The effect of riparian woodland management on the freshwater environment

Many countries recommend that riparian woodland buffers should be established along watercourses to protect the water environment from forestry or agricultural practices on the adjacent land. The international literature covering the effects of riparian woodland buffers on the freshwater environment was reviewed and published in 2004.

Key points:

  • The main functions of riparian woodland buffers are considered to be sediment removal and erosion control, the protection of water quality, the moderation of shade and water temperature, the maintenance of habitat structural diversity and ecological integrity, and the enhancement of landscape quality.
  • The main factors that influence the protective functions of buffer areas are width of buffer, structure of the vegetation, species choice, and management practice.
    Photo showing riparian woodland used to stablise river banks and retain sediment in run-off from adjacent fields
    Riparian woodland can be particularly effective at stablising river banks and retaining sediment and other pollutants in run-off from adjacent fields
  • There is no definitive width that will protect the water environment from every potential threat. Buffer widths in the range of 5 – 30 m have been found to be at least 50% effective and often > 75% effective at protecting the various stream functions associated with undisturbed forest streams. Internationally, forestry agencies tend to recommend widths between 10 m and 30 m.
  • The optimum vegetation structure is generally an open woodland canopy of mixed species of varied age class, replicating that of native riparian woodland. Around 50% of the stream surface should be open to sunlight with the remainder covered by dappled shade. Light conditions should be adequate to sustain a cover of herbaceous ground flora and marginal vegetation.
  • Native tree species support the greatest diversity and abundance of terrestrial invertebrates and provide a high quality of leaf litter, to the benefit of the aquatic zone. Planting should favour light-foliaged species and generally avoid the use of alder on any large scale within acid sensitive areas and parts at risk from Phytophthora disease.
  • Management of riparian woodland buffers should be based on a consideration of site sensitivity, intrinsic value and potential. It is important to identify which functions of the riparian buffer area are most relevant to a given location and prepare a management plan that is appropriate for the entire forest or water catchment.
  • Some riparian woodland buffers will benefit from active management such as thinning, coppicing or pollarding whilst others will favour minimum intervention. Long term continuity of management is important to ensure that the potential benefits to the aquatic zone are realised.