Does rewilding improve ecosystem resilience?: a soundscape perspective

Understanding why some ecosystems appear more resilient to perturbation than others is
of fundamental importance if we wish to avoid biodiversity collapse and maintain a
habitable planet.
There is a rapidly growing shift towards low intensity, large scale, semi-passive
restoration approaches, such as rewilding, that seek to restore ecological processes
rather than deliver pre-defined structure-based outcomes. Within the overall context of
rewilding harnessing the restorative power of beavers through their habitat engineering
activities is becoming increasingly commonplace in Britain, with most English counties
now having enclosed beaver projects either planned or in operation, a situation
unimaginable a decade ago. In Scotland Eurasian beavers have occurred again in the
wild for about 20 years with their population now approaching 2000 animals and with
plans to translocate them more widely. The ecological benefits that stem from dam
building and the other engineering activities of beavers are, in some senses, well
established, with a catalogue of studies demonstrating increases in birds, plants,
amphibians, invertebrates and bats [1]. These complement the ability of beaver ponds to
intercept pollutants and improve downstream water quality, attenuate flow peaks and
mitigate the disturbance effects of drought and wildfires [2]. However, the picture is
incomplete since many indicator biological taxa are studied in isolation while the benefits
of beavers most likely do not accrue evenly and are sensitive to the surrounding
landscape matrix. The degree of subsidy from aquatic to terrestrial systems and how this
varies in relation to beaver activity, also remains poorly understood, despite its potential
importance to higher trophic levels when other resources are depleted [3]. Finally,
although beaver ponds seem to provide a stabilising influence in the face of extreme
events, it is unknown whether there is an accompanying ecological benefit in terms of
enhanced resilience of populations, communities or ecosystem functions. The solution to
some of these questions has remained elusive in part because traditional monitoring
approaches are invasive and costly and therefore cannot be deployed at the spatial and
temporal frequency that is desirable.