Does rewilding improve ecosystem resilience?: a soundscape perspective

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