Whole‐community facilitation by beaver: ecosystem engineer increases waterbird diversity

Abstract

Wetlands are rich in biodiversity, but globally threatened. After a long period of regional extirpation, beavers have recently returned to many European areas and are now restoring wetlands. The beaver is remarkable regarding the large impacts it has not only on individual species but on entire communities and ecosystems. In fact, beavers are referred to as ‘ecosystem engineers’.The facilitative effect of the beaver Castor canadensis on a waterbird community of seven species of waders and ducks in boreal ponds was studied by using the before–after control–impact method (BACI) and analysing the effect of the duration of flooding. The before–after setting could be used since beavers had caused disturbance by flooding several forest ponds during the course of this long‐term study (1988–2009). The study took place in southern Finland, where waterbirds were surveyed four times during the breeding season.The number of waterbird species per pond per year was significantly higher during beaver inundation than before beaver activity, as was the waterbird abundance per survey. Changes were negligible in the controls. The numbers of all seven species increased during flooding, although the increase was significant in only three species. Common teal Anas crecca and green sandpiper Tringa ochropus showed the most positive numerical response to flooding. Mallard Anas platyrhynchos and wigeon Anas penelope were new species entering the duck guild in the flooded wetlands. The beneficial effect of the flood lasted the whole period of inundation, although the most substantial increase in species number appeared during the first two years of flooding.The beaver acted as a whole‐community facilitator for waterbirds. It was inferred from previous studies that this was done by modifying the habitat to make it more productive and structurally favourable. It is concluded that favouring beavers is a worthwhile tool in restoring wetlands to promote waterbird communities. Copyright © 2014 John Wiley & Sons, Ltd.

The impacts of invasive ecosystem engineers in freshwaters: A review

“…Beaver dams change flow regimes from lotic to lentic, causing profound changes to community composition and ecosystem function (e.g. Nummi & Holopainen, ). These changes include the provision of increased habitat for herbaceous plant species but the exclusion of native tree species such as Nothofagus in regions where beavers are invasive (Anderson et al, ).…”

“…Ecosystem engineers may, through creating new structures, mitigate environmental conditions that would otherwise be unsuitable for many other species (Crain & Bertness, , Table ). For example, the beaver increases habitat suitability for waterbirds through the creation of wetlands (Nummi & Holopainen, ). The effects of ecosystem engineering on community structure may be most influential and positive where there are multiple stressors (Crain & Bertness, ).…”

Herbivory on freshwater and marine macrophytes: A review and perspective

“…Species of aquatic herbivore which can act as ecosystem engineers, such as the beaver, are typically prime candidates for rewilding projects due to the wider ecosystem benefits that result from such engineering (Collen and Gibson, 2001). The recent finding that beaver's creation of ponds increased the diversity of herbivorous waterfowl within the landscape indicates that natural recolonization and rewilding may result in wider changes to herbivore assemblages than the target species alone, through the facilitation of different herbivore taxa (Nummi and Holopainen, 2014).…”

Ecological engineering and aquatic connectivity: a new perspective from beaver‐modified wetlands

“…Complex configuration of these perimeters (Fig. ) also increases within‐pond habitat heterogeneity by increasing shoreline complexity, cover for waterfowl (Nummi & Holopainen, ) and potential dispersal corridors for other species to upland and adjacent aquatic habitats (Anderson, ).…”