(1) Near important ports and ports, on both sides of railways and highways. Alien species introduced by international freight often "land" near ports and ports first, and then start to spread after meeting suitable environmental conditions to establish small populations. Alien species carried by trains and cars are easy to settle and spread on both sides of railways and highways.

(2) Forests and grasslands with serious human disturbance. Forest and grassland ecosystems were originally stable, and serious human disturbance such as deforestation and overgrazing degraded the ecosystem and reduced its diversity, creating favorable conditions for the invasion of alien species.

(3) Islands, waters and pastures with low species diversity and simple habitats. Species diversity is low, natural inhibition is poor, the number of natural enemies is small, exotic species are easy to survive, and the population is easy to expand.

(4) Habitat destroyed by sudden natural disturbance (such as fire and flood). In these habitats, the ecosystem has been seriously damaged in a short time, and the species composition and community structure have become simple, and invasive species can easily occupy a large number of niches and become dominant species.