Alien invaders are the second biggest cause of species extinctions, according to a new study, but not everyone is convinced.
The role invaders play in wiping out native species has long been a bone of contention for conservationists.
The new study looks at the Red List, a catalogue of extinct and threatened species drawn up by the International Union for Conservation of Nature (IUCN). For species that are completely extinct or extinct in the wild, those who draw up the list identify one or more contributing factors.
Last updated on 18 February 2016