Are we ready for more weeds with a changing climate?

Posted by @mc_stanley1

Here in Auckland it appears that home owners want to pretend they’re always on that tropical holiday in Queensland. Aucklanders seem to have an unhealthy obsession with palm trees.

palm house

An example of an Auckland house with a tropical paradise & an exotic palm obsession

Unhealthy you say? Well, apart from the nasty injuries as a result of phoenix palm spines, I don’t mean unhealthy for people – but some introduced palms are certainly unhealthy for our native ecosystems.

The downside of wanting to retain that tropical holiday feeling around our houses, is that several introduced palms and other subtropical/tropical species have been planted in large numbers over the last decade, and several are showing signs of being ‘weedy’. The species we are most worried about are the ones that produce fruit that birds love eating and dispersing (think phoenix palm), and that are shade tolerant. Seedlings and saplings of shade tolerant species, such as bangalow palm, can germinate and grow inside native forest fragments, and can easily outcompete our native nikau palm.


A) Juvenile bangalow palm (Archontophoenix cunninghamiana) growing in an Auckland forest fragment. B) Bangalow and nikau seedlings growing side by side in a fragment – correct identification is difficult for community weeding groups.

While this spread is happening right now, we know that these subtropical/tropical species will be more successful and invasive in an increasingly warmer New Zealand – with the advance of climate change. Just a few less frosts per year is likely to mean that these species survive the winter and become more abundant and spread further south as conditions change.

So are we ready for this?

We don’t think so.

Christine Sheppard, Bruce Burns and I have recently written a ‘forum article’ in the New Zealand Journal of Ecology, where we raise this very issue. Despite knowing this will happen, and that we’ll have a whole lot more weeds to manage in the future, there’s not a great deal of tangible action. That’s because we currently have >400 environmental weeds we are already dealing with, and the thought of trying to pre-emptively manage more is frankly overwhelming.

There are things we can do though:

  • Include climate change in our current prediction and prioritisation processes, i.e. incorporate a ‘climate change factor’ into estimates of ‘predicted land infested’, and prioritise species likely to be weedy in our regions with fewer frosts and warmer temperatures;
  • improve funding streams for weed surveillance – so we can detect and manage these species before they take off and become unmanageable;
  • robust use of citizen science weed surveillance to increase NZ’s surveillance capacity;
  • raise awareness of the danger of increased ‘weediness’ under climate change and take a pre-emptive strike by educating the public about their plant choices and prevent invasion by banning high-risk species.


The last point is probably the most important. How can we change behaviour and have a conversation with the public about their plant choices? I don’t want to rain on anyone’s ‘tropical parade’, but really New Zealand, it’s time to wake up – leave those tropical paradises in the tropics and protect NZ.


Do we want those Aussie palms?

Yeah nah! No more palmsies for you.



Sheppard CS, Burns BR, Stanley MC. 2016. Future-proofing weed management for the effects of climate change: is New Zealand underestimating the risk of increased plant invasions? New Zealand Journal of Ecology 40:



me2smallDr Margaret Stanley is a Senior Lecturer in Ecology, School of Biological Sciences, University of Auckland and is the programme director of the Masters in Biosecurity and Conservation. Her interests in terrestrial community ecology are diverse, but can be grouped into three main research strands: urban ecology; invasion ecology; and plant-animal interactions.




Dr Christine Sheppard is a former member of the Ecology Ngātahi lab group, completing her PhD on the invasiveness of newly established alien plants under different climate change scenarios. She is now a postdoctoral fellow at the University of Hohenheim in Germany.


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