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Global Biodiversity Outlook 3

Inland water ecosystems

Current path:

Inland water ecosystems continue to be subjected to massive changes as a result of multiple pressures, and biodiversity to be lost more rapidly than in other types of ecosystem. Challenges related to water availability and quality multiply globally, with increasing water demands exacerbated by a combination of climate change, the introduction of alien species, pollution and dam construction, putting further pressure on freshwater biodiversity and the services it provides. Dams, weirs, reservoirs for water supply and diversion for irrigation and industrial purposes increasingly create physical barriers blocking fish movements and migrations, endangering or extinguishing many freshwater species. Fish species unique to a single basin become especially vulnerable to climate change. One projection suggests fewer fish species in around 15% of rivers by 2100, from climate change and increased water withdrawals alone. River basins in developing countries face the introduction of a growing number of non-native organisms as a direct result of economic activity, increasing the risk of biodiversity loss from invasive species.

Impacts for people:

The overall projected degradation of inland waters and the services they provide casts uncertainty over the prospects for food production from freshwater ecosystems. This is important, because approximately 10% of wild harvested fish are caught from inland waters, and frequently make up large fractions of dietary protein for riverside or lake communities.

Alternative paths:

There is large potential to minimize impacts on water quality and reducing the risk of eutrophication, through investment in sewage treatment, wetland protection and restoration, and control of agricultural run-off, particularly in the developing world.

There are also widespread opportunities to improve the efficiency of water use, especially in agriculture and industry. This will help to minimize the tradeoffs between increasing demand for fresh water and protection of the many services provided by healthy freshwater ecosystems.

More integrated management of freshwater ecosystems will help reduce negative impacts from competing pressures. Restoration of disrupted processes such as reconnecting floodplains, managing dams to mimic natural flows and re-opening access to fish habitats blocked by dams, can help to reverse degradation. Payments for ecosystem services, such as the protection of upstream watersheds through conservation of riparian forests, can reward communities that ensure continued provision of those services to users of inland water resources in different parts of a basin.

Spatial planning and protected area networks can be adapted more specifically to the needs of freshwater systems, by safeguarding the essential processes in rivers and wetlands, and their interactions with terrestrial and marine ecosystems. Protection of rivers that are still unfragmented can be seen as a priority in the conservation of inland water biodiversity. Maintaining connectivity within river basins will be increasingly important, so that species are better able to migrate in response to climate change.

Even with the most aggressive measures to mitigate climate change, significant changes to snow and glacier melt regimes are inevitable, and are already being observed. However, the impacts on biodiversity can be reduced by minimizing other stresses such as pollution, habitat loss and water abstraction, as this will increase the capacity of aquatic species and ecosystems to adapt to changes in snow and glacier melting.

  • United Nations
  • United Nations Environment Programme