How do invasive species threaten native plants and animals?

Invasive species threaten native plants and animals by disrupting the ecosystems they colonize, often leading to a decline in biodiversity and, in severe cases, the extinction of native species.12

These threats typically manifest through several ecological mechanisms:

• Predation: Invasive predators, such as the brown tree snake on Guam or feral cats on islands, can be highly efficient at hunting native species that lack evolutionary defenses, leading to rapid population declines.134
• Competition: Invasive species often outcompete native organisms for essential resources like food, water, and living space. For example, the common buckthorn creates dense vegetation that blocks sunlight, displacing native plants.12
• Disease Transmission: Invasive plants and animals can act as vectors for parasites and pathogens, introducing illnesses to native populations that have no natural resistance.13
• Hybridization: The introduction of nonnative species can lead to interbreeding with rare native species, effectively "swamping" the native gene pool and threatening their genetic integrity.4
• Habitat Alteration: Some invasive species physically transform their environment, such as European wild rabbits in Australia, which degrade grazing lands by consuming native vegetation and stripping bark from trees.3