Using ecosystem engineers as tools in habitat restoration and rewilding: beaver and wetlands

Alan Law; Martin J Gaywood; Kevin C Jones; Paul Ramsay; Nigel J Willby

doi:10.1016/j.scitotenv.2017.06.173

Using ecosystem engineers as tools in habitat restoration and rewilding: beaver and wetlands

Sci Total Environ. 2017 Dec 15:605-606:1021-1030. doi: 10.1016/j.scitotenv.2017.06.173. Epub 2017 Jul 12.

Authors

Alan Law¹, Martin J Gaywood², Kevin C Jones³, Paul Ramsay⁴, Nigel J Willby⁵

Affiliations

¹ Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling FK9 4LA, Scotland, UK. Electronic address: alan.law1@stir.ac.uk.
² Scottish Natural Heritage, Great Glen House, Inverness IV3 9NW, Scotland, UK. Electronic address: martin.gaywood@snh.gov.uk.
³ Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling FK9 4LA, Scotland, UK. Electronic address: k.c.jones@stir.ac.uk.
⁴ Bamff Estate, Alyth PH11 8LF, Scotland, UK. Electronic address: paulramsay@bamff.co.uk.
⁵ Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling FK9 4LA, Scotland, UK. Electronic address: n.j.willby@stir.ac.uk.

PMID: 28693107
DOI: 10.1016/j.scitotenv.2017.06.173

Abstract

Potential for habitat restoration is increasingly used as an argument for reintroducing ecosystem engineers. Beaver have well known effects on hydromorphology through dam construction, but their scope to restore wetland biodiversity in areas degraded by agriculture is largely inferred. Our study presents the first formal monitoring of a planned beaver-assisted restoration, focussing on changes in vegetation over 12years within an agriculturally-degraded fen following beaver release, based on repeated sampling of fixed plots. Effects are compared to ungrazed exclosures which allowed the wider influence of waterlogging to be separated from disturbance through tree felling and herbivory. After 12years of beaver presence mean plant species richness had increased on average by 46% per plot, whilst the cumulative number of species recorded increased on average by 148%. Heterogeneity, measured by dissimilarity of plot composition, increased on average by 71%. Plants associated with high moisture and light conditions increased significantly in coverage, whereas species indicative of high nitrogen decreased. Areas exposed to both grazing and waterlogging generally showed the most pronounced change in composition, with effects of grazing seemingly additive, but secondary, to those of waterlogging. Our study illustrates that a well-known ecosystem engineer, the beaver, can with time transform agricultural land into a comparatively species-rich and heterogeneous wetland environment, thus meeting common restoration objectives. This offers a passive but innovative solution to the problems of wetland habitat loss that complements the value of beavers for water or sediment storage and flow attenuation. The role of larger herbivores has been significantly overlooked in our understanding of freshwater ecosystem function; the use of such species may yet emerge as the missing ingredient in successful restoration.

Keywords: Agriculture; Castor fiber; Diversity; Exclosure; Grazing; Species richness.