Experimental habitat restoration for conserved species using ecosystem engineers and vegetation management

Abstract

We experimentally address the theoretical potential for managing ecosystem engineer species to support suites of species in degraded habitats. Historically, the ecosystem engineer California ground squirrel Otospermophilus beecheyi supported a grassland food web through widespread burrowing activity. Currently, ground squirrels are not a threatened species, but like many other ecosystem engineers, they exist at densities too low to fulfill their engineering role in many locations. Our objective was to implement short‐term treatments, including squirrel translocation, to re‐establish key ecological processes on protected reserve lands. We manipulated vegetation and squirrels in a replicated, large‐scale field experiment for 2 years, and monitored through a third year. Vegetation mowing and soil decompaction treatments reduced grass density and thatch depth. Squirrel translocation accelerated squirrel settlement and activity in target sites. Of the more than 1000 burrow entrances remaining through the third year, nearly all burrows were concentrated in the plots that received squirrel translocation. We found significant additive effects of squirrel translocation and vegetation management on the spatial footprint of squirrel activity. Noteworthy and persistent engineering effects were achieved through squirrel activity, and both vegetation management and squirrel re‐establishment were needed to stimulate squirrel activity. The overarching goal of this experiment was to provide conservation managers with a cost‐effective tool for restoring degraded habitats to a hybrid ecosystem state with improved suitability for species of conservation concern, in this case, the western burrowing owl Athene cunicularia hypugaea.

A global database and “state of the field” review of research into ecosystem engineering by land animals

“…Ecosystem engineers are anticipated to speed ecological recovery by reinstating ecosystem functions following species declines (Manning, Eldridge, & Jones, ) and by facilitating the re‐establishment of other threatened species (Hayward et al., ). Functional extinctions of engineer species are also an increasing point of concern for conservation and ecosystem restoration (McCullough Hennessy et al., ; Silvey, Hayward, & Gibb, ). Determining appropriate densities of engineer species required for habitat restoration can conflict with population targets for species conservation, as high densities of any species can lead to overexploitation of resources and ecosystem degradation (Verdon, Gibb, & Leonard, ).…”

“…), were only included where outcomes for terrestrial communities were described. Note: ecosystem engineering does not include trophic interactions such as predation and seed dispersal, as these are considered "keystone" rather than "engineering" outcomes (Mills, Soule, & Doak, 1993), although it is possible for species to fulfil roles as both keystone species and as ecosystem engineers. We limited potential sources of bias in our search using multiple search engines and using the same search criteria across all search engines (Haddaway, Woodcock, Macura, & Collins, 2015).…”

Heavy livestock grazing negatively impacts a marsupial ecosystem engineer

“…Digging and burrowing animals not only enhance habitat heterogeneity (Parsons et al ., ), thus creating habitat for other small mammals, reptiles and invertebrates (Davidson, Lightfoot & McIntyre, ; Ewacha et al ., ), but can influence ecosystems through non‐engineering pathways such as predation and competition (Prugh & Brashares, ). Therefore, maintaining or enhancing ecosystem engineer populations may be a cost‐effective tool to lessen the negative impacts of grazing on soil health, restore degraded habitats and assist in the recovery of other species of conservation concern (Eldridge & James, ; Eldridge et al ., ; McCullough Hennessy et al ., ).…”

“…Results are considered significant were the 95% confidence intervals do not cross one. maintaining or enhancing ecosystem engineer populations may be a cost-effective tool to lessen the negative impacts of grazing on soil health, restore degraded habitats and assist in the recovery of other species of conservation concern (Eldridge & James, 2009; Eldridge et al, 2016;McCullough Hennessy et al, 2016).…”

Riverine fen restoration provides secondary habitat for endangered and stenotopic rove beetles (Coleoptera: Staphylinidae)

“…Nevertheless, based on the limited self‐repair capacity of fens and mires and their low resilience, restoration measures may differ substantially in their success (Maltby ; Verberk et al ., ; Beadle et al ., ). In particular, it often remains unclear to what extent assemblages characteristic of fen are able to benefit from restoration measures, except from some knowledge regarding a few target species (Rydin & Jeglum, ; McCullough Hennessy et al ., ; Ter Heerdt et al ., ).…”