Invasion Paradox: How Multiple Alien Plant Species Boost Ecosystem Function, But at a Cost

Mira Elwood in Climate & Environment April 2025 • 4 min read.

"New research reveals that while multispecies plant invasions can enhance ecosystem function, they also reduce variability, posing complex challenges for conservation and management."

The narrative around invasive species often paints a bleak picture—a relentless march of foreign organisms displacing native flora and fauna, disrupting ecosystems, and diminishing biodiversity. While this view holds considerable weight, the reality is often more complex and nuanced. Recent research has begun to uncover surprising facets of biological invasions, particularly when multiple alien species are involved.

Ecosystem functions, such as primary productivity and nutrient cycling, are fundamentally driven by the composition and biomass of plant communities. Traditionally, studies have focused on single alien species or contrasted invaded versus non-invaded communities to understand the impacts of invasion. However, natural environments are frequently subjected to invasions by multiple alien species simultaneously, leading to a more intricate web of ecological interactions.

A groundbreaking study by Chris M. McGrannachan and Melodie A. McGeoch sheds new light on this complex phenomenon. Their work, conducted in Victoria, Australia, examines how invasion by multiple alien plant species affects community-wide functional traits and the overall functional structure of understorey plant communities at the landscape level. The findings reveal a paradoxical situation: while multispecies invasion can increase certain aspects of ecosystem function, it also reduces the variability within the community, potentially making it more vulnerable to environmental changes.

The Dynamics of Multispecies Plant Invasion

The research was conducted in Chiltern-Mt. Pilot National Park in Victoria, Australia, a region characterized by a history of gold mining, forestry, and agriculture. These activities have significantly disturbed the native habitats, making them susceptible to invasion by various alien plant species. The study sites encompassed a range of relative alien cover, from approximately 3% to 61%, representing a gradient of multispecies invasion.

Balancing Function and Resilience in a Changing World

The findings of this study underscore the complex and often contradictory effects of multispecies plant invasions on ecosystem function and community structure. While the increase in functional diversity may initially seem beneficial, the reduction in variability could have long-term consequences for the resilience and stability of these ecosystems. Understanding these dynamics is crucial for developing effective conservation and management strategies that balance the need to enhance ecosystem function with the imperative to preserve biodiversity and promote ecological resilience in a rapidly changing world.