Why are weeds a problem in NZ?

Learning Outcomes:

• Students can give reasons why weeds can be a problem for economics (e.g. farming), our environment and our health.
• Students can discuss the different views people have about weeds.

Resources Required:

1. Weed Wipeout Instruction Card
2. Problems with weeds chart
3. Internet & computer access
4. Weedy Web Guide
5. Weedy Feelings
6. Weedy Views chart
7. Poisonous Plant poster

Activities:

Round One Match Up - Natives versus Weeds! Play the game 'Weed Wipeout' to help demonstrate the impact weeds have on native plants and explore the concepts of interdependence and biodiversity in the environment.

Reflect on and discuss how weeds can harm the environment e.g. smother, creep, climb.

Introduce the concept that weeds can also harm your health and economic activities, before moving to the research activity.

Research Activity

Aim: To find examples of the impact weeds have on the environment, our health and economics.

1. Set up three stations around the classroom, 1) Pest Plant Fact Sheets 2) Computers with Internet access plus the Weedy Web Guide 3) Poisonous Plants poster and fact sheets.
   
2. Split students into three groups to rotate through the stations to complete the 'Problems with Weeds' chart.
   
3. Collate students' findings using the sticky notes brainstorming technique to complete a class problem chart! Add to your Pool of Knowledge.
   
   Note: The Landcare Research website www.landcareresearch.co.nz has fabulous information related to the environment and economics, while the poisonous plants poster will be the most useful for investigating health concerns.

When is a weed not a weed?

Many people hold different views about weeds. The following activities are designed to show students that some weeds can have their place!

Role-play 'Weedy Feelings' to investigate the different views people have about weeds. Assign a card to small groups of 2-3 children. Give them time to practice their role then present each 'Weedy Feeling' back to the class.

Divide the class into two groups, for or against blackberry depending on the card they hold. Ask 'Are weeds a problem to everyone?' Let this discussion lead on to the next activity!

Researching Different Views:

There are plants that some people call weeds but others find useful.

Research the different viewpoints around pine trees, kiwifruit, privet and nodding thistle.

The Weedy Views chart lists different groups that have an interest and viewpoint about each plant. Select one or two groups from each column to investigate. What are their views about that particular plant? Do they have a use for that plant? Do they think that plant is a problem?

Explain your answers!

Note: www.botanical.com has great historical and medicinal information about weeds.

Extra Activities:

1. Invite a local farmer, gardener or horticulturist into your class to share their experiences with weeds. Students could create an interview sheet so they can find out the views the guest speaker has about weeds.
   
2. Newspaper Critique. Find three newspaper articles about weeds and weed control activities from papers in your area and identify some of the views different groups have about weeds by conducting a newspaper search. From the articles, put together a storyboard of people's views about weeds in your region.
   
3. Investigate the traditional uses of native plants by Maori, for example, herbal remedies, weaving and food. What impacts could weeds have on some of the traditional uses of these native plants?

Reflection:

• How can weeds be a problem in New Zealand ?
• Are weeds a problem to everyone?

Teachers' Notes:

Weeds are harmful for a number of reasons and can be classified as environmental, economic or health weeds.

Economic weeds are plants that are harmful to economic activities such as agriculture or forestry. They can replace crops and pasture grasses and cost New Zealand approximately $40 million in lost production, productivity or control costs.

Environmental weeds are plants that invade native bush, wetlands, streams and many other habitats with detrimental effects. Weeds can multiply quickly, replacing native plants and changing the habitat so it is no longer suitable for native animals. Weeds can form dense mats which smother seedlings and stop native plants from germinating. Vines can grow up and strangle or smother trees.

Aquatic weeds can clog up waterways and reduce food for our native fish.

Weeds can also be harmful to people's health causing skin rashes, allergies and hay fever. Some weeds are also poisonous.

Introduced plants and animals are the biggest threat to New Zealand 's biodiversity. Biodiversity is the number and variety of all life, plants, animals and micro-organisms, the genes they contain and the ecosystems they form. Biodiversity is important because it is essential to the ecosystem processes that make life possible.

In healthy ecosystems, plants, animals, micro-organisms and the physical world are in balance with each other. All plants, animals and micro-organisms live in a particular set of conditions (including physical, chemical and biological conditions) called a niche. Weeds can invade a niche of native plants and take their place. Some weeds are such aggressive competitors they can take over the niches of many plants. However, the plants they take over from may have fed insects, which in turn pollinated fruit that was then eaten by native birds.

These insects may not be able to eat the new weed plant, so they die or move away. This has a flow-on effect within the ecosystem, which is now out of balance, threatening other insects, plants and animals in a ripple effect.

See http://www.landcareresearch.co.nz/education/weeds/weedinfoa-2.asp for a great diagram demonstrating this concept!

Many people value our natural environment in the sense of cultural identity (traditional Maori uses of native plants for medicinal, craft and everyday uses), recreation (tramping, photography), tourism or economics (farming and horticulture). Each generation of people have the responsibility to act as kaitiaki (guardians) of our biodiversity and natural resources to ensure our country remains unique.

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