Global environmental changes more frequently offset than intensify detrimental effects of biological invasions

Authors: LOPEZ, BIANCA - University Of Massachusetts; ALLEN, JENICA - Mount Holyoke College; DUKES, JEFFREY - Purdue University; LENIOR, JONATHAN - University Of Picardie Jules Verne; VILA, MONTSERRAT - Doñana Biological Station; Blumenthal, Dana; BEAURY, EVELYN - University Of Massachusetts; FUSCO, EMILY - University Of Massachusetts; LAGINHAS, BRITTANY - University Of Massachusetts; MORELLI, TONI - Amherst College

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2022
Publication Date: 7/27/2022
Citation: Lopez, B.E., Allen, J.M., Dukes, J.S., Lenior, J., Vila, M., Blumenthal, D.M., Beaury, E.M., Fusco, E.L., Laginhas, B., Morelli, T.L. 2022. Global environmental changes more frequently offset than intensify detrimental effects of biological invasions. Proceedings of the National Academy of Sciences(PNAS). 119(22). Article e32117389119. https://doi.org/10.1073/pnas.2117389119.
DOI: https://doi.org/10.1073/pnas.2117389119

Interpretive Summary: Invasive species impacts are likely to depend on other global changes, but the nature of those impacts remain poorly understood. We conducted a global meta-analysis, including 467 cases from 95 published studies, to investigate the combined effects of invasive species and other global changes on species, communities, and ecosystems. Invasion and global change interactions were mostly antagonistic, lessening overall impacts, but synergistic interactions occurred in >25% of cases and mostly led to more detrimental outcomes for ecosystems. These results will help scientists and land managers predict invasive impacts with continued climate and atmospheric changes.

Technical Abstract: Human-induced global environmental changes, including the spread of non-native invasive species, are rapidly altering ecosystems. Understanding how ecosystems respond to simultaneous effects of invasion and other global environmental changes (GECs) is critical for informing ecosystem adaptation and management. However, the magnitude and direction of invasion and abiotic GEC interactions and the frequency of unexpected interactions (ecological surprises) are unknown. We conducted a global meta-analysis to investigate invasions, GECs, and their combined effects on native species, communities, and ecosystems. We found 467 cases from 95 published studies that reported individual and combined effects of invasions and a GEC stressor, most commonly warming, drought, or nitrogen deposition. We calculated standardized effect sizes (Hedges’ d) for individual and combined treatments and classified interactions as additive (sum of individual treatment effects), antagonistic (smaller than expected), or synergistic (outside the expected range). The ecological effects of invasions were more detrimental than GECs on average. However, GEC effects varied, with negative effects more likely with drought. Invasion and GEC interactions were mostly antagonistic, but ecological surprises (synergistic interactions) occurred in >25% of cases and mostly led to more detrimental outcomes for ecosystems. While interactive effects are most often smaller than the sum of individual invasion and GEC effects, ecological surprises are not rare and occur across ecological responses from the individual to the ecosystem scale. Furthermore, the consistently detrimental effects of invasion suggest that managing invasions is often the most important step towards reducing harm from invasion and GEC interactions.