Why do we need trees?

Andrew Smith

Royal Tasmanian Botanical Gardens, Queens Domain, Hobart, Tasmania 7000, Australia


The games demonstrated in this workshop attempted to explain the importance of plants. The session did not involve discussion about the uses of plants, but rather looked at why they are essential to all life on Earth. During sessions with children, time is usually spent discussing how we can all adjust our usage of plants for the sake of the health of the planet. The sessions also lead onto direct personal action, in the form of growing trees, and are used as a lead-up to the creation of conservation gardens in schools as part of the 'GreensC'ool' Program discussed in another paper presented at this Congress (Smith, 1998b).

Setting the scene

Lay everyone on the grass, with eyes closed. Hold on tight, because the planet we are on is presently speeding through space at about 110,000 km/h. It is also spinning like a top and the whole solar system we are in is turning slowly over and over. Every inch of space we travel through is a new one, we have never been there before. Luckily for us we take along a special supply of energy. The Sun. Sunlight powers all life on earth. But can you eat sunlight? Have a go – open your mouth and see if you can catch enough sunlight to chew. So how doe the Sun into energy. The plants. Imagine you are a leaf on a tree. Just uno catch the Sun, mix it with water and carbon dioxide and, hey presto, energy! So soak up that sunlight and make energy for you to grow.

Photosynthesis game

So what happens inside a leaf? You will need table tennis balls to represent molecules of H2,O,C,O2 and sunlight. These join together with velcro dots to make H2 0, CO2 and a sunlight ball (a number of each). What does a plant need for it to grow? Pass out the water, carbon dioxide and sunlight molecules. The plant mixes these ingredients to make sugar – CH2O. See if you can fit the molecules together to create a sugar molecule. It will only stick together if you include the sunlight ball (C+Sun+H2+O). The Sun's energy has been captured in the sugar molecule. But how do other living things, such as people, get hold of that energy? We eat it, we eat the plants. So we depend on plants for our food.

What is left over from photosynthesis? There should a number of O2 molecules left over. What is oxygen good for? Every living thing on the planet depends on the ability of plants to produce food and oxygen.

Lunch break

The aim: that children understand that they are individually dependent on plants for food.

Is it true that we depend on plants for food? Well, what did you have for lunch/dinner/breakfast? Did any of your food not come from plants? (Everything originates from plants because they are at the base of all foodchains.)

Living tree

The aim: that children understand that a tree is a living organism and how it works.

We are going to construct a tree using you as the parts. Choose the tallest and strongest person in the class. He/she is the HEARTWOOD of the tree. The heartwood is the strength of the tree, holding the tree upright but the heartwood of the tree is dead. (That is why a tree can be hollow and survive, although structurally weakened – only the dead heartwood is missing.) Around the heartwood is the area of the tree where all the action takes place – the sapwood. This is made up of two sections. The first one is the XYLEM. The xylem is where the water is drawn uxylem by joining hands to make a circle around the heartwood. The second part of the sapwood is called the PHLOEM. down the tree to feed the roots and branches. (The fact that there is sugar can be seen when a tree is injured and ts.) Choose five people to be the phloem by joining hands to make a circle around the xylem. What is on the outsidend diseases, a bit like a suit of armour. Choose eight people to be the bark by joining hands to make a circle arouned to lay on the ground with arms spread wide (and long hair fanned out as rootlets) to find the water needed to make the whole thing work.

This is how you make the tree live. The roots say "sluuuurp!" The xylem says "sluuuurp" and waves its hands in the air. The phloem gasps loudly (taking in carbon dioxide), says "aaah", and then sags at the knees. This has to be done in a synchronised way so that the tree sounds like this: "sluuuurp, sluuuurp, gasp, aaah!" Practise for a short time to make sure the tree is working. The two remaining children are INSECTS. Their job is to get to the heartwood of the tree within 5 seconds. If they manage it, the tree is dead. If the tree stops pumping then it is dead. (Choose sensible children to be insects, otherwise rough play will bring the lot crashing down.) Ready, set, go, 1. .. 2 .. 3 .... 4 ... 5, stop.

