable water towers for millions of people. They are also vital for other life on the high mountains.

As they grow, the dead leaves pile up in neat layers under the growing crown and make a thriving micro-ecosystem for frogs, insects and spiders. One plant in Venezuela was found to harbour 130,000 insects and spiders. “They are a keystone species,” says Dizagranados.

There are 143 known species of frailejones, of which Colombia hosts 88. Most are under threat of extinction from farming, mining and agricultural expansion. Diazgranados has himself discovered 13 new species and he is sure more await discovery.

This is because each high peak is an isolated “sky island”, meaning unexplored mountains will have their own species that evolved in isolation. Elsewhere in the world, other plants have independently evolved the same solutions to high-altitude living, such as the silver sword in Hawaii.