The impact of invasive alien species on threatened and endangered species: A geographic perspective

Abstract Invasive alien species (IAS) are one of the most serious threats to global biodiversity and one of the leading causes of federal protection required for native species under the United States Endangered Species Act (ESA). Our goal was to document how IAS impact threatened and endangered species (T&ES) under the ESA to improve recovery efforts. We reviewed Federal Register listing decisions for 1,545 T&ES listed under the ESA and found that 58% were impacted by IAS. Pacific Island T&ES (97%) face greater threats from IAS compared to Mainland (38%) and Atlantic Island T&ES (22%), but the number of IAS impacting T&ES has increased over time in all 3 geographic areas, except for animals on Atlantic Islands. On Pacific Islands, we found that IAS impacted T&ES most through adverse habitat modification and competition, mainly through invasive plants. Negative interactions caused by IAS on the Mainland were mainly from invasive fish and plants, while on the Atlantic Islands they were caused by invasive mammals and plants. The IAS causing the greatest number of negative interactions included rats ( Rattus ), wild pigs ( Sus ), goats ( Capra ), fish (e.g., Lepomis and Micropterus ), and various genera of plants (e.g., Schinus , Rubus , and Psidium ). Based on our findings, immediate actions are needed to protect native biodiversity in the U.S. from IAS, especially on Pacific Islands. Such management actions include eradication of IAS, restoration of native habitat, development of robust policies that aim to prevent the further spread and establishment of IAS, and effective decision support tools. These actions will require coordinated leadership to improve recovery of T&ES, especially given the synergistic impacts of international trade and climate change.