A third of global glaciers located at World Heritage sites will disappear by 2050, the United Nations Educational, Scientific and Cultural Organization (UNESCO) warned on Thursday.

Among the glaciers to vanish will be those at Yellowstone National Park, Yosemite National Park and Mount Kilimanjaro, according to UNESCO.

While those glaciers will melt regardless of efforts to limit temperature increases, it is possible to save the remaining two thirds of glaciers at these 50 sites, the organization stressed in a new report.

But to do so, the authors cautioned, global heating must not exceed 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, above pre-industrial levels.

“This report is a call to action,” Audrey Azoulay, UNESCO director-general, said in a statement.

“Only a rapid reduction in our CO2 emissions levels can save glaciers and the exceptional biodiversity that depends on them,” Azoulay added.

As delegates prepare to meet in Sharm El-Sheikh, Egypt, next week for COP27, the U.N. climate change conference, Azoulay stressed that the summit will play “a crucial role to help find solutions to this issue.”

“UNESCO is determined to support states in pursuing this goal,” she said.

The 1.5-degree-Celsius warming threshold is the same bar that countries said they hoped to stay below at the U.N. climate summit in Paris — COP21 — in 2015. At the time, they pledged to adhere to a 2-degree-Celsius, or 3.6-degree Fahrenheit, warming limit.  

Fifty UNESCO World Heritage sites are home to a total of 18,600 glaciers that cover an area of about 25,500 square miles, the authors found.

That’s equivalent to about 10 percent of the Earth’s total “glacierized” area, according to the report, which was compiled in collaboration with the International Union for the Conservation of Nature.

These glaciers have been retreating at an accelerated rate since the turn of the century due to carbon dioxide emissions, which are warming temperatures, the authors explained.

In total, the glaciers are losing 58 billion tons of ice each year — equivalent to the combined annual water use of Spain and France — and are responsible for about 5 percent of global sea-level rise, according to UNESCO.

Half of humanity depends either directly or indirectly on glaciers as a source of water for domestic consumption, agriculture and power, the report stressed. Glaciers are also critical to a wide range of ecosystems and the biodiversity that populates them.

In addition to the vanishing glaciers at Yellowstone, Yosemite and Kilimanjaro national parks, among those ice masses due to disappear by 2050 are those at the Waterton Glacier International Peace Park on the U.S.-Canada border.

These North American glaciers have lost 26.5 percent of their volume in the past two decades, according to the report.

Others include those at Mount Kenya, those in the Three Parallel Rivers of China’s Yunnan Protected Areas and in Western Tien-Shan — on the Kazakh-Kyrgyz-Uzbek border. These glaciers have shrunken by 57.2 percent and 27 percent, respectively, since 2000, per the report.

In Europe, glaciers in danger of disappearing include those at Mont Perdu in the French-Spanish Pyrenees, as well as those in the Dolomites in Italy, according to the report.

Glaciers at Argentina’s Los Alerces National Park and those at Peru’s Huascaran National Park are under threat in Latin America, the authors found. These glaciers have lost 45.6 percent and 15 percent of their volume, respectively, since 2000, per the report.

Glaciers in Te Waipounamu, New Zealand, meanwhile, have lost almost 20 percent of their volume since 2000, UNESCO warned.

To help save the remaining glaciers at World Heritage sites, UNESCO is calling for the creating of an international fund for monitoring and preservation.

Such a fund, the report explained, would promote related research and implementing early warning and disaster risk reduction measures.

“When glaciers melt rapidly, millions of people face water scarcity and the increased risk of natural disasters such as flooding, and millions more may be displaced by the resulting rise in sea levels,” Bruno Oberle, director-general of the International Union for Conservation of Nature, said in a statement.

Curbing greenhouse gas emissions and investing in nature-based solutions “can help mitigate climate change and allow people to better adapt to its impacts,” Oberle added.