UN Warns of 4 Climate Threats: Microbes, Pollution, Ageing

A man gives his grandson a drink of water amid a drought in Kenya. (file)

In a world increasingly shaped by climate extremes, environmental experts are issuing a stark warning: four rapidly emerging threats could reshape life for millions unless urgent action is taken.

From ancient microbes awakening in melting glaciers to toxic pollutants released by floods, the dangers are no longer distant or theoretical—they are real, and they are growing.

The Frontiers Report 2025, released by the UN Environment Programme (UNEP), highlights four critical areas where environmental degradation intersects with human vulnerability: legacy pollution, melting glacier microbes, undamming rivers, and climate risks for an ageing population.

The report paints a vivid picture of how climate change is not only altering ecosystems but also exposing communities—especially the most vulnerable—to new and intensifying dangers. Some issues may be local or relatively small-scale today but could become regional or global concerns if not addressed early, the report warns.

UNEP Executive Director Inger Andersen urged immediate action “to protect people, nature and economies from threats that will only grow with each passing year.”

1. Melting Glacier Microbes

Climate scientists warn that many glaciers may not survive this century unless steps are taken to slow the melting caused by climate change. This poses a dual threat for downstream populations: increased flooding and the possible release of ancient microbes from the melting ice.

Frozen in ice sheets, glaciers, and permafrost are bacteria, fungi, and viruses. While many are dead, some are dormant—and some remain active. As global temperatures hit record highs, these microorganisms could become active in modern ecosystems.

Even if melting slows due to emissions reductions, experts stress the importance of assessing and preparing for the potential threats from these microbes. Documenting and preserving cryospheric microorganisms could also reveal insights into climate history, aid disease treatment, and support new biotechnologies.

2. Dismantling Dams

In the Colombian Amazon, river levels have dropped by up to 80%, restricting access to drinking water and food, closing 130 schools, and increasing the risk of child exploitation by non-state armed groups. This has led to a spike in respiratory infections, diarrhoeal diseases, malaria, and acute malnutrition in children under five.

Dams are compounding the effects of climate-induced drought in Colombia and beyond. According to UNICEF, over 420,000 children in Brazil, Colombia, and Peru are currently out of school due to water shortages.

Removing dams and other barriers is increasingly seen as vital to rehabilitate river ecosystems. These efforts, often led by local communities, Indigenous Peoples, women, and youth, have shown that rivers can recover rapidly—but only if pollution and climate stressors are addressed simultaneously. Understanding the impact of dam removal is key to guiding future decisions on river restoration.

3. Climate Risks for the Elderly

Older populations face greater risks during extreme weather events and suffer more from environmental degradation. As the World Meteorological Organization (WMO) predicts more frequent heatwaves, data shows elderly people are suffering disproportionately—evident in rising deaths and illnesses during recent hot spells.

The world’s ageing population is expanding rapidly. By 2050, the share of people over 65 will rise from 10% in 2024 to 16%, with most living in cities where extreme heat, air pollution, and disaster risks are more severe.

Protecting the elderly requires evolving and effective adaptation strategies.

4. Legacy Pollutants

Flooding events are increasing worldwide. Hidden among their impacts are legacy pollutants—hazardous substances long buried in sediments that are released when floodwaters stir them up.

Examples include the 2010 Pakistan floods, 2012 Niger Delta flooding, and 2017’s Hurricane Harvey in Texas, where heavy metals and persistent organic pollutants were released into the environment.

To tackle this threat, UNEP calls for sediment assessments, nature-based flood protection strategies, and investment in natural remediation of contaminated sites.