Alien invaders – Where should we focus?


If you only read the title of this post, you may have thought it was referring to the green men from the show X-FILES or maybe you envisioned invasion by human immigrants making Donald Trump pull out his luxurious locks .

However, it is not the extra-terrestrials or human immigrants I am referring to but the invasive species that are costing us billions of dollars, the ones that we have helped cross our borders, the vines, mosquitoes, ants and the like that now thrive in a novel environment.


Megalopyge albicolis (a butterfly, pictured here as a caterpillar)-although not currently deemed an invasive species, I’d say it would be on some peoples ‘unwanted species list’ based on the resemblance to Mr Trump’s hair. Image by Andreas Kay (CC BY-NC-SA 2.0).

While we should be concerned about non-native species, we need to remember that some actually contribute positively to the environment and people’s every-day lives. The first example that comes to mind are those non-native species deliberately introduced to control pests to appropriate levels, commonly referred to as biocontrol agents.

The non-native species we should worry about are those that displace our native species, undermine ecological services, negatively affect the economy and threaten human health. It is these species that begin to be recognised as ‘invasive’ (the term for a non-native species causing undesirable effects) by fellow humans.

New Zealand is home to thousands of non-native species. In fact we have hundreds just from one order of insects (see Darren’s blog post).  This is coupled with growing costs of control and mitigation.  The fact is we cannot control all non-native species.  Therefore, management should use a prioritisation approach, such as managing invasive species likely to have the greatest impacts on native biodiversity.

argentine ant

Argentine ants have invaded parts of New Zealand and are recognised as one of the world’s worst invasive species by the World Conservation Union.  Image by Pedro Moura Pinheiro (CC BY-NC-SA 2.0)

I know what you’re thinking Mr Trump, but we can’t make them pay for their own control and building a wall isn’t going to solve the issues already in the country.

This is why as part of my Masters project I am creating an alternative method to assess the risk of non-native species. It is proposed to be used as a tool for management prioritisation for those species most negatively competing with our native species, as well improving our standards on importing and releasing biocontrol agents into New Zealand.

zzzZane McGrath is an MSc student in the Centre of Biodiversity and Biosecurity, School of Biological Sciences, University of Auckland. He is supervised by Darren Ward, Graham Walker and Frances MacDonald (Plant and Food Research, Auckland) examining parasitism by exotic species in native environments.

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