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

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.

Beaver‐created successional gradients increase β‐diversity of invertebrates by turnover in stream‐wetland complexes

“…Recently, it has been suggested that using ecosystem engineers, such as beaver, to restore ecosystems may lessen the need for direct human intervention (Byers et al., ; Law et al., ; Van Klink & Wallisdevries, ). Our results strengthen the idea that beaver activity can be an important conservation tool by contributing to diversity in areas where they are present.…”

Sediment and nutrient storage in a beaver engineered wetland

“…These results support the existing body of research showing that wetlands, in the broad sense, act as valuable sediment and nutrient stores (Johnston, 1991), particularly in contrast to anthropogenic degraded landscapes (Nahlik and Fennessy, 2016). Furthermore, results indicate that beaver engineered wetlands are exemplars of such valuable wetlands and can successfully exist or be created within intensively managed European agricultural landscapes (Law et al ., 2017; Puttock et al ., 2017). …”

“…Dam and pond features can alter hydrological regimes, both locally and downstream (Polvi and Wohl, 2012; Burchsted and Daniels, 2014). The resulting increased structural heterogeneity of the environment (Rolauffs et al ., 2001) also creates a diverse range of habitats (Rosell et al ., 2005) with an increasingly recognised potential as a habitat restoration tool (Law et al ., 2017). In addition to increasing biodiversity (Law et al ., 2017), it has been suggested that, due to their engineering activity, beavers could play a role in the management of river catchments (Puttock et al ., 2017).…”

An Australian perspective on rewilding

“…; Stringer & Gaywood ; Law et al. ). The restoration of pre‐European landscapes and species assemblages in Australia is in most cases unachievable due to extinctions and the difficulties of removing invasive species.…”