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  • Introduced plant species – friend or foe? This might depend on who is answering the question. Over 25,000 exotic plants have been introduced to Aotearoa New Zealand. Some of these are highly valued for primary production as food and export crops, while others are carefully tended in home gardens.

    The difference between an invited and an uninvited plant – a prized specimen and a weed – is entirely circumstantial. One person’s treasure is another person’s weed.

    Rt Hon Simon Upton, Parliamentary Commissioner for the Environment

    Nearly 3,000 introduced plant species currently grow in the wild in New Zealand. For comparison, there are about 2,300 plants native to Aotearoa, and only 31 introduced land mammals have been able to survive and thrive in the wild. Exotic weeds pose significant threats to our native ecosystems.

    Rights: Parliamentary Commissioner for the Environment

    Weeds that threaten native ecosystems – slideshow

    A slideshow of weeds and the adaptations that make them problematic in a New Zealand setting.

    Use the Slideshow menu for further options, including view full screen, and go here for the download option.


    This context for learning makes use of resources developed in response to the Parliamentary Commissioner for the Environment’s report Space invaders: A review of how New Zealand manages weeds that threaten native ecosystems and the Hub articles Weeds – threats to native ecosystems and Tackling weeds to safeguard native ecosystems.

    As a topic, invasive plant species have the potential to combine conceptual scientific understanding, cultural awareness and thinking about socio-scientific issues.

    Curriculum links and key science concepts

    Learning about weeds and their impacts on native ecosystems covers Living World concepts associated with ecology and evolution.

    Key science concepts could include:

    • living things are suited to particular habitats
    • living things respond to environmental changes
    • invasive species may have adaptations that allow them to outcompete native species
    • invasive species may spread more easily because of their effective methods of reproduction
    • plants can be grouped/classified in different ways
    • classification involves careful observation and comparison.

    Nature of science concepts could include:

    • understanding the breadth of the problems and coming up with solutions requires extensive collaboration between the science communities and regulatory bodies
    • societal and cultural elements influence and prioritise the targeting of specific weed species
    • environmental monitoring is needed to gather and interpret data and to inform action
    • some problems are bigger than science can solve.

    Science capabilities could include:

    • gather and interpret data by surveying plants on school or local properties
    • use evidence from databases to identify weeds/invasive species of particular concern
    • interpret representations and diagrams
    • engage with science by taking action to remove weeds and/or restore areas of native ecosystems.
    Rights: Parliamentary Commissioner for the Environment

    Management approaches and the invasion curve

    A guideline that links management approaches to an exotic plant's position along the invasion curve. The invasion curve is in essence a graph of species invasion from non-existent (absent) to being widespread.

    Multiple pathways for learning

    The broad context of exotic plant species and threats to native ecosystems provides opportunities for cross-curricular learning. The challenges associated with defining which plants are weeds and whether and/or how to manage them incorporates social, cultural and ethical considerations.

    Mātauranga Māori concepts could include:

    • the impacts of invasive species on the mauri of the location
    • invasive species cause disruptions to the natural balance of Papatūānuku
    • any plant cover is more acceptable than bare ground, which is viewed as a scar on Papatūānuku.

    These concepts are more comprehensively explained in prominent rongoā Māori practitioner Rob McGowan's report prepared for the Parliamentary Commissioner for the Environment, Mauri tū! Mauri ora! Māori perspectives on exotic plants in Aotearoa.

    Socio-scientific concepts could include:

    • plants can be both wanted and unwanted in different settings
    • who decides what constitutes weed plants and who is responsible for their control and/or removal
    • the use of toxins in weed removal
    • the use of introduced species for biocontrol of invasive plants
    • prioritising particular plants and/or particular locations for eradication and restoration.

    Approaching this topic with a socio-scientific lens builds students’ understanding of the science concepts and can help to develop their argumentation, critical thinking and decision-making skills.

    Teaching ideas

    Pages 33–39 of the report includes three case studies:

    • Wilding conifers – a burning issue.
    • Russell lupins – a beautiful threat to native ecosystems.
    • Gorse – a thorny matter.

    Each case study includes different perspectives on plant species and their management.

    • Encourage students to list the pros and cons of the particular species.
    • Pose provocative statements – positive and negative – for students to research and defend.
    • Use local curriculum principles to create similar case studies concerning local plant species of interest.

    Related content

    The Connected article The war on weeds explains how students use digital technology to help combat the spread of weeds.

    Exotic plant species can increase the risk of wildfires.

    Biocontrol is the use of one organism to control the numbers of another. Find out how it is used to control the weeds:

    Invasive plant species are often hard to control due to their effective methods of reproduction. Learn more about:

    The article Teaching ethics explores ethical discussions and strategies for teaching ethics and curates Hub resources on the topic.

    Activity ideas

    In the activity Threats to biodiversity, students research three aspects of biodiversity loss – direct species loss, habitat loss and pests and weeds.

    Adapt this DIY plant classification activity to focus on welcome and unwelcome plants in the school or local environment.

    Useful links

    Visit the Parliamentary Commissioner for the Environment website.

    Manaaki Whenua – Landcare Research has an online key for the identification of weeds in New Zealand, which is illustrated with more than 10,000 images.

    Weedbusters NZ has an extensive weed list with images and downloadable information sheets.

    This New Zealand Geographic article tells the stories of some passionate people weedbusting in their local areas.


    This resource has been created from Space invaders: A review of how New Zealand manages weeds that threaten native ecosystems and associated resources (including this FAQ and Mauri ora! Māori perspectives on exotic plants in Aotearoa – Robert McGowan) with support from the office of the Parliamentary Commissioner for the Environment.

    Rights: Parliamentary Commissioner for the Environment

    Parliamentary Commissioner for the Environment logo

    The Parliamentary Commissioner for the Environment is one of three Officers of Parliament that work in an independent watchdog capacity, helping Parliament hold to account the government of the day.

      Published 7 June 2023 Referencing Hub articles
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