Invasive Alien Species on Islands

Invasive alien species are the major threat to islands by most metrics, and two open access papers published this week highlight this threat in different ways. In Nature Ecology and Evolution Wayne Dawson and colleagues identify global hotspots of alien species richness, and find islands and coastal continental areas are most strongly invaded. They also determine taxonomic group pairings which occur disproportionately often, such as birds with mammals, or vascular plants with spiders. New Zealand is identified as a particular hotspot for all possible combinations of taxonomic group pairings.

Hotspot and coldspot regions for cross-taxon established alien species richness (Source: Nature Ecology & Evolution)

Meanwhile, myself and colleagues from Island Conservation and the IUCN Invasive Species Specialist Group review invasive alien species on islands in Environmental Conservation. Analysing the distribution of invasive alien species on 33 small island developing states we found most invasive alien species are only on a few islands. However, we identify the 15 most widespread invasive alien species on islands. Most of these invasive alien species are plants, and outside of the tropical SIDS they are also widespread on other islands such as New Zealand. We also review the diverse impacts invasive alien species have on islands, and their interactions with other global change threats.

Leucaena leucocephalaWhite leadtreeTreeCentral America
Casuarina equisetifoliaIronwoodTreeSE Asia to Australia
Paratrechina longicornisLonghorn crazy antAntTropical Africa
Rattus rattusBlack ratRodentIndia to SE Asia
Adenanthera pavoninaRed bead treeTreeIndia to S China
Psidium guajavaCommon guavaTreeCentral America
Gliricidia sepiumQuick stickTreeCentral America
Kalanchoe pinnataAir plantHerbMadagascar
Tapinoma melanocephalumGhost antAntTropical Africa and Asia
Culex quinquefasciatusSouthern house mosquitoMosquitoTropical Americas
Cyanthillium cinereumLittle ironweedHerbTropical Africa and Asia
Jatropha curcasBarbados nutShrubCentral America
Mus musculusHouse mouseRodentCentral Asia
Oreochromis mossambicusTilapiaFishSouthern Africa
Portulaca oleraceaPurslaneHerbAfrica and Asia

Both studies highlight the factors which correlate with higher invasive and alien species richness on islands, namely gross domestic product (wealth), population size and density, and island area and coastline. Both studies also emphasise the important role biosecurity must play in slowing the rate of introductions, and eradications must play redressing the impacts of invasive alien species on islands.

Biosecurity for intercepting invasive alien species on islands
Biosecurity for intercepting invasive alien species on islands (Source: Environmental Conservation)

All these topics will be covered in depth at the Island Invasives conference being held in July 2017 in Scotland.

Read All Posts by James Russell


Meet the Author
Conservation biologist Dr. James Russell works throughout the world on remote islands and other sites to provide conservation solutions by applying a combination of scientific methods. Follow James on National Geographic voices for regular updates on his own work or other exciting developments in island conservation.