Weeds and native ecosystems – a context for learning

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.

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.

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.