Why Trees Matter

It was time for another class. I’d noticed, at the school competition, that the students loved the plays so much, they had a tendency to push over the barriers and crush the judges and photographers in their eagerness to get closer to the “stage.” So, as a review exercise, I divided the class into two groups and gave them 10 minutes to make up a play of the story of the Irish Potato Famine. I asked one group to depict the historical version, and the other to imagine that one of the solutions we’d discussed had worked and saved the day.

Without meaning to, I had put all the boys in one group and all the girls in the other. Duh. They were sitting in self-segregated groups in the classroom, but all I had noticed was, hmmm, here’s a convenient gap that seems to have equal numbers of kids on each side, that’ll do. What can I say? I was still pretty beat after my grueling trek, and not being very observant. The littlest things can tell you so much, if you bother to look.

The boys all ran off to play football (soccer) for 10 minutes. The girls huddled, assigned parts, shared ideas, rehearsed, and even asked a question or two to make sure they were getting the story right. I immediately tossed aside any regret I felt for my careless division of the class; the differences between the boys and the girls was so stark and enlightening to me, it was worth it!

Meanwhile, I drew a few diagrams on the blackboard that would help with the lesson to come.

We called the boys back in and I had them go first. As you might expect, I had to direct them, word by word, through a 2-minute recap of the story of the famine and the tragic ending. Then the girls presented their version, with the happy ending. They chose chemical intervention. Better living through chemistry! I used that as the segue to the lesson.

Remember? At the time of the famine in the mid-1800s, there were no effective chemical treatments. Even today, chemicals can’t cure everything, and they have many bad side-effects. What was the key problem that made it possible for this famine to occur? It takes a while, but I refuse to move on from this point until the students recall that a lack of diversity led to disaster.

Why do you need to eat? This question takes them by surprise.

To make us not hungry.

Yes, but what does your body do with the food? Farming is a lot of work. Why go to all that effort? They are looking at me with stunned expressions. (Sure, my questions are to engender interactive learning, but they are also my attempts to figure out what the students already know. Apparently, they haven’t yet learned a whole lot about nutrition or physiology.) To live and grow and be healthy, you need water, air, sunlight, and food, which contains nutrients that your body uses to make bones and muscles and skin and so on, and to create energy that lets you walk, run, work, and think. The nutrients in food are things like sugar, fat, protein, and minerals. When you eat food, your body takes those nutrients and turns them into you. I’m getting looks of amazement. Take bones, for example. Do you all have bones? Yes, they laugh. Bones are made mostly from calcium, which is a mineral. But where do your bones get calcium?

From rocks? More laughter. I’m pleased they’re making connections. Yes, rocks contain minerals, including calcium. But do you eat rocks? How do your bones get calcium?

From … food? Revelation.

Yes! So when you feel your tummy telling you, “I’m hungry!” really it’s sending you a message from your bones. “Get us some calcium! We need to grow!” And your muscles: “We want protein! And we need more energy! Burn some fat and sugar.”

Now, what about plants? What do they need to live and grow?

The children actually know more about farming than human health. Water, sunlight, air, soil.

And nutrients, too. They need the same things as we do. But do plants eat food the way we do? When you walk into your vegetable garden, do the plants say, “Time for dinner!” and grab you and eat you? No, they laugh. How do plants get nutrients?

Plants can do something animals can’t. They can make sugars, fats, and proteins from water, air, sunlight, and nutrients in the soil. (I’m editing as I go. There’s no way we can go into the miracle of photosynthesis and Krebs’ cycle.) The nutrients in the soil are minerals and elements that plants absorb through their roots. I turn to my visual aid on the blackboard: a tree, with trunk, branches, and leaves above ground, and a vast network of roots extending underground through layers of soil.

The roots of a tree often go as deep as the tree is tall, and as wide as the branches are long. The roots are very strong. Strong enough to break rocks. When it rains, the roots create a pathway for water to seep into the ground, where it is stored. The smaller roots are like a net that holds the soil and water in place. The water dissolves the minerals that are in the rocks deep under the ground. The roots absorb the water and the minerals, which are carried up into the trunk, to the branches, to the leaves, where they’re combined with air and sunlight to help the tree grow and produce flowers and fruit.

The branches of the tree are a nice place for bees to live, and they collect pollen from the flowers to make honey. The bees also fly from the trees to your garden, where they help pollinate the plants, which helps them produce more food for you. The branches are also a good place for birds to nest and roost. Those birds also visit your garden and eat a lot of the insects that may be harmful to your crops.

Eventually, the leaves die and fall to the ground, where they are broken down by insects, micro-organisms, and weather into a very rich soil called humus. I see signs of recognition. They know about humus. The plants in your garden, the ones you like to eat, love humus. Why do you think that is?

Because it is dark.

Humus is dark, but why is humus good for plants?

Because it is soft.

Yes, that’s one reason. Most vegetables have soft roots. They’re not like trees, their roots can’t split rock. They grow much better in softer soil.

Because it is moist.

Yes, humus holds water very well. And water dissolves the minerals and other elements that plants need. Remember? Plants need nutrients, just like us, and just like trees. So, the tree sends its roots deep into the earth, where it absorbs minerals and other nutrients. It uses the minerals to make leaves, flowers, and fruit. That’s what they’re made of. They die and fall to the ground (I’m embellishing my diagram like crazy. The tree blooms, sprouts, and fruits. Stuff piles up on the ground, under the canopy of branches), where they decompose into humus. (Edit, edit. No time for microbes.) That means the humus is full of the minerals and nutrients that the tree used to make the leaves. You see what has happened? The tree has taken minerals and nutrients from deep in the ground, and brought them to the surface, where they can be used by other plants. (I draw arrows in a loop, from the rocky substrate, into the roots and trunk and branches, to the falling leaves, down to the topsoil.) The tree and insects and microbes and weather are making beautiful, fertile, humus soil.

I can see that some, not all, of the students are intrigued. Some are not convinced. Sunday and the other teachers who were there, quietly in the background, look bemused.