Other activities related to this are:

A patch of oxygen

The aim: that children understand that they are individually dependent on plants for oxygen. And that there is something they can do to stop the loss of trees.

One of the by-products of the tree's life is oxygen. How many trees do we need to produce enough oxygen for one person? An area of plants of about 625 square metres is required to supply sufficient oxygen for one person. If the trees continue to breathe, so does the person. That is a square 25 big steps by 25 big steps (25m x 25m). Step it out at a run, so that everyone is puffed out at the end. Stand in the centre. There is only enough oxygen in this square for one person. So, when I say, everyone has to hold their breath. I will touch one person at a time. When I touch you, you may take two deep breaths but you must then stop breathing again. Continue this until people are obviously no longer able to hold their breath. OK, everybody breathe! So how is it that we can all breathe? There are lots of trees in other places.

Discuss the importance of areas like the Amazon forests as oxygen suppliers. But every plant helps. Discuss the rates of deforestation around the world. Discuss how we all can adjust the things we do in every day life to reduce the amount of forests cut down. Ask for suggestions. Recycling, using less, planting trees. Follow up the session, at a later date, with another to grow a personal oxygen supply (i.e. trees).

The slishy sloshy swamp

The aim: that children understand that animals depend on plants as habitats. And even ugly places are important. And to protect animals we need to protect the places where they live and the other species in those places

Imagine the following place – the Slishy Sloshy Swamp. Tstretch into the sky for ovewamp to lay their eggs (the tree tops, because their venom causes instantaneous death.

Ask each child to design and draw an animal that is capable of living in the swamp. It can have any feature you wish to give it as long as there is a reason for it. It needs some way to eat (hollow fangs to suck the eggs perhaps), protection from its enemies (a shell or spines or a horrible smell), a means of moving around on the mud (big flat feet) and a way of finding its way around in the dark (big eyes and ears, whiskers, sonar, luminous nose) and so on. Compare imaginary animals.

Compare imaginary adaptations with those of real animals. Write a news-article about your amazing animal.

Invent a threat, e.g. someone is going to pump out the orange mud to sell as undercoat paint. What will happen to the swamp if the mud is pumped out? The trees die – so no more shade for the animal, the mud is gone – so no more eggs for the animal to eat. The animap National Park.

Write articles for the Slishy Sloshy News explaining the need to protect the swamp. Write articles explaining the value of "developing" the swamp's resources. Conduct a debate between the opposing sides. Look for sustainable methods of development which do not degrade the swamp's ecological value.

What about if someone came in and cut half the trees down? The shelter is gone and half of the swamp is of no use to the animals. How do you repair the damage? By growing more trees from seeds collected from the trees in the swamp (i.e. a recovery plan working with your local botanic garden).

Is there a Slishy Sloshy Swamp near you requiring your help? What lived in your neighborhood before it became a city/town. How can you go about repairing the damage? Create a Greencare/GreensC'ool group to grow and plant local plant species in the school grounds.

References and inspirations

Briggs, J.D. and Leigh, J.H. (1988). Rare or threatened Australian plants. Australian National Parks and Wildlife Service.

Cornell, Joseph B. Sharing nature with children.

Corson, Walter H. (1990). The global ecology handbook, what you can do about the environmental crisis . The Global Tomorrow Coalition, Beacon Press.

Department of Arts, Sports, Environment, Tourism and Territories (1992). Australian National Biodiversity Draft Strategy .

Smith, Andrew (1989). Leaf Walk—Plant adaptations. (Teachers kit) Royal Tasmanian Botanical Gardens, Hobart, Australia.

Smith, Andrew (1991). From Small Seeds ... a green world grows, Royal Tasmanian Botanical Gardens and the Australian Early Childhood Association.

Smith, Andrew, (1990). The amazing sun powered food factory. (Teachers booklet). Royal Tasmanian Botanic Gardens

Van Matre, Steve (1979). Sunship Earth. Institute of Earth Education, American Camping Association.

Young, M.D., Cocks, C.D., Humphries, S.E. (1988). Australia's Environment and its Natural Resources. CSIRO Australia, Institute of Natural Resources and Environment.


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