A meta-study published by Frontiers in Ecology and the Environment explores alien species as drivers of recent extinctions. Species moved from their origin to a new location--primarily by humans--is the #1 cause of extinction.
Of the 935 total recent extinctions in our dataset, 261 of 782 animal species (33.4%) and 39 of 153 plant species (25.5%) had aliens listed as one of the extinction drivers (Figure 1). Alien species ranked first as a driver of animal extinctions, well ahead of the second-ranked driver, biological resource use (ie hunting and harvesting), with 18.8% of species affected. Aliens also ranked first for plant extinctions, slightly ahead of biological resource use (a driver in 23.5% of plant extinctions) and agriculture (19.6%). In contrast, only 2.7% of animal extinctions (21 species; rank 8th) and 4.6% of plant extinctions (seven species; rank 7th) had native species listed as one of the extinction drivers.