A global assessment of invasive plant impacts on resident species, communities and ecosystems: the interaction of impact measures, invading species' traits and environment

TLDR

Invasive alien plants threaten resident species and ecosystems, yet a comprehensive assessment linking plant traits and invasion environments to impact characteristics is lacking. We compiled 287 studies covering 167 invasive plant species to provide the first global overview of the frequency, direction, and significance of ecological impacts across 15 resident population, species, community, and ecosystem outcomes. Invasive plants typically lower resident plant and animal richness—especially on islands—while often boosting soil biota abundance and nutrient levels; significant impacts were consistently observed on survival, activity, productivity, mineral content, and fire regimes, whereas community‑level effects such as species richness and diversity depend on plant traits and biome, with annual grasses and wind‑pollinated trees in Mediterranean or tropical regions being especially impactful.

Abstract

Abstract With the growing body of literature assessing the impact of invasive alien plants on resident species and ecosystems, a comprehensive assessment of the relationship between invasive species traits and environmental settings of invasion on the characteristics of impacts is needed. Based on 287 publications with 1551 individual cases that addressed the impact of 167 invasive plant species belonging to 49 families, we present the first global overview of frequencies of significant and non‐significant ecological impacts and their directions on 15 outcomes related to the responses of resident populations, species, communities and ecosystems. Species and community outcomes tend to decline following invasions, especially those for plants, but the abundance and richness of the soil biota, as well as concentrations of soil nutrients and water, more often increase than decrease following invasion. Data mining tools revealed that invasive plants exert consistent significant impacts on some outcomes (survival of resident biota, activity of resident animals, resident community productivity, mineral and nutrient content in plant tissues, and fire frequency and intensity), whereas for outcomes at the community level, such as species richness, diversity and soil resources, the significance of impacts is determined by interactions between species traits and the biome invaded. The latter outcomes are most likely to be impacted by annual grasses, and by wind pollinated trees invading mediterranean or tropical biomes. One of the clearest signals in this analysis is that invasive plants are far more likely to cause significant impacts on resident plant and animal richness on islands rather than mainland. This study shows that there is no universal measure of impact and the pattern observed depends on the ecological measure examined. Although impact is strongly context dependent, some species traits, especially life form, stature and pollination syndrome, may provide a means to predict impact, regardless of the particular habitat and geographical region invaded.