Forestry and Diffuse Pollution


Coire Loch a small woodland lochan in Glen Affric. Our diffuse pollution research area is seeking to understand woodland-water interactions to prevent and reduce water pollution within freshwater catchments; the research helps to improve how we manage our woodlands and maintain the balance required for healthy ecosystems.

Diffuse pollution, pollution without a clear point source, is one of the main reasons for reduced water quality in the UK; it increases the treatment needs of drinking water and affects water ecology, for example fish and the freshwater pearl mussel that require high quality waters for their survival. Pollutants include sediment, soil washed off the land into surface waters, and nutrients such as phosphorous and nitrate arising from fertiliser use. Agriculture is the main source of diffuse pollution but there are also significant contributions from forested and urban environments.

Trees, as buffers, can reduce the amount of pollutants entering watercourses, therefore strategically planting trees and other vegetation along riverbanks (riparian buffers), on hill-slopes and around upland headwaters can help improve water quality. There are also benefits for soil, the foundation of our food supply, because trees help bind the soil, reducing erosion and sediment delivery; moreover, tree roots aid water infiltration into the soil, helping water move downwards rather than overland into streams and rivers, thereby helping to reduce flooding.

Forest operations have the potential to increase diffuse pollution, mainly through increased turbidity and sedimentation due to soil disturbance accompanying cultivation, drainage, road construction and harvesting operations, but also through phosphorous runoff following fertiliser applications. Surface water acidification is another significant water quality issue, particularly in areas with mature conifer forests and sensitive geology.

Research objectives

  • To understand and quantify the positive and negative impacts of forestry on diffuse pollution and the freshwater environment.
  • To test the efficacy and inform future revisions of best practice guidance.

Funders and partners

This research is primarily funded by the Forestry Commission’s Delivering Resilient Forests programme and Forestry Commission Scotland, with considerable support from Forest Enterprise Scotland.

Funders and collaborators/partners include:

  • Scottish Environmental Protection Agency
  • Scottish Water
  • University of Edinburgh
  • University of Glasgow
  • University of Dundee
  • University of Leeds

Forestry Commission policy The protection of the water environment is a key element of sustainable forestry and this research directly supports the Forestry Commission policy of achieving sustainable forest management in the UK.

In addition Country Forestry Strategies (Scotland, England, and Wales) identify the need to protect and enhance water resources. The basis for the water related aims is the EU Water Framework Directive (2000), which establishes the principal framework for protecting and improving the water environment through a requirement to achieve ‘Good Status’, a term that refers both to chemical and ecological quality.

Any other information

The diffuse pollution research is linked to our Woodland for Water and Opportunity Mapping work.


Current work in forest hydrology is focused on evaluating how forestry can help to tackle wider problems of diffuse pollution and flooding although the potential of forestry to degrade water quality is still a significant component of our work.

Research results inform the assessment and development of best management practice as detailed by the Forestry Commission’s Water Guidelines and associated practice guides.


Nadeem Shah