What’s wrong with nutrients? Aren’t they good for you? All living things need nutrients, such as nitrogen and phosphorus, to grow and survive. That’s why these nutrients are the main ingredients in agricultural fertilisers (helping crops to grow). Excess nutrients are also contained in sewage from both households and farms (excreted from all living things).

The problem arises when nutrients are dumped untreated or washed into waterways in excessive quantities: this leads to the excess growth of certain plants (algae), which consume the oxygen in the water as they grow and decay. This process, known as “eutrophication”, makes the water unliveable for fish, and the algal blooms make the waterways unpleasant for recreational use; in some cases algal blooms even become poisonous. 

This loss of biodiversity is because of the human demands placed on freshwater and wetland habitats due to such factors as: 

• Conversion of habitat, through the draining of wetlands for agriculture, urban development or damming of rivers. 

• Overuse of water for irrigation, industrial and household use, interfering with water availability; (agricultural production alone accounts for over 70 percent of water extracted from rivers – the biggest use of water worldwide). 

• Pollution of water through excess nutrients (phosphorus and nitrogen) and other pollutants such as pesticides and industrial and urban chemicals (see box: “Aren’t Nutrients Good For You?”). 

• Introduction of alien species, causing local extinction of native freshwater species. 

These threats are rapidly increasing as human populations grow and demands on water escalate.

Climate change is also becoming an important threat to wetlands and their biodiversity. Its main impacts will be on fresh water: melting glaciers and ice-caps (which are fresh water) causing rising sea levels, and changes in rainfall (less of it in some areas, leading to drought, more of it in others, leading to excessive flooding). One projection indicates that water availability will decrease in about a third of the world’s rivers. Almost half the world’s population will be living in areas of high water stress by 2030.