Sharply reduce water pollution and improve water quality

Water pollution is degrading freshwater ecosystems

Water pollution is a growing threat to clean water, which is fundamental to life on Earth and sustains both ecological integrity and human well-being. Lakes, rivers, wetlands, aquifers and other freshwater ecosystems store, filter and replenish much of the planet’s usable freshwater, forming deeply interconnected systems.

Water — free of pollutants and contaminants — is also essential for freshwater ecosystems. Despite covering only 1% of the Earth’s surface area, these ecosystems support around 10% of all known species and 33% of vertebrate species. Yet water quality is declining globally, directly harming freshwater species, degrading ecological functions and the delivery of ecosystem services, and reducing access to safe water for people.

Declining freshwater quality has been driven by increasing water pollution and contamination from a variety of sources. Globally, 80% of wastewater is inadequately treated or completely untreated. As contaminants and pollutants enter and accumulate in freshwater ecosystems, they interact with food webs and species in varied and complex ways, many of which researchers are still trying to understand. However, pollutants are known to negatively impact the physiology and behavior, and in turn survival, of many freshwater species and the functions and services of freshwater ecosystems.

Furthermore, the excessive use and runoff of agricultural fertilizers rich in nitrogen and phosphorus — a major source of water pollution — can intensify natural nutrient-cycling processes in freshwater ecosystems. This is a primary driver of eutrophication, a process that depletes dissolved oxygen and creates low- or no-oxygen (i.e., hypoxic) “dead zones” in the water column. These conditions can produce harmful algal blooms and the subsequent release of toxins from cyanobacteria into the water supply, harming people and biodiversity alike.

Water contamination and water quality is intrinsically linked with human health. Contamination by persistent organic pollutants such as agricultural pesticides and industrial chemicals like per- and polyfluoroalkyl substances (PFAS); contaminants of emerging concern (emerging contaminants), including pharmaceuticals, microplastics and antimicrobial-resistant microorganisms; and heavy metals pose significant risks. These pollutants are associated with a range of direct and indirect health impacts, such as compromised immune systems and increased incidences of chronic diseases — including cancer — in affected populations.
 

Reducing water pollution and improving water quality requires coordinated implementation

Addressing these interconnected crises requires a holistic approach: targeting the behavioral drivers of pollution, accounting for the bioaccumulative nature of some contaminants, reducing primary pollutant discharge and enhancing circularity within water management systems. Targets aimed at addressing some or all of these drivers of declining freshwater quality are highlighted in key international frameworks — including the U.N. Sustainable Development Goals, the Kunming-Montreal Global Biodiversity Framework, the Stockholm Convention on Persistent Organic Pollutants and the Convention on the Protection and Use of Transboundary Watercourses and International Lakes (known as the Water Convention), as well as leading scientific literature.

While the challenges facing freshwater ecosystems vary significantly between countries, regions and basins, some broad shifts in improving water quality and reducing water pollution can help deliver the changes required to meet high-level goals and reduce pollution to conserve biodiversity. Increasing awareness and understanding of the ways humanity is degrading water quality — and the consequences of those actions — are critical to ensuring that freshwater ecosystems and their services can be appropriately recognized and protected.

We already know many of the solutions for safeguarding freshwater quality — for example, improving regulations and enforcement, using sustainable practices, removing harmful subsidies, improving wastewater treatment and appropriately valuing freshwater ecosystem services. Additionally, because of the interconnected nature of hydrological systems, transboundary cooperation and collective stewardship of water resources are essential for addressing transboundary drivers of declining water quality.

While solutions are known, they now require coordinated implementation at scale, across sectors and borders, to safeguard freshwater ecosystems for generations to come.