Managing riparian buffer strips to optimise ecosystem services: A review

Riparian buffer strips provide a wide range of ecosystem services in agricultural landscapes with benefits extending beyond those provided by non-riparian field margins. For example, in addition to enhancing the aesthetic value of the landscape and protecting biodiversity, riparian buffer strips also mitigate diffuse pollution and provide inputs to freshwater systems. Their multifunctional nature makes developing management prescriptions complex with the need to identify conflicts, interactions and synergies between the services offered. Here we explore how the placement, physical properties, management and vegetation structure influence the potential of riparian buffer strips to deliver a range of benefits. Under high nutrient loadings, buffer strips can become saturated and act as a source of pollutants, thus limiting their long-term effectiveness. Furthermore, in saturated buffer strips nitrification can increase greenhouse gas emissions. Buffers should not therefore be viewed as an end-of-pipe solution, but within a wider management framework that controls pollutants at the source. Furthermore, biomass removal (e.g. via mowing) can prevent nutrient saturation, increasing the longevity of buffer strips; such operations should, however, be carefully timed to reduce adverse impacts of disturbance on water quality and biodiversity. Wooded buffers can be less effective than grass buffers at intercepting sediments and sediment bound pollutants, but provide many benefits associated with mitigating the impacts of climate change (e.g. carbon capture and moderating aquatic temperatures). This highlights potential trade-offs between climate change and water quality objectives. Zoned buffers that combine strips of riparian woodland and grass, could therefore deliver benefits transcending these policy areas. With such buffers taking large areas of land out of production, they may not be financially sustainable, particularly in intensively managed catchments. In such catchments, to balance food production goals with other ecosystem services, vegetated and/or forested buffer strips, of variable width, should be selected based on objectives at the local or regional scale. Catchment scale initiatives that support a diversity of unbuffered watercourses, vegetated buffers and wooded buffers could help address conflicts between policy areas. Furthermore, with riparian ecosystems being naturally dynamic and diverse, restoring riverbank heterogeneity will also enhance biodiversity. Catchment management plans should take an integrative approach to spatially target the placement of buffer strips to where the greatest benefits can be derived. This review aims to inform environmental managers, regulators and practitioners on how the multifunctionality of riparian zones can be optimised through targeting management actions at the local and catchment scale.