Biological invasion

Biological invasion is the establishment and spread of a species beyond its native range. It can alter ecosystems, economies, and human health.

Invasion pathway: A sequence of human or natural processes that moves organisms beyond their native range. Pathways explain how organisms reach new regions before establishment.
Non-native species: A species occurring outside the geographic range it occupies naturally, usually because of human activity. Non-native status describes range history, not whether a species spreads or causes harm.
Biosecurity: Policies and practices that reduce the movement and establishment of harmful organisms. Border checks and other safeguards target introductions before they become invasions.
Island biogeography: The study of how island area, isolation, immigration, and extinction shape species richness. Islands can be especially vulnerable when introduced predators or competitors encounter isolated communities.
Cane toad in Australia: The spread of the toxic cane toad across Australia after its introduction in 1935. It illustrates how a biological-control introduction can become a widespread ecological problem.
Propagule pressure: The number and frequency of individuals introduced to a new region. Repeated, numerous introductions raise the chance that a population will establish.
Naturalization (biology): The establishment of a self-sustaining population of a non-native species. Naturalization marks the transition from arrival to persistent presence.
Early detection and rapid response: A management approach that finds new biological invasions quickly and acts before they spread widely. Fast action can be more feasible than controlling a widespread invader.
Extinction: The permanent loss of a species when its last living individual dies. Introduced predators, competitors, and pathogens can contribute to native species extinctions.
Brown tree snake in Guam: The establishment of the brown tree snake on Guam, where it devastated native bird populations. This invasion shows how a predator can drive severe losses among island wildlife.

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