Forests and farming – working together to protect water quality

Trees and forests offer an array of positive environmental functions. Protecting water quality is one of the most important and one that can hugely benefit farming. Noel Kennedy, Forestry Development Officer discusses how farming and forestry can benefit and improve water quality.

Image above: Pollution Impact Potential Map with areas for planting identified (Source EPA)

One of our key environmental challenges is to protect and improve water quality. While some rivers showed signs of biological improvement, a total of 47% of our rivers were classed as in unsatisfactory condition according to the Environmental Protection Agency publication (EPA) Water Quality in 2020 – An Indicators Report.

So how can planting trees help?

Interception of nutrient runoff

One of the main challenges to protecting water quality is limiting nutrients (e.g. phosphorus on poorly draining soils) and fine sediment to reach our watercourses. Strategic planting of appropriate trees and forests in the right locations can play a significant role in intercepting this overland flow and “breaking the pathway” from the source to the receiving waters. Grant support for tree planting including native woodland is available to eligible applicants through the DAFM Afforestation Grant and Premium scheme.

When fenced off, a strong vegetation layer can quickly develop between newly planted trees and the adjoining waterbody, acting to slow and effectively filter potential nutrient and sediment runoff. As the trees grow, their developing root systems improve local soil drainage to further intercept and mitigate runoff particularly following heavy rainfall.

Updated Pollution Impact Potential (PIP) maps, identifying critical source areas for these nutrients, are now available from the EPA. PIP maps can be one of a suite of valuable resources to help guide the planning, strategic location and scale of suitable woodland planting. This can help optimise the interception and help minimise potential impacts.

Shading and cooling of watercourses

As the trees grow along watercourses and the riparian woodland develops, they provide shade with a cooling effect on water temperatures. This is very important to support healthy aquatic life and healthy water. How close the trees are planted to the watercourse is important.

The DAFM Woodlands for Water measure combines an undisturbed setback (where natural vegetation is allowed to develop) along with the creation of adjoining native woodland in appropriate locations to protect and enhance water quality. Carefully located groups of native trees can be planted within the setback area to introduce a shading and dappling effect. This will have a positive impact on biodiversity while creating a more natural looking, uneven woodland edge.

Bank stabilisation

Soil erosion and bank collapse can damage aquatic life and also risk drinking water sources.

The rapid growth of grassy vegetation root systems and the establishment of strong tree rooting systems in the undisturbed riparian setback areas provides increased bank stability and reduces the risk of erosion. 

Regulation of floodwater

Forests have a significant part to play in the regulation of the hydrological cycle. They are an important tool in catchment management. Forests are able to reduce flood flows compared with other land use. For instance, forests will reduce the volume of flood water at source, while the higher infiltration rates of soils under trees reduces rapid surface runoff and flood generation. Studies have found infiltration rates to be up to 60 times higher within forest shelterbelts compared with grazed pasture.

Trees, which have tall and well-ventilated canopies, can significantly reduce the volume of flood water by evaporating more rainfall than most types of vegetation. This in turn reduces the amount of storm rainfall reaching the forest floor resulting in drier soils that can store more of this water below ground.

Well-structured forest soils result in less soil erosion and sediment washing into local watercourses compared to other land uses. This reduces siltation and the need for dredging downstream to maintain open channels to safely convey flood flows.

(Photo 1 – Riparian forests protect water quality in many ways - intercepting nutrient runoff, shielding against pesticide drift, regulating flooding while providing biodiversity, supplying food and stabilising riverbanks.)

Food input into aquatic systems

Small groups of trees and larger areas of native woodland planted along waterways create an abundant supply of food. New habitats provided by the trees and also in the undisturbed setback areas become homes for a wide range of insect species which in turn can become an additional food source for fish and other aquatic organisms. This contributes to healthy watercourses and wider catchments.

A mixture of native trees such as Oak, Birch, Cherry, Alder, Hazel and Rowan enhances local biodiversity. Such a mixture in combination with diverse vegetation provide a rich habitat and food source for pollinators and other animals.

Afforestation grant and premium scheme

If you are considering planting trees to protect water quality, you may also be eligible for grant support!

Support is available to plant a wide range of forest types including native woodlands, commercial conifers and agroforestry. DAFM’s Afforestation Grant and Premium scheme supports planting through afforestation grants and annual premium support. Annual premiums are paid for 15 years and typically range from €510 to €680 per hectare. New forests may also be eligible for Basic Payment.

You can choose to plant a single type of forest, for example to protect watercourses but you can also combine different forest types to achieve multiple and complementary objectives.

For more information on planting trees and how it can benefit you on the farm talk to your local Teagasc forestry advisor or see Forestry Establishment grants 

Your local forestry advisor will be able to provide you with free, independent and objective advice on any technical or financial aspect you may have regarding forestry.  Find out more from the Teagasc Forestry team here