Modelling shows pest plant habitat likely to increase
Environment Canterbury media release: 13th August 2024
Pest plants such as nassella tussock could become more widespread in future years, as Canterbury becomes warmer and drier.
While many of New Zealand’s invasive plant species are already in Canterbury, longer growing seasons and seeding periods, fewer frost days, and a more suitable habitat means they could eventually feature more heavily on our landscape.
Landowners should think about actions they can take now to help protect their assets down the track.
Weather changes increases pest habitat
During drought, the pasture opens up – creating more bare patches and enabling weeds to germinate seed come autumn. These pests then establish on those bare areas, outcompeting desirable pasture.
Some emerging species (both plants and animals) that have not been much of an issue in previous decades, including so-called ‘sleeper weeds’, may become a problem. We may see an increase in woodier species, like gorse and broom with seeds that live for longer or remain dormant in the soil, and other prolific seeders such as exotic grasses or herbaceous species.
In addition, pests currently contained in one local area might spread as conditions become favourable. For example, the ability for velvet leaf seed to germinate in soil currently stops somewhere around Mid to South Canterbury, but the line will likely move south.
Modelling looks at future climate
Scientific mapping we’ve commissioned - incorporating research from Dr Graeme Bourdȏt’s team at AgResearch - shows that far more land 60 years from now will be climatically suitable for both:
This modelling suggests that climatically suitable habitat for Chilean needle grass could increase by 60 per cent nationally by 2080 – with the bulk of that rise in Mid-Canterbury and South Canterbury.
Simply put, there’ll be more opportunity for these pests to invade land.
The extent of that invasion will largely depend on human activity. How the land is managed will heavily influence a weed’s ability to take hold in that environment.
This type of modelling is important as it allows farmers and biosecurity officers to know where to focus preventive measures, such as putting surveillance programmes in place.
Find out more about AgResearch's report on the potential spread of Chilean needle grass.
Preventing pest plants on rural properties
Sensible grazing management
Pest plants like nassella tussock and Chilean needle grass favour overgrazed, dry pastures. If land is overgrazed and then hit by drought, the seeds of these species, and of many other weeds, have a much greater chance of establishing new plants that facilitate local spread. Sensible grazing management helps keep weed pests at bay.
Minimise seed dispersal
Wider spread depends on the dispersal of seeds and other propagules and can occur in many ways. For example, seeds can be carried on machinery, on animals, in river gravel aggregate, with crop seeds, in flood water, and by people.
Preventative farm biosecurity practices include:
- Cleaning all vehicles before entry and after exit and cleaning clothing, boots, machinery, and other equipment after each use (chemicals may be required).
- Checking stock or hay before bringing it onto your property, including knowing where it came from and what the likelihood of pest-spread is.
- Educating contractors on good farm biosecurity practices.
Contact Environment Canterbury for pest advice
The team will put you in touch with someone who can provide advice and/or work with you to take measures to stop the pest(s) spreading further on your own property or onto others.