Providing evidence to improve practice

Individual study:

Published source details

Klimkowska A., Van Diggelen R., Bakker J.P. & Grootjans A.P. (2007) A review of the success of commonly used wet meadow restoration methods (rewetting, topsoil removal, and diaspore addition) in Western Europe. Biological Conservation, 140, 318-328

Background

In Western Europe large areas of fenland habitats have been drained and converted to farmland. In attempts to restore fen and wet fen meadows, techniques such as rewetting, topsoil removal, propagule (e.g. seed, rhizomes etc.) introduction are often used. In this study, an assessment of the effectiveness of commonly used meadow restoration methods was undertaken.

Action

Wet meadows restoration data were obtained through professional networks and experts. Peer-reviewed, published sources and records of conservation projects performed in Western Europe were compiled for analyses, which focussed on measuring:

i) the degree of resemblance in plant species composition of restored meadow communities to local reference vegetation types;

ii) the degree of change in plant richness compared to the initial community composition;

iii) the relative effect of the main restoration techniques (rewetting, topsoil removal, propagule introduction) on overall restoration success.

The change in 'saturation index' was used to evaluate the degree of success; this index reflects the completeness of restored communities in comparison to target communities.

Consequences

Data from 36 sites were collected, the majority in The Netherlands. The assessment revealed that wet meadow restoration attempts have had limited success in most cases, with an average increase in species richness below 10% of the target community. Restoration success was partly determined by the starting situation; the more species-rich at the start, the higher the saturation index after restoration, however, there was a corresponding smaller increase in the number of target species due to restoration.

A combination of top soil removal (removal deeper than 20 cm resulted in a higher saturation index than removal of a shallow layer) and propagule introduction, and a combination of all three techniques, appeared most effective (an increase in the saturation index of up to 16%). Rewetting alone appeared an ineffective restoration method.