Efforts to manage invasive alien plant species in forests could be held back by a continued reliance on chemical methods, according to a new study.
Research led by Lizzie Keen, a postgraduate researcher at Newcastle University's School of Natural and Environmental Sciences, shows that chemical methods remain the dominant approach worldwide, despite growing recognition of the need for more sustainable management options.
The findings show widespread issues driven by how countries approach, tackle and report invasive alien plants (IAPs), also referred to as invasive non-native plant species, affecting their success at reaching global targets for biodiversity and forest health.
Forests are critical to the provision of goods and services. They face many threats including the presence of IAPs which can impact native biodiversity and ecosystem functioning.
However, there are data gaps around outcomes of managing IAPs in forests. To help fill this knowledge gap, the authors analysed existing studies into the management of IAPs, spanning 26 countries and covering 192 studies with 623 combinations of species and management treatments.
The results highlight the extraordinary number of management treatments used to tackle the issue of IAP species globally, yet there is still no consensus on the most effective management strategy. However, the findings confirm that the use of chemicals is the most popular global approach to address IAPs, although biological control had the most positive management outcomes.
In addition, the findings highlight that season and site-specific conditions are important for influencing the outcome of management. The study also shows that few organisations report on the labour and financial costs involved in dealing with IAPs.
Published in the Journal of Applied Ecology , the study was led by Newcastle University and the University of Stirling with funding by Natural Environment Research Council (NERC) and the Woodland Trust.
Lead author, Lizzie Keen, said: "Our study exposes urgent and critical knowledge gaps in forest IAP management, which need addressing to meet global targets for biodiversity and forest health. These gaps include highly uneven global research effort, narrow species focus, limited method replication, overlooked seasonal effects, and inconsistent cost reporting.
"A strong legacy of using chemical methods may also be deterring efforts to develop non-chemical approaches. Immediate action is needed to develop standardized methodologies and reporting channels to close these gaps and thus aid informed choice of management options by practitioners."
Principal Investigator Dr Zarah Pattison, Senior Lecturer in Plant Sciences at the University of Stirling, said: "Non-native plants are invading forests worldwide, yet we still don't know the best ways to manage them.
"Our review reveals alarming gaps in research, patchy global coverage, and a heavy reliance on chemical controls.
"Where management is taking place, we implore land managers and researchers to record key information on costs, area treated and labour time and wherever possible, the change in invasive alien plant populations following treatment, so that we can more effectively assess management outcomes."
Dr Harriet Downey, Conservation Evidence Manager, Woodland Trust, added: "Invasive non-native plants put the benefits of our UK ancient woodlands at risk. Based on current evidence, it is difficult for land managers to make effective decisions on removing widespread non-native species in the most sustainable, cost-efficient, and permanent way. We must identify best conservation practice in the removal of invasive non-native plants from our woodlands, to ensure we can restore woods and trees to their full potential, so they can thrive for people and wildlife, and deliver nature recovery on the ground."
The authors recommend future research that focuses on greater collaboration with practitioners and more standardised data reporting which will be key to strengthening global management efforts and their effectiveness.
Reference
Keen L, et al. Management of invasive alien plants in forests: a global perspective. Journal of Applied Ecology. Published online July 7, 2026. doi:10.1111/1365-2664.70451
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