OSCAR: the ecological benefits of woody riparian buffers

A riparian woodland strip along a Swedish stream. Image: Mikko Muinonen | Flickr Creative Commons

Strips of vegetation and trees growing alongside rivers can have significant ecological benefits for the health and status of a river ecosystems. So-called ‘riparian buffers’ can reduce the inputs of nutrients and sediment into a river from the surrounding landscape, particularly in areas of intensive agriculture. However, whilst such ‘woody’ riparian zones are a natural feature of many river catchments, many have been cleared across Europe, often for agriculture, flood defences and urban expansions.

A major new European project has recently been established to synthesise both existing and emerging knowledge on woody riparian buffer strips. Co-ordinated by Prof. Daniel Hering and Dr. Jochem Kail from the University of Duisburg-Essen in Germany, the Oscar project will investigate both the aquatic biodiversity benefits of woody buffer strips, and the ecosystem services they can provide.

In recent years, the ecosystem service framework has helped scientists identify the many benefits generated by woody buffer strips, to humans and non-humans alike. These include biodiversity habitat, stream shading and temperature regulation which may help mitigate the impacts of rising air temperatures, inputs of leaves and wood to river bed habitats, and reduced bank erosion and flood protection. However, a comprehensive survey of the ecosystem health and services benefits of woody buffer strips is still missing – a gap in scientific and management knowledge which the Oscar project aims to address.

Woody buffer strips are often cited as an effective and cost-effective option for river restoration schemes seeking to reach ambitious environmental quality standards such as those set by the EU Water Framework Directive. However, riparian zones are often highly contested spaces, providing fertile and flat areas for agriculture and urban growth. As a result, the restoration of woody buffer zones can often be fragmented and small-scale in extent.

There is increasing awareness amongst aquatic scientists that the beneficial effects of woody buffer strips depend heavily on their spatial arrangement. In order to gain maximum benefits, woody buffer strips should be highly connected, not only along river channels, but also out into the wider landscape.

Woodland strips along rivers can act as migration corridors and refuges for a range of mammals, birds and insects, and provide habitat conditions for plant species. A central underpinning of the Oscar project is that woody buffer strips can form important links in landscape-scale ‘green-blue’ infrastructures, which connect aquatic and terrestrial habitats. Connectivity is a key aspect of contemporary conservation practice, and the Oscar project has the potential to significantly contribute to current debates.

In the Oscar project, an integrated assessment of effects of woody riparian buffers on ecosystem function and service provision will provide the basis for environmental policy and management recommendations. In particular, the effectiveness of different spatial configurations of woody buffer strips will be assessed under different management and climate change scenarios. Oscar will produce a GIS-based multi-criteria decision analysis tool which will help guide management and policy decision-making.

The aim of the Oscar project is to provide water managers and policy makers with recommendations about how woody buffer strip conservation and restoration might be optimised. Communication of project findings will take place through local stakeholder engagement in the case-study catchments, and with working groups at the national (e.g. German LAWA, French ONEMA) and EU level (e.g. ECOSTAT). At the European scale, the project will highlight the relevance of woody buffer strips to the European Biodiversity Strategy, the implementation of the Water Framework Directive, and the ongoing ‘greening’ of the Common Agricultural Policy.

The project is funded by Biodiversa and will run until 2019. We will keep you updated on project progress and outputs.