2.2 Energy Flow

"The Story of Spark: A Journey Through the Living Web"
A tale told by Energy herself

They call me Spark.

I was born in the heart of a star, millions of years ago. But this is the story of my latest journey—a much shorter one, but far more tangled and beautiful.

It began when I broke through the atmosphere and kissed the leaves of a young oak tree. My light, ancient and golden, was caught by chlorophyll in the chloroplasts of its broad green leaves. "Welcome," said the oak, and through photosynthesis, it transformed me into chemical energy, locking me inside a molecule of glucose.

"Time to grow," whispered the tree as it built itself with that glucose, stacking carbon into cellulose and storing some of me as biomass. That was my first transformation—light into sugar, energy into matter.

I waited in a leaf until one fine morning, a caterpillar came by. Munch. Gulp. I passed into its wriggling body, now part of a primary consumer. The caterpillar used cellular respiration to release me from the sugar. "Fuel!" it cried as I powered its movements. But not all of me made it. Some of me, as always, slipped away as heat—lost to the air, forever unrecoverable. That’s the second law of thermodynamics: I can’t be fully controlled.

Still, I journeyed on.

Before long, a robin swooped in. "Breakfast!" she chirped, and I was transformed again, moving up the food chain, from primary to secondary consumer. But with each step, I felt myself thinning—only a fraction of me made it through. Much was lost along the way as heat, undigested food, or waste. That’s why food chains are short. I can't climb too many steps before I’m mostly gone.

Then came the hawk.

It snatched the robin, graceful and fierce. Up another level. But only scraps of me survived that leap—barely 10% of what I was in the oak leaf. By now, my chemical form had shifted again and again, some of me stored in muscle, some in fat, some in heat that warmed feathers and vanished into wind.

The hawk eventually died. Its body was claimed by decomposers—mushrooms, bacteria, worms. They didn’t show up in neat food chains, but they mattered most of all. They broke down every last bit, releasing nutrients into the soil and letting matter cycle once more.

You see, I—Energy—flow through ecosystems in one direction, but Matter? She cycles. Always coming back around.

Now, I must tell you about something that disturbed me: Mercury. Not a noble metal, but a vile hitchhiker—non-biodegradable and sticky. It joined a droplet in the ocean and lodged itself inside a microplastic. A fish swallowed the plastic, and a larger fish ate that fish, and so it went—each step concentrating the poison. That’s biomagnification. Matter gone wrong. Some forms don’t belong in the cycle.

The more humans pollute, the harder it is for Matter to flow cleanly and for me to sustain life. Fossil fuel fires release me in chaotic bursts—yes, I’m energy still, but not where I’m needed. Deforestation chops down my old friends—the producers—and without them, I can’t enter the web at all.

Still, there is hope.

Every time a child plants a tree, every time someone protects a forest or restores a wetland, I find new ways in. Through photosynthesis, I’m reborn. Producers—algae, plants, even bacteria—let me in again, quietly rebuilding the foundation of the food web.

I am Spark. I travel from sun to leaf, from leaf to caterpillar, robin, hawk. I warm, I move, I build, I fade.

I cannot be created or destroyed. But how I’m used—that, my friends, is up to you.