The wooden boardwalk creaks under our feet as we step out onto it, swaying over the marsh like the deck of a boat. Wind catches the bushes, the trees, the grasses almost taller than I am, sending them billowing across the waters, the sails of living ships on a hidden sea.

Signs along the boardwalk tell stories of the marsh, of its purpose. It's a natural filter of sorts, cleaning the waters of the surroundings in a gentler and more effective way than anything humanity could invent. Nigh on a hundred different species of animals live here, sheltered beneath the plants, thriving in this preserved cleanser of nature. This marsh has been here longer than any of us, and if it is maintained and cared well for, it will outlast us and our faults, too.

I glance down over the edge of the boards from time to time, taking in the colors of the water. In some places, it's cool and pure, as clear as the sunlit sky above; in some, seeds speckle the surface like stars; and in others, the surface is slick and half-stained with oil. Beneath the waters, though, the peat is deep reddish brown, the color of lives being recycled and reused for good even after death. One of the signs claims that the peat reaches three or four feet beneath the water, composed of layers and layers of decomposing plant matter - seeing how tall the grasses grow here, I wouldn't be surprised if it reached deeper still.

There's a fairly well-known theory regarding the answer to the Fermi paradox, which poses the question of why we haven't encountered another alien civilization if space is so vast. This solution, known as the Great Filter, considers the possibility of every sapient species being forced to face a massive crisis before being able to break through the great expanses of space and hear the calls of others. With all that has been happening in the world, plague and collapse and climate change and the accumulating consequences of our reckless advancement, I wonder if that Filter may hit us soon. Decide whether we are oil or seeds or water, and carry us away as it sees fit.

As I muse on this potential destiny, a flicker of movement catches my eye, and I turn in time to watch blue-grey wings open and catch the breeze. Far across the marsh, a heron takes flight, coasting in a slow loop around us. It's as though the world goes silent for a long, long moment, still and quiet with awe, until it glides away to parts unknown.

With a newfound smile on my face, I continue to walk, matching my paces to the sway