Earth Today | Thawing threat

AS THE world’s frozen regions thaw due to global warming, a new report has flagged the likely reactivation and remobilisation of both modern and ancient micro-organisms that can be harmful to health.

According to the new Frontiers report of the United Nations Environment Programme (UNEP), between 1994 and 2017, some 28 trillion tonnes of ice vanished from the Earth’s cryosphere and, compared to the 1990s, the overall rate of ice loss increased by 57 per cent over those 24 years.

“Projections to 2100 suggest that the number of the world’s glaciers will be halved, even if temperature increase could be limited to 1.5 degrees Celsius. Glaciers are no longer shrinking – they are disappearing. Similarly, recent estimates suggest that 24 to 69 per cent of the planet’s near surface permafrost will thaw by 2100,” explained the 2025 report titled ‘The weight of time: Facing a new age of challenges for people and ecosystems’.

The potential consequences are eyebrow raising.

“Cryosphere warming will reactivate and remobilise modern and ancient microorganisms to new terrestrial and aquatic environments. Once there, specific populations of re-emerging microorganisms might thrive, profoundly modifying the structure and function of the existing microbial communities and surrounding ecosystems,” the report warned.

“Many of these newly released microorganisms will interact with present-day microbial communities and with multicellular organisms. Research suggests that some reactivated microbes could be pathogens, able to infect plants and animals, including humans.The possibility of widespread outbreaks is unlikely, but scientists are honing their abilities to assess the threat presented by the release of these ancient pathogens from their frozen state,” it added.

The report also referenced real-life examples of what is possible with thawing.

“For instance, coliform bacteria from Canadian Arctic ice samples of up to 2,000 years of age were isolated in a research facility in the 1990s. In 2015, researchers reactivated strains of Bacillus anthracis from three separate layers of sediments deposited since 1300s in Siberia’s far northeast Yakutia region,” it said.

“In July 2016, an Anthrax outbreak in the northwestern Yamal region of the Russian Federation’s killed over 2,000 reindeer herds and led to the hospitalization of 90 people from herder communities.85 Researchers theorized that the abnormally high temperatures in that summer and the permafrost thaw contributed to the reactivation of B. anthracis in soil reservoirs, among other factors,” it added.

And pathogen reactivation, the UNEP report noted, is not restricted to bacteria.

“Fungi, either filamentous or unicellular (yeasts), have also been isolated from cryospheric habitats, including some with known pathogenic potential.Also, research published in early 2023 reports a controlled experiment reactivating 13 new viruses isolated from seven different Siberian permafrost samples and successfully infecting Acanthamoeba hosts. The experiment was designed to demonstrate that viruses can reactivate from a frozen state and infect a pervasive protozoan commonly found in soil, air, and water samples worldwide,” it said.

“While we should remain vigilant for viable pathogens, another facet of the warming cryosphere raises concerns: virulence-related and antibiotic resistance genes moving between microbes.The transfer of genetic material from one cell to another, called horizontal gene transfer, only exists in the microbial world, where it occurs frequently and indiscriminately among species in natural ecosystems,” it said.

“Acquisition of the virulence-related genes by bacteria can give rise to strains with enhanced powers as a pathogen that are more efficient in causing disease. Researchers recently detected thousands of virulence factors in microorganisms collected from 21 Tibetan glaciers,” the report added.

There also exists the risk of destroyed carbon sinks, which are natural or artificial systems that absorb more carbon dioxide than they release.

“The most pertinent consequence of reactivated microbes from cryospheric habitats is the decomposition of organic matter in thawing soil, transforming a carbon sink into a carbon source,” it said.

Climate change is fuelled by the warming of the planet, caused by the human consumption of greenhouse gases including carbon dioxide, among others. Essential to the global response to mitigate climate change are, therefore, efforts to reduce greenhouse gas emissions and to preserve carbon sinks, which also include forests, fungi, and soil.

“Permafrost soils in the northernmost region store the largest volumes of organic carbon in the form of peat layers, readily available for microbial decomposition. Increased microbial activities enhanced by permafrost thaw release vast amounts of carbon dioxide, methane and nitrous oxide, three well-known greenhouse gases, to the atmosphere,” the report noted.

“At the same time, microbes exist that consume these gases. The interactions and composition of these GHG-producing and -consuming microbes, together with changing environmental conditions, play a critical role in determining the permafrost carbon feedback to climate,” it added.

pwr.gleaner@gmail.com