As the planet warms, Earth’s ice masses are vanishing at an alarming rate. This rapid thaw is not only raising sea levels but also reactivating ancient and modern microorganisms, some of which could alter ecosystems and intensify the threat of antimicrobial resistance (AMR), a new United Nations report warned.
The Frontiers 2025: The Weight of Time report released by the UN Environment Programme (UNEP) on July 10, 2025 warned that the cryosphere — the planet’s frozen regions — is at the frontline of climate change. The impacts of a 2 degrees Celsius (°C) rise in global temperatures would include irreversible sea-level rise and the dramatic loss of glaciers, sea ice and permafrost, the report states.
The cryosphere includes the Antarctic and Greenland ice sheets, ice shelves, mountain glaciers on every continent, permafrost and seasonally frozen ground. It covers 52 per cent of the Earth’s land surface and 5 per cent of ocean area, making it one of the most affected zones among terrestrial and aquatic ecosystems. It directly supports 670 million people and billions more who depend on freshwater from these frozen reserves.
According to UNEP, Arctic sea ice is shrinking so rapidly that the Arctic Ocean may become seasonally ice-free before 2050. Even if warming is limited to 1.5°C, projections show world’s glaciers could be halved by the end of the century. Between 24 per cent and 69 per cent of near-surface permafrost could thaw by the end of the century, the UNEP report said.
Such thawing risks reawakening dormant viruses, bacteria and fungi, some potentially tens of thousands of years old. While some cryospheric microorganisms may not survive thawing, many others are likely to interact with present-day microbes and multicellular organisms, potentially infecting plants, animals and humans.
According to the UNEP report, specific populations of re-emerging micro-organisms could thrive in these new environments, profoundly altering the structure and function of existing microbial communities and surrounding ecosystems.
One cited example is the anthrax outbreak in Russia’s Yamal Peninsula in 2016. Exceptionally high summer temperatures caused permafrost to thaw, reactivating Bacillus anthracis spores long frozen in the soil. The outbreak killed over 2,000 reindeer and infected about 90 herders.
Another consequence of opening this Pandora’s box is the rise of antimicrobial resistance genes, driven by changes in cryospheric microbial communities.
The report also warned that the acquisition of virulence-related genes by bacteria may give rise to more potent pathogens, capable of causing disease more efficiently. Researchers recently detected thousands of virulence factors in microorganisms recovered from 21 Tibetan glaciers.
In addition, scientists have documented a variety of bacteria and fungi preserved in ice cores across regions including Greenland, Denmark, Ellesmere Island (Canada), South America, the Qinghai-Tibetan Plateau, Alaska, the Himalayas, Siberia and Antarctica.
In 2023, some researchers revived a female roundworm — a previously unknown species — that had been dormant in Siberian permafrost for nearly 46,000 years. Remarkably, the organism resumed life and began reproducing asexually.
Another threat emerging from the thawing cryosphere is the release of antimicrobial resistance (AMR) genes.
Myriads of antimicrobial resistance genes, conferring resistance against modern-day antibiotics such as chloramphenicol, beta-lactams, streptomycin and tetracycline, have been detected in cryospheric ecosystems.UNEP Frontier report
Some cryospheric microorganisms, known as psychrophiles — species that thrive at near-freezing temperatures — have evolved a range of strategies to survive harsh conditions. These include the production of antifreeze proteins, compounds that aid membrane fluidity and pigments that act as natural sunscreen. Many are also capable of long-term dormancy.
Psychrophiles also produce cold-active enzymes that function at low temperatures and these have found commercial applications in the food and beverage industry, pharmaceuticals, detergents and biotechnology.
Despite these adaptations, scientists emphasise that global cryosphere loss is potentially irreversible if greenhouse gas emissions continue unchecked. Even if emissions were halted immediately, the report warned, it could take centuries for the cryosphere to return to mid-20th century conditions.
To reduce further loss, the report urges an urgent crackdown on short-lived climate pollutants — particularly black carbon — that accelerate glacier melt. These dark particles reduce the reflectivity (albedo) of ice surfaces, causing them to absorb more heat.
Primary sources of black carbon include emissions from diesel engines, open-field crop burning and wildfires. Tackling these at the source is essential, the report said.
Other recommendations include regulating tourism in fragile cryospheric areas and deploying reflective geotextile sheets over glacier surfaces to reduce seasonal melt. However, the report notes that scaling up such methods, currently used on ski slopes, to cover entire glaciers would be prohibitively expensive and could introduce plastic pollution through material degradation.
UNEP concluded the report by warning that rapidly melting glaciers and thawing permafrost are stark indicators of the world’s failure to adequately mitigate greenhouse gas emissions over the past three decades — a failure with increasingly ominous consequences.
“By failing to avoid the unmanageable, we now must manage the unavoidable, witnessing the loss of stable ecological systems that our species evolved with and struggling to preserve samples of those systems’ diversity and unimaginable value,” it said.