How do invasive species alter ecosystem function?

Invasive species change how ecosystems work by interrupting long-established relationships among plants, animals, microbes, soils and disturbance regimes. Foundational ecological syntheses by Peter Vitousek at Stanford University characterize biological invasions as a component of human-driven global change that shifts nutrient flows and energy pathways. These shifts arise not only from the addition of a new species but from the novel interactions it creates with native communities and physical processes.

Mechanisms of change

Altered competition and predation are primary pathways. Exotic predators can reduce or extirpate naive prey populations, triggering trophic cascades that reconfigure community composition, a pattern emphasized by Daniel Simberloff at the University of Tennessee. Invasive plants commonly outcompete natives for light, water and soil resources and can change decomposition rates and nutrient availability; research by Peter Vitousek at Stanford University and colleagues links plant invasions to broad changes in nitrogen and carbon cycling. Some invaders hybridize with native species, diluting local adaptations and genetic distinctiveness, while pathogens carried by introduced hosts can cause novel disease outbreaks in naïve populations.

Physical habitat modification is another major mechanism. Aquatic invaders such as zebra mussels can radically alter water clarity and the distribution of nutrients, with effects on plankton communities and fisheries documented in studies by David Lodge at the University of Notre Dame. In semi-arid and Mediterranean climates, invasive grasses that produce continuous fine fuels have increased fire frequency and intensity; Paul D’Antonio at the University of California Davis has described how these grass–fire feedbacks convert shrubland ecosystems into grass-dominated states that are difficult to reverse.

Consequences for people and places

Ecological changes cascade into social, cultural and economic consequences. Loss of native species and habitat homogenization undermine ecosystem services such as pollination, water purification and fisheries, affecting livelihoods and food security. David Pimentel at Cornell University has drawn attention to the substantial economic costs associated with control and damage from invasive species. In Australia the cane toad, a case studied by Rick Shine at the University of Sydney, has had cultural and ecological impacts that complicate traditional hunting practices and harm native predators, illustrating how invasions intersect with Indigenous relationships to land.

Management and restoration are challenging because invasions often create new feedbacks that maintain altered states. Prevention and early detection are more effective and less costly than long-term control, a consensus echoed across reviews by scientists studying invasion ecology. Territorial differences in land use, governance capacity and cultural values influence which strategies are feasible; community-led monitoring and incorporation of traditional ecological knowledge can improve outcomes in many regions.

Understanding how invasive species alter ecosystem function requires integrating mechanistic ecology with social and policy context. Research by leading ecologists at institutions such as Stanford University, the University of Tennessee, the University of Notre Dame, the University of California Davis, Cornell University and the University of Sydney provides the evidence base for targeted interventions that reduce ecological harm while recognizing human and cultural stakes.