Forest & Water Group (FWG)

Irish Forests and Water Quality -
Forests, Woodland and Trees for Improved Water Quality

In most European countries and indeed worldwide, the focus is on Forests is in relation to the beneficial effects of water quality. Trees and forests play an important role in reducing storm water in several ways and removing or filtering pollutants that would otherwise end up in our rivers and streams. It is widely recognised that sustainably managed forests play an important role in maintaining water quality.

It is widely recognised that sustainably managed forests play an important role in maintaining water quality. Through stabilisation of soil, forests minimise erosion and hence reduce the impairment of water quality due to sedimentation. Forests and Woodlands protect water bodies and watercourses by trapping sediments and pollutants from other up-slope land use and activities.

Riparian Woodland

Well-sited and well-managed floodplain and riparian woodland can contribute to the delivery of a host of outcomes.

Reduced flooding

Forests and Woodlands filter and regulate the flow of water, in large part to their foliage which absorbs precipitation before gradually releasing it to natural channels. Trees can reduce water yield by improving the infiltration rates of woodland soils and by ‘sponging up’ water through the process of evapotranspiration. Average interception of rainfall by a forest canopy ranges from 10-40% depending on species, time of year and precipitation rates per storm event.

Water Quality

In Europe, 96.3 million hectares of forests are designated for the protection of soil and water. This corresponds to 10 percent of the total forest area. By naturally filtering water, forests can reduce drinking water treatment costs. By filtering water through its porous soils, a forest can minimize wastewater treatment costs.

A forest or forested wetland can filter water at approximately one-seventh of the cost than can conventional wastewater treatment systems. For example, New York City famously saved billions of dollars in water filtration costs by conserving the forests and natural landscapes of the Catskills instead of paying for a new water filtration system.

Reducing diffuse pollution

Nutrient losses from agriculture and domestic wastewater discharges are the primary reasons why the water quality objectives of the WFD will not be met (EPA - Water Quality in Ireland 2010 – 2015). In relation to agriculture, the pressures relate to diffuse nutrient run-off (phosphorus and nitrogen) and sediment from land, and point source pollution associated with farmyards. Elevated nutrient concentrations (phosphorus and nitrogen) continue to be the most widespread water quality problem in Ireland.

Productive forests are very good at removing nutrients (nitrates and phosphates) and contaminates (such as metals, pesticides, solvents, oils and hydrocarbons) from soil and water. These pollutants are either used for growth (nutrients) or are stored in wood.

Forest buffers near streams can prevent nitrogen from entering waterways at approximately one-third of the cost relative to wastewater treatment plant upgrades. Studies in the USA have shown reductions of up to 88% of nitrate and 76% of phosphorus after agricultural runoff passed through a forest buffer.

Farm Forests and Woodland can provide Environmental Services in relation to water quality.

The environmental benefits of both new and existing farm forest and woodland can be enhanced using additional measures making them to be of even greater value environmentally. Forest and Woodland areas must be seen as part of the farm and included as part of an overall farm environmental scheme. There are a number of Measures which could be included in CAP 2020 and are compatible with the objectives and rules of Article 28. To make this work there must be “payment for environmental services”.

Farm forests and woodlands providing environmental services in relation to water quality