Pollution and nutrient enrichment

Pollution has reduced significantly since the 1980s. Nutrient enrichment from diffuse pollution is still a problem in some areas. Pollution has a major negative impact; it can both reduce and modify biodiversity. This can happen directly - for example through changes to water quality - or indirectly, as pollution influences climate change.

Improvements in water quality

Stricter pollution control legislation and better waste water treatment methods have resulted in marked improvements in water quality (State of Scotland's Environment (2007). Sensitive species like otters and estuarine fish have increased in previously polluted lowland waters, (Scotland's Biodiversity Indicators).

Nutrient enrichment

Nutrient enrichment is a type of diffuse pollution, mainly caused by nitrogen, but also by phosphorous. Nitrogen enrichment has altered nutrient cycling in Scottish habitats, damaging soils and reducing water quality.

The use of nitrogen fertilsers in arable areas peaked during the 1980s but decreased significantly by 2007. In Scotland this problem is compounded by pollution from industries and urban areas deposited by heavy rainfall.  

Signs of nutrient enrichment include replacement of flowering herbs by competitive grasses and growth of algae in freshwaters. These changes are often the tip of the iceberg affecting many other species and reducing biodiversity.

Controlling pollution

The Scottish Environment Protection Agency (SEPA)    is responsible for controlling water and airborne pollution in Scotland. Local authorities are responsible for waste.

The European Union has introduced legislation requiring the achievement of good ecological status for freshwater by 2015 (Water Framework Directive  ) as well as Directives covering bathing waters  and shellfish waters  . In response SEPA is working with partners to address diffuse pollution in priority catchments  across Scotland.