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The effect of small stream restoration on terrestrial biota

The restoration of rivers and streams generally aims to improve water retention in the landscape and increase the ecological value of the watercourse. Many renaturation projects take place on small streams with a maximum width of 1.5 m that have been straightened or even canalized and affect several hundred meters of the course of the stream. The technical realization includes the renewal of meanders, the planting of woody plants on the banks of the stream or the simple abandonment of maintenance measures in order to allow natural succession in the immediate vicinity of the stream. The ecological value of restoration measures on short stretches of smaller streams is poorly documented, as most research studies to date have focused on larger streams and rivers (e.g. ref, ref). It is unlikely that their benefit is in improving aquatic biota, as unrestored sections of small streams are a barrier to colonization of restored areas. Furthermore, it is unlikely that the restoration of several hundred meters of stream will improve water quality. The ecological benefits of small stream restoration are therefore likely to be the positive effects on terrestrial biota. 

In this project, we investigate the effects of small stream restoration on terrestrial biota, in particular plants, insects and birds. We are focusing on these three taxonomic groups because they provide important ecosystem services and have a high conservation value. A dramatic decline in insects has been observed over the last decade, so the positive effects of restoration on this group would be particularly important. We compare 55 restored sections of watercourses in Hesse with non-restored sections of the same watercourses. We use classical methods (vegetation surveys, observations) to record plants and birds. We catch insects with Malaise traps and identify them using DNA metabarcoding.

The main aim of the project is to assess the benefits of restoration and to determine which measures help certain taxa. This will in turn help to improve the ecological value of future restoration projects.

Funded by Lore Steubing Institut

Involved: Lena Lerbs, Sascha Liepelt, Stefan Pinkert, Nina Farwig, Anna Bucharova