A new study published in the prestigious science research journal Nature has further confirmed that climate change can lead communities to water scarcity by putting the world’s most needed water towers at risk.

These natural water towers within mountains supply water to 1.9 billion people — a quarter of the world’s population. But as mountain ecosystems break down from climate change, these water sources are becoming increasingly vulnerable.

Without immediate action, almost 1.9 billion people will face water scarcity. And the deterioration of these water towers threatens half of the world’s biodiversity. So let’s take an in-depth look into the how, why, and what must be done.

Human Dependence on Water Towers

Although often unconsidered, water towers play an essential role in the global water cycle. Prevalent in mountainous ecosystems, they store large amounts of water in snow and glaciers, which delays run-off.

Because of this buffering time, water towers act as constant, dependable sources of water during warmer months. As water melts, it trickles downstream and hydrates those living at lower altitudes. The study examined 78 of the world’s water towers, which can span across multiple mountain ranges.

These water towers are the main water supply source for mountain ecosystems. And although only 250 million people live in areas with water tower units, another 1.6 billion depend on them from downstream. This adds up to about 22% of the global population — almost a quarter of the world.

Water Scarcity Also Threatens Biodiversity

Not only that, but water towers support 50% of the world’s biodiversity hot spots, since so many exists in mountainous ecosystems. One third of the world’s terrestrial species diversity makes a home in mountainous ecosystems, as well. Plant diversity in particular thrives in mountains.

Even beyond the ecological benefits of mountains, they offer incredible cultural and economic significance. According to the study, anywhere from 4 to 18% of the world’s GDP is dependent on water towers. They attract a large tourism industries, house important cultural and religious landmarks, and generate important natural resources.

But rising temperatures have disrupted the rate at which water towers and their glaciers melt, jeopardizing the reliability of these water sources. As this problem grows over time, the threat of water scarcity for almost 2 billion people will too.

New Risks of Water Scarcity

Of the world’s water towers, the Indus is both the most important and most vulnerable. Collecting water from the Himalayan, Hindu Kush, Ladakh, and Karakoram mountain range, it provides water for 206 million people in Afghanistan, China, India, and Pakistan.

But the Indus is in grave trouble. The study’s authors fear that the water tower may not make it to even 2050. This problem will only worsen, considering the growing demands for water in this region.

The population is expected to grow by 50% in the coming decades and produce eight times as much GDP. With the water tower under additional threat from rising temperatures and less steady rainfall, the very future of this region is uncertain. For the Indus, water scarcity is imminent.

Even beyond the Indus, threats to water towers everywhere will bring grave consequences.

“We always knew the Indus was important, but it was surprising how the Rhône and Rhine have risen in importance, along with the Fraser and Columbia,” said study co-author Dr. Bethan Davies.

Global Warming Exacerbates Risks

She goes on to warn that global rises in temperature will only exacerbate the issue. If we confine global warming within 1.5C, only around 25% of mountainous snow and ice would disappear in the coming decades.

But tampering global warming to 1.5C would require serious upheaval of global environmental policy. Without that change, 80% of the water stored in the world’s water towers would — almost literally — evaporate by 2100. With such a high percentage, we can only imagine the consequences.

Fighting the “Downstream Battle” Against Water Scarcity

To combat the growing concerns for the future for water towers, the study suggests a few steps.

Specifically, the authors urge the international community to recognize the importance and vulnerability of the world’s water towers, which is “driven both by socioeconomic factors and climate change.”

They also recommend the development of “mountain-specific conservation and climate change adaptation policies,” such as more national parks, control on pollutants and erosion, and regulations for dams and emissions.

Continued activism for steady access to clean water will also help, as will creating a more sustainable water purification industry.

Simply put, ensuring that water towers continue to send water downstream will be an uphill battle, but one that must be fought nonetheless.