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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

  • One fifth of the world’s river basins are experiencing rapid changes in the area covered by surface waters, which indicates a growth in flooding, new reservoirs, and the drying up of water bodies. (UN-Water 2021)
     
  • 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 area covered by coastal mangroves has declined globally by 4.2% since 1996. (UN-Water 2021)
     
  • Wetlands are being drained for agriculture, with some 87% lost globally in the last 300 years, and more than 50% since 1900. (UNEP)
     
  • Water pollution has worsened since the 1990s in almost all rivers in Latin America, Africa and Asia, with severe pathogen pollution affecting around one third of all river stretches in these regions. (UNEP, 2016)
     
  • Ecosystems across the world, particularly wetlands, are in decline in terms of the services they provide. Between US$4.3 and US$20.2 trillion per year worth of ecosystem services were lost between 1997 and 2011 due to land use change.  (Costanza et al. 2014)
     
  • Ecosystem valuation has demonstrated that benefits far exceed costs of water-related investments in ecosystem conservation. The 2011 economic value of ecosystem services has been globally estimated at US$124.8 trillion. Global GDP was estimated at US$75.2 trillion in the same year. (Costanza et al. 2014)
     
  • Globally, the number of lakes with harmful algal blooms will increase by at least 20% until 2050. (UN DESA, 2012)
     
  • An estimated 20% of the world’s aquifers are being over-exploited leading to serious consequences such as land subsidence and saltwater intrusion. (Gleeson et al. 2012)
     
  • 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)
     
  • Naturally occurring arsenic pollution in groundwater now affects nearly 140 million people in 70 countries on all continents. (WHO, 2018)