Global study reveals tempo of invasive species‘ impacts

(Press-News.org) Biological invasions occur when non-native or exotic species colonize new geographic regions, often to the detriment of local plants and animals. Today, human action contributes significantly to invasion processes, allowing species to bridge vast distances and enter new habitats at a highly accelerated rate. This makes it increasingly important to better understand the impact of invasions on ecosystems.

Researchers from the University of Bern, the University of Konstanz (Germany) and the Northeast Forestry University (China), have now shown how the impacts of different kinds of invasions may vary over time. “Invasion impacts aren’t ecological noise, they have a temporal fingerprint,” says Prof. Madhav P. Thakur from the Institute of Ecology and Evolution at the University of Bern, who led the study, recently published in Science. “Our analysis reveals which effects persist, which attenuate, and how time since introduction should guide management priorities.”

A global synthesis across biodiversity and ecosystems

To move beyond simple case studies, the team conducted a first-of-its-kind global meta-analysis spanning plants, animals, microbes, and 15 ecosystem properties. The analysis synthesizes 2’223 results from 775 studies, including terrestrial ecosystems worldwide. It highlights how ecological contexts – invader residence time, native and non-native diversity, latitude, and species traits – shape impacts on both biodiversity and key ecosystem processes, including greenhouse-gas emissions.

The clearest pattern the researchers found: invasive plants reduce native plant diversity, and this loss grows with residence time. In contrast, several abiotic effects – such as changes in soil organic carbon and total nitrogen – often weaken after roughly 6–10 years. The synthesis also suggests that invasive plants and animals are often linked to higher soil emissions of greenhouse gases (CO₂, N₂O, and for plants, CH₄), but the finding remains preliminary. The researchers thus call for more long-term investigations into how biological invasions alter emissions. “If future studies confirm that biological invasions are linked with increased greenhouse gas production, combating invasive species could aid us in the fight against climate change”, Prof. Mark van Kleunen of the University of Konstanz explains.

Findings that challenge assumptions

Several  findings from this meta-analysis also overturn conventional wisdom. For example, the widely taught idea that high native plant or animal richness provides broad ‘biotic resistance’ to biological invasions did not consistently limit ecosystem-level impacts of invasive plants or animals. Likewise, traits commonly associated with invasive plants (e.g., leaf thickness) failed to predict the magnitude or direction of ecosystem change in reaction to an invasion. Latitude, too, showed little consistent signal.

“This study bridges a major gap between predicting invasion success and predicting invasion impact,” Prof. Thakur explains. “We tested the leading ideas side-by-side and found that residence time outperforms classic predictors like latitude or simple trait proxies when it comes to explaining real ecosystem change.” The researchers’ analysis thus provides a new benchmark and will serve as a reference point for a worldwide community of scientists studying invasion impacts. “The Institute of Ecology and Evolution and the Institute of Plant Sciences both have long-standing expertise in biodiversity and invasion research, which provided a strong foundation for this project and allows the University of Bern to take a leading role in invasion biology”, Prof. Thakur notes.

What this means for biodiversity and climate action

The study’s message for conservation and policy is pragmatic: “Act early to prevent or remove invasive plants where native plant diversity is at stake – species losses accumulate with time”, says Prof. Thakur. For abiotic soil changes that tend to relax, use adaptive monitoring and targeted mitigation rather than one-size-fits-all interventions. “Managers shouldn’t assume that diverse communities or ‘usual suspect’ invader traits will safeguard ecosystem functioning once invasions take hold,” Prof. Xuhui Zhou of Northeast Forestry University adds. “Our results emphasize looking at how long invaders have been present and which ecosystem properties are most sensitive, while also considering the invader types.”

Because evidence remains sparse for animals and microbes, especially outside the Global North, the researchers call for long-term experiments and broader geographic coverage. Addressing these blind spots is crucial to building globally relevant invasion science. “Time is the underappreciated axis of invasion impact,” concludes Prof. Thakur. “We need to protect native diversity early and monitor patiently for soil changes that may stabilize over time. Recognizing this tempo can make invasion policy both more strategic – and more effective.”

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