Woods can be important in managing water quality and water quantity issues, such as diffusing pollution and flooding. These benefits can help provide clean and attractive waters for wildlife and recreation while also helping the UK to meet its commitments to the EU under the Water Framework Directive, Flooding Directive and Nitrates Directive
However there are many misconceptions about how trees and woods interact with the water environment. This is why we undertook some research into the impacts of woods on water.
Read our 'Water Report' on the right hand side.
How woods reduce water pollution
Woods reduce the amount of pollution reaching rivers and other waterbodies as trees take up nutrients and pollutants as they grow. This means all existing woods are helping to maintain water quality and planting new woods could improve water quality.
This effect varies between types of woods and how they are managed. Coniferous plantations can contribute to acidification of waters as their needles catch pollutants in the air which are later washed off into rivers when it rains. This means that the restoration of planted ancient woodland sites to broadleaf woodland, not only helps wildlife but could also improve water quality.
Woods that are managed for timber are often treated with fertilisers and pesticides when the trees are getting established. This can also contribute to pollution as the nutrients and pollutants taken up the trees as they grow are offset by those applied to the land.
How woods can reduce flooding
Woods could help reduce flooding in a different way. Because the trees and shrubs in a woodland are tall and dense in structure, they can form a partial barrier to the movement of flood water, more than grassland or bare fields, they can delay water which reduces the flood peak.
This means that existing woodland in the floodplain or in upland headwaters may already be contributing to the reduction of flooding and that targeted woodland creation could help in other areas. Because the effect of the woods is more to do with their structure short rotation coppice or short rotation forestry for biomass production could also help. However we would prefer to see native woodland created wherever possible.
Woods and water policy
The benefits that woods can provide to the water environment should be better recognised in policy and legislation. Woods are one tool to help improve water quality, contributing to the Water Framework Directive and Nitrates Directive; while also reducing flood risk and contributing to achieving the Floods Directive. The same woods will also be contributing to biodiversity, landscape, amenity and quality of life.
For more information try reading our position statements for more detail our water research.