I stare out the window of my writing studio, surrounded by trees, and my eyes slowly focus on the leaves. Oak leaves, birch leaves, popple leaves, the tubular needles of red pines and white pines and spruce. All the leaves.

Good Lord, there are thousands of them, millions perhaps, just in the viewing space framed by my window.

Each of these leaves is a quick change artist, recently emerged from its hiding place inside a bud. A month ago, staring out the same window, I would have seen only a skeletal framework of branches and twigs. Were I possessed of X-ray vision, I might have seen deeper, and glimpsed the stirring of sap inside the bones of the leafless forest.

Instead I saw only bark, the outer skin behind which the sap lies cradled.

So much lies hidden from view. I see the trunk and branches of a tree and think I am seeing the whole tree, but in fact I'm seeing only a part. Beneath the ground an entire root system lies buried, fated never to be sensed by anyone but voles and gophers and earthworms.

The realization prompts a pang of humility: Next time I think I am seeing the whole of another person, I'll try to remind myself of this. Below the surface of a fellow human much lies buried and unseeable, just like the roots of a tree.

My gaze returns to the leaves. A puff of breeze makes them twist and skitter, as if dancing to unheard music. Tethered by their stems to the twigs from which they've sprung, their range of movement is much less than ours, their position in the universe fixed to a space of mere inches.

But within that small space, amazing things occur.

From the first light of dawn to the end of the day, each leaf is busy making food. Unlike their counterparts in the animal kingdom, who essentially cannibalize other life forms, plants make food, and they do it as if by magic.

Using only sunlight, carbon dioxide and water, they manage to create organic compounds, the bread of life. Researchers claim the rate at which living beings die and consume each other is so high that they would all disappear from the earth within the lifetime of a human generation were it not for plants providing this re-formation of organic matter.

As if this weren't enough, in the process of photosynthesis each leaf imparts a small amount of oxygen into the air, which goes to form the breath of life. Without the relentless work of leaves, the rest of us would have nothing to eat or breathe.

Nor do their gifts stop here. In the act of making food and oxygen, leaves pump water into the air, drawn up from the roots of the tree and expelled from the underside of each leaf. It is estimated that a mature oak gives off as much as 200 gallons of water a day during the growing season; water which, in the oak tree's absence, would remain locked in the soil.

I close my eyes to give my mind a rest. The debt of gratitude we owe the leaves is staggering. Without them we simply could not exist.