A growing dominance of fast-growing tree species is reshaping forests worldwide, potentially weakening ecosystem stability, biodiversity and long-term carbon storage, according to a major new global study.
The findings come from a study titled “Global functional shifts in trees driven by alien naturalization and native extinction,” published in the journal Nature Plants. The research is based on an analysis of functional traits and environmental niches of 31,001 tree species across the world, making it one of the most comprehensive assessments of global tree diversity to date.
As reported by Phys.org, the study examines how two simultaneous, human-driven processes, extinction of native tree species and the spread of alien or naturalised species are transforming forest composition and ecological functioning. By comparing naturalised, threatened, and non-threatened species, the researchers assessed present trends and projected how forests are likely to change under increasing climate stress, land-use pressure and disturbance.
The analysis suggests that future forests will increasingly be dominated by fast-growing, high-resource-use species. These trees typically have light leaves, low wood density and rapid growth rates, allowing them to establish quickly in disturbed environments. In contrast, slow-growing species with dense wood, thick leaves and long lifespans face a higher risk of decline and extinction.
While average trait values across species groups do not differ dramatically, the study identifies clear ecological patterns. Naturalised species occupy broader functional and environmental spaces and tend to thrive in colder and more climatically variable regions. Threatened species are generally more specialised, associated with warm, stable, and nutrient-rich environments, while non-threatened species show intermediate characteristics.
The researchers warn that these shifts could have lasting ecological consequences. Although the spread of naturalised species may temporarily increase local functional diversity, their fast-growing, acquisitive strategies could reduce long-term ecosystem stability. In contrast, native extinctions lead to pronounced losses in functional and environmental trait space, particularly in regions exposed to high climatic variability.
Trees play a central role in regulating Earth’s climate and ecosystems. They store carbon dioxide, provide habitats for wildlife, stabilize soils, regulate water cycles, and support human livelihoods. The study, however, indicates that forests are entering a phase of increasing homogenisation, with fewer functional strategies represented across landscapes.
Slow-growing tree species are identified as especially vulnerable. Many of these species occur naturally in limited geographic ranges, particularly in tropical and subtropical regions where biodiversity is high and ecosystems are tightly interconnected. Their loss can leave ecological gaps that fast-growing alien species rarely fill, even when those species become widespread.
Fast-growing trees such as certain acacia, eucalyptus, poplar, and pine species are projected to become more prominent. While these trees are often favoured for timber and biomass production due to their rapid growth, they are generally more susceptible to drought, storms, pests and climatic shocks, making forests less resilient over time.