Water and Ecosystems
Life on Earth depends on healthy ecosystems. Freshwater ecosystems, such as wetlands, rivers, mangroves and aquifers, are a critical part of the global water cycle – supplying, purifying and protecting freshwater resources.
Mismanagement combined with climate change is devastating many ecosystems, undermining their ability to provide freshwater ‘services’, which threatens the health of human societies and natural environments.
The issue explained
Ecosystems supply, purify and protect freshwater resources. Apart from directly captured rainwater, humans get every drop of freshwater via three types of ecosystem: groundwater, surface water, and frozen water.
Freshwater ecosystems mitigate the effects of floods and drought. Ecosystems such as coastal mangroves and river bank vegetation protect the land from erosion and inundation; wetlands and glaciers regulate water flows; and, aquifers can act as a storage buffer during dry spells.
Biodiversity in freshwater ecosystems is in danger. Freshwater species are going extinct more rapidly than terrestrial or marine species. Habitat loss and pollution are a growing threat.
Human impact on ecosystems is affecting water quantity and quality. Natural landscapes are being lost to urbanization, industry and agriculture. Climate change exacerbates the effect on water.
Surface water area is changing fast. In some areas, flooding and increased rainfall are increasing surface water area. In other areas, lakes, wetlands and floodplains are drying up due to reduced precipitation and/or unsustainable management.
Lake water high turbidity is a growing issue. High turbidity is where water appears ‘cloudy’. The suspended particles act as magnets for pollutants and bacteria, affecting human and ecosystem health, and damaging tourism.
The way forward
Freshwater ecosystems must be protected and losses reversed. Governments are being urged to implement and enforce policies and laws at the national and river basin level to sustainably manage freshwater ecosystems, balancing the needs of communities, businesses, and the environment.
Nature-based solutions to climate change are essential. Protecting, restoring, enhancing, and in some cases creating freshwater ecosystems and natural features, such as wetlands and river bank vegetation, can protect lives and livelihoods against extreme weather events.
‘Ecosystem services’ can contribute to wastewater treatment. Wetlands can act as an alternative or supplement to conventional water treatment systems, filtering and purifying wastewater before it enters rivers or lakes.
Wastewater can help rejuvenate ecosystems. The extraction and safe reuse of the water, nutrients and organic matter in wastewater from sanitation systems can be used to enhance ecosystems services in a more circular economy.
Data is key. To guide interventions to where need is greatest, and to help all water users improve their sustainable management of water, the amount and quality of data on freshwater ecosystems needs to increase.
Coordination across sectors and borders is vital. Freshwater ecosystems serve every type of human activity, support all life on Earth, and cross national boundaries. Effective coordination to protect and restore these ecosystems means integrating plans across sectors and between governments.
Facts and Figures
Peatlands are unique and rare wetland ecosystems that, despite only covering around 3-4% of the planet’s land surface, contain up to one-third of the world’s soil carbon – twice the amount of carbon found in the world’s forests. (UNEP, 2024)
Glaciers store approximately 70% of the world’s fresh water, making them the largest reservoir of fresh water on Earth. (WMO, 2024)
Wetlands such as mangroves, seagrasses, marshes and swamps are highly effective carbon sinks that absorb and store CO2, helping to reduce greenhouse gas emissions. (UNEP, 2021)
More than 90 out of 185 countries have one or more water-related ecosystem in a state of degradation. (UN-Water, 2024)
River flow has significantly decreased in 402 river basins worldwide, where approximately 107.5 million people live. This is a fivefold increase from 15 years ago. (UN-Water, 2024)
Surface water bodies, such as lakes, are shrinking or being lost entirely in 364 (of 13,894) basins worldwide, where approximately 93.1 million people live. (UN-Water, 2024)
Exceptionally high temperatures and dry conditions impacted wildlife In Latin America and the Caribbean in 2023. In Tefé Lake, in the Brazilian Amazon, the water temperature reached a record high and over 150 river dolphins were reported dead. (WMO, 2024)
21 million people, including 5 million children, live within 5 km of lakes with high turbidity (water cloudiness), which can indicate water pollution. (UN-Water, 2021)
The world has lost 5,250 km2 of its mangroves, a net decrease of 3-4% since 1996. (UN-Water, 2024)
Wetlands are being drained for agriculture, with some 85% lost globally in the last 300 years, and more than 50% since 1900. (UNEP, 2022)
Sea-level rise is projected to extend salinization of groundwater, decreasing freshwater availability for humans and ecosystems in coastal areas. (IPCC, 2008)
- Soil erosion from croplands carries away 25–40 billion tonnes of topsoil every year, significantly reducing crop yields and the soil’s ability to regulate water, carbon and nutrients, and transporting 23–42 million tonnes of nitrogen and 15–26 million tonnes of phosphorus off land, with major negative effects on water quality. (FAO/ITPS, 2015)