Nutrient overload remains despite improvements in legislation

In recent years, strict legislation was introduced to control the amount of nitrate and phosphate that runs into the sea from European rivers.  However, water quality has not improved as much as expected and researchers estimate that a time lag of up to 40 years may need to be considered.

  • Excess nutrients can cause an unnatural algae ‘bloom’, stripping oxygen from water and reducing populations of fish and other animals. Controlling discharge of nutrients from human sources, including agricultural fertilisers and wastewater, has been a key aspect of EU environmental legislation.

In a new study, scientists used several global databases to estimate nutrient input to all river basins that drain into European seas.  To investigate the connection between nutrient input and water quality, the scientists compared the total change in nutrient input from 1990 to 2005 with measurements of nitrate and phosphate from 39 European river outlets.

The results revealed that

  • Nitrate pressure for the EU-15 Member States has fallen by 32% since 1990, thanks mainly to a reduction of 13% in fertiliser use.  Wastewater input has remained fairly stable overall, although differences exist between countries.
  • Phosphate input has also declined, but this is  because over the years it has accumulated in soils meaning that farmers apply less phosphate fertiliser, rather than the result of environmental legislation.

The researchers recommend that the network of European monitoring stations includes a greater number near river outlets as well as within the river basins. This would allow local conditions and the integrated effect on water discharged to the sea to be analysed.