Across the forest studies examined by researchers, there was no single agreed-upon way to tackle invasive alien plants, yet one pattern stood out: chemical treatment is still used more than any other option.
The review also found that the approach tied to the best reported results was biological control rather than the most common method.
What's happening?
Researchers headed by Lizzie Keen at Newcastle University's School of Natural and Environmental Sciences assessed published evidence on invasive alien plants in forests worldwide. As relayed by Phys.org, the review covered 192 studies from 26 countries and included 623 species-treatment combinations.
Working with the University of Stirling, the Newcastle team published the analysis in the Journal of Applied Ecology. Their survey showed a very large mix of management techniques in use internationally, but it did not identify any shared global best practice. Chemical control appeared most often overall.
When the authors compared results, biological control was associated with the most favorable outcomes. They also noted that timing and site conditions can change how well a treatment works, which complicates any attempt to prescribe a universal solution.
Why does it matter?
Invasive alien plants can crowd out native species, alter wildlife habitat, and make forests less resilient. As forests become less healthy, nearby communities can feel the effects through weakened biodiversity, disrupted recreation spaces, and reduced natural benefits such as cleaner air, water storage, and carbon capture.
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If managers continue to rely mainly on chemical-heavy approaches, progress toward the broader use of more sustainable forest management options could slow.
Another obstacle is cost transparency. The study found that labor and financial information is seldom reported in a consistent way, leaving land managers, public agencies, and communities with a weaker basis for comparing choices and using limited resources. If real-world costs remain unclear, scaling the most effective strategies becomes much harder.
What's being done?
The researchers said the evidence base still has major blind spots, including uneven research coverage around the world, a narrow focus on certain species, and inconsistent cost reporting. Filling those gaps could help foresters identify options that are both more effective and more affordable.
The study also strengthens the case for tailoring decisions to local circumstances. Because results can shift with the season and with site-specific conditions, forest managers may need to replace default treatments with plans matched to the invasive species, the landscape, and the timing of the work. That could improve results while also reducing unnecessary chemical use.
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Forest health depends as much on prevention as on cleanup. Gardening choices, cleaning hiking gear, and following local guidance on transporting firewood or plant material can help reduce the spread of invasive plants.
Those steps will not solve the global problem on their own, but they can ease pressure on already stretched land managers.
As governments and conservation groups invest in protecting forests, studies like this may help guide funding toward approaches that actually perform best on the ground while supporting a healthier future for ecosystems and nearby communities.
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