The first global register of alien species shows that a fifth of 6,400 plants and animals catalogued are causing harm. Some of the biggest factors in their spread are ballast water in ships for marine species and trade in ornamental plants on land, say scientists. The Global Register of Introduced and Invasive Species (GRIIS) provides the first country-wide checklists of introduced and invasive species.
They released data for 20 countries this week, with the aim of completing the register by the end of the year. Invasive species are living things that are not native to an ecosystem.
They can harm the environment, the economy, or human health. For instance, rats can cause bird extinctions on islands, while the crown-of-thorns star fish is smothering parts of the Great Barrier Reef.