Opinion: Ecologist Sarah Flynn on the question of non-native plants

Opinion: Ecologist Sarah Flynn on the question of non-native plants Opinion: Ecologist Sarah Flynn on the question of non-native plants

Are we being too precious about native vs. exotic plantings?

For countries on the continental mainlands, stringent protection of ‘native species’ is something of a non-starter. After countless millennia of traipsing exotic discoveries from one end of the Silk Road to the other, most plants and animals have long since been assimilated.

Island nations like New Zealand and Australia are more rigorous when it comes to biosecurity. Nineteenth-century colonists looking to recreate the Old World in a new land brought over everything from roses to rabbits. Words like ‘biosphere’ and ‘eco-system’ weren’t part of the vocabulary.

Now, as we deal with the scourge of lupines-gone-mad and bird-killing possums running amok, ecological evangelists preach the gospel of native species appreciation. To some Kiwis, an Old English garden with climbing roses, violets, columbine and daisies is about as politically correct as walking down the street in a full-length mink coat.

A recent Stuff article asked: “Native plants: how much is too much?”.

The writer, Waikato-based farmer and sustainable living expert Sheryn Clothier, says that: “While I love the subtle variety in our bush, natives do not have stunning spring shows, interesting bark or autumn glory… ” and bemoans the fact that “Government policy seems totally biased. Subsidies and other incentives only apply to natives.”

Boffa Miskell ecologist Sarah Flynn responds to the article:

“While I don’t think that ‘natives are boring’ is a particularly good argument against using them (just use different ones – we have a LOT of beautiful plants), I can think of several ecological arguments in favour of retaining or planting exotic vegetation in some instances.

For example, some introduced trees get big really fast and can provide a much-needed ‘tall forest’ structure in a depleted landscape – these trees can even be used as part of a mixed native and exotic ecosystem to facilitate the regeneration of native forest.

Existing exotic trees shade streams and prevent soil erosion in much the same way that native species do, and while native vegetation is broadly considered ‘better for biodiversity’, exotic vegetation can be important habitat for indigenous flora and fauna. There are instances where the justification for ripping out well developed exotic vegetation in order to ‘restore’ with native plants may be pretty weak, and the biodiversity impacts of doing so are not well understood.

I also think we have an unreasonable fear of ‘weediness’ and a tendency to minimise the aesthetic and ecological values of exotic vegetation due to both cultural bias and based on a relatively small number of catastrophic examples of rogue invasive plants having really terrible environmental effects. To this extent, I agree that regulatory authorities can be unnecessarily inflexible about the use of exotic species in planting projects.

The key is to have realistic, site-specific objectives for any revegetation/ restoration project, and a clear-eyed understanding of the site’s existing ecological values and condition before you get started. For example, if your main concern is catchment soil stability and riparian buffering to enhance water quality (rather than indigenous forest restoration per se), and there’s limited existing native biodiversity in the area, there’s really no harm in incorporating exotic species. However, if your site adjoins an existing significant ecological feature, exotics probably aren’t appropriate as they could ultimately encroach into indigenous bush areas.”

For further information please contact Sarah Flynn

27 March 2018