What is the “real” impact of invasive plant species?

Abstract

Invasive plant species should be evaluated and prioritized for management according to their impacts, which include reduction in native diversity, changes to nutrient pools, and alteration of fire regimes. However, the impacts of most invasive species have not been quantified and, when measured, those impacts are based on a limited number of response metrics. As a result, invasion ecology has been overwhelmed by speculation and bias regarding the ecological consequences of invasive plants. We propose a quantitative mathematical framework that integrates any number of impact metrics as a function of groundcover and geographic extent. By making relative comparisons between invaded and uninvaded landscapes at the population scale, which results in a percent change for each metric, we overcome previous limitations that confounded the integration of metrics based on different units. Our model offers a quantitative approach to ecological impact that may allow identification of the transition from benign introduction to impactful invader, while also allowing empirical comparisons at the species and population levels that will be useful for management prioritization.

Management of invasive Phragmites australis in the Adirondacks: a cautionary tale about prospects of eradication

“…However, deciding which plant species to target for control is difficult, especially when multiple species co-occur and each is associated with or facilitated by other biotic or abiotic stressors (Simberloff and Von Holle 1999;Bertness et al 2002;Minchinton and Bertness 2003;Nuzzo et al 2009;Fisichelli et al 2013;Kuebbing et al 2013;Dávalos et al 2014Dávalos et al , 2015Craven et al 2016). An abundance of prioritization schemes exist, largely developed by scientists, to help land managers make better informed decisions that focus control efforts (Robertson et al 2003;Fox and Gordon 2009;Downey et al 2010;Esler et al 2010b;Darin et al 2011;Barney et al 2013;Abella et al 2015;Adams and Setterfield 2015;Lindenmayer et al 2015). Depending on a particular scheme's focus, species, habitats, ecosystem services, control strategies, probability of achieving success, expected impacts, and costs may be evaluated.…”

“…Depending on a particular scheme's focus, species, habitats, ecosystem services, control strategies, probability of achieving success, expected impacts, and costs may be evaluated. The majority assume that evidence of non-indigenous plant impacts is available and control feasible, yet despite repeated and persistent calls for detailed assessment of impacts (Blossey 1999;Downey 2011Downey , 2014 we lack such information except for a few well-studied systems (Peh 2010;Barney et al 2013). Furthermore, many management interventions remain un/under evaluated, or results are not readily accessible and managers continue to rely on experience-based learning (Pullin et al 2004;Foxcroft et al 2014, and references therein).…”

Interactions between seedlings of the invasive treeAilanthus altissimaand the native treeRobinia pseudoacaciaunder low nutrient conditions

“…Early-successional, native species may compete with the invader for the same available resources, facilitate the invader by creating a favorable environment, both compete and facilitate an invader under different environmental conditions, or neither compete with or facilitate an invader. Invasive species are a focus of research because they may have negative impacts on ecosystem processes compared with native species (Barney et al 2013). The interaction between exotic invasive species and early succession fast-growing native species may regulate the success of the invader and such interactions first occur at the seedling level.…”

Invasion Shadows: The Accumulation and Loss of Ecological Impacts from an Invasive Plant

“…Over time, nascent invasions will increase in size and density, two factors that we know influence the magnitude of ecological impacts in some circumstances (Barney et al 2013). However, invasive plant impacts have been studied almost exclusively using established populations, usually of unknown age, precluding identification of how impacts change with time (Kumschick et al 2015).…”