Removal pattern mitigates negative, short‐term effects of stepwise Russian olive eradication on breeding birds

Abstract

Invasive species can have disastrous ecological consequences, and management is often required to control these invasions and mitigate the damage. Yet in many systems, biological invaders can serve critical ecological roles, particularly where they have been long‐established or effectively replaced functionally similar native species. In such cases, eradicating invasions can have unintended consequences on other components of the ecosystem, and potential control measures must be viewed within an ecosystem‐wide context to ensure they do not cause more harm than good. On the lower Snake River in eastern Washington, invasive Russian olive (Elaeagnus angustifolia) comprises 90% of the woody riparian vegetation in some areas. In this study, we experimentally removed half of the Russian olive from 0.5‐ha plots using three configuration patterns that varied in the amount of interspersion of remaining vegetation (n = 9 replicates) to evaluate the short‐term impact of a stepwise restoration strategy on breeding bird communities. We monitored plots for 5 yr and found that Russian olive removal on low interspersion treatments negatively affected occupancy rates for 50 of 52 species (96%) and significantly reduced richness by up to 2.41 (95% credible interval [CI] = 0.73, 4.14) species relative to control plots. These effects dampened with increasing interspersion, and occupancy rates of only 41 (79%) species decreased on high interspersion treatments, leading to non‐significant richness reductions of only 0.99 (95% CI = −0.70, 2.75) species. Given the dominance of Russian olive in this region, removing it eliminates critical habitat for birds that require woody structure for nesting and foraging. Thus, we caution managers to consider the potential short‐term negative impacts to the local fauna when planning invasive control efforts. However, we found that several riparian‐dependent species known to breed in the region were noticeably absent from our study plots, and short‐term losses in avian habitat may be tolerable where restoration of native vegetation supports greater diversity in the long term. In such restoration efforts, managers may be able to mitigate the negative effects of invasive shrub control by maintaining high interspersion among unmanipulated vegetation while waiting for native vegetation to re‐establish.

Removing invasive giant reed reshapes desert riparian butterfly and bird communities

“…Given that we sampled only up to 8 years after burns, it is not clear whether burned sites will eventually become more like the unburned floodplain or will instead remain on a distinctive trajectory. Nevertheless, our findings regarding bird community responses are generally in line with those from the Segura River basin (Bruno et al 2019) and broadly support other riparian management projects that found the removal of invasive vegetation subsequently leads to woody species recovery that supports riparian‐affiliated avifauna (Kus 1998, Valente et al 2019, Hall et al 2020).…”

“…Given that we sampled only up to 8 years after burns, it is not clear whether burned sites will eventually become more like the unburned floodplain or will instead remain on a distinctive trajectory. found the removal of invasive vegetation subsequently leads to woody species recovery that supports riparianaffiliated avifauna (Kus 1998, Valente et al 2019, Hall et al 2020.…”

“…Further, we expected butterflies to respond rapidly following burns because early successional herbaceous plants should provide ample resource availability (Fiedler et al 2012, Henderson et al 2018). We also expected that birds would be slower to respond because woody vegetation, an important component of riparian bird habitat, would take at least several years to become established in burned areas (Kus 1998, Golet et al 2008, Valente et al 2019, Hall et al 2020). For our second objective, we modeled associations between habitat characteristics and the abundance of butterfly and bird species that responded to the management efforts.…”

Impacts of invasive species on populations of federally listed species on US Army Corps of Engineers project lands

“…Restoration efforts may focus on smaller areas, where the outcome is a landscape mosaic of restored native patches and nonnative-dominated patches. While the long-term outcome of such an approach is poorly understood, small-patch removal and restoration of native trees in Russian olive-dominated habitats could be a workable option with minimal impacts on the bird community (Valente et al 2019).…”

River channel response to invasive plant treatment across the American Southwest

“…While IRV treatment within river corridors has continued to increase along with overall channel restoration efforts, the post-IRV treatment monitoring has not kept pace (Rubin et al, 2017). Restoration goals and post-eradication of IRV monitoring efforts overwhelmingly focus on vegetation (González et al, 2017a(González et al, , 2017bHarms & Hiebert, 2006) or wildlife (Sogge et al, 2008;Valente et al, 2019) response; however, hydrological and geomorphic processes are key drivers of aquatic habitat and vegetation dynamics in riparian ecosystems (Stromberg et al, 2007). At the Escalante River, Scott et al (2018) found that the shade-tolerant invasive shrub Russian olive grew in native Fremont cottonwood (Populus fremontii) understories, and modified channel morphology by trapping sediment and forming levees.…”