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Species Introductions Accelerating

A study released this month has illustrated that the rate of species introductions to locations outside their native range is increasing faster than ever. Hanno Seebens and many others used the date of first records of introductions to plot the total number of new non-native species records every year since 1500. They show that this is not only increasing, but accelerating, with no signs of saturation. The increase was particularly marked since the 1800s. This global exchange of species is not good news, as although it increases species richness at the regional scale, globally the species richness of our planet declines as species go extinct.

Global temporal trends in first record rates (dots) for all species and taxonomic groups
Global temporal trends in first record rates (dots) for all species (a) and taxonomic groups (b–q) (Source: Nature Communications)

New Zealand was singled out as one country whose trend was negative compared to the rest of the world. As any traveller to New Zealand will have encountered, the biosecurity importation laws and policing are rigorous and every passenger is screened. In tandem with a ‘white-list’, where only certain non-native species are automatically permitted entry, and all others must be assessed, has clearly assisted in protecting New Zealand’s biodiversity and primary industries from the global trend in accelerating species introductions.

Treasure Islands campaign sign from Hauraki Gulf, New Zealand
Treasure Islands campaign sign from Hauraki Gulf, New Zealand (Courtesy Treasure Islands)

Coincidentally (or not) the majority of vertebrate species extinctions since 1500 have also been on islands, where invasive species (those alien species that go on to have negative impacts on biodiversity) are known to have an overall greater impact. Coinciding with our ability to eradicate some of these invasive mammals from islands, the rate of mammal introductions has actually slowed down in recent decades to the same level it was 100 years ago. This can give us some hope that learning from the past, implementing robust biosecurity, and enacting bold conservation interventions such as island eradications, can all counter the negative impacts of invasive species. An example of this published last month is the successful deployment of aerial distribution of baits for ant eradication. The implementation of aerial distribution of rodenticides was a step-change for rodent eradications in the 1990s and so it is very exciting to see it for ants.

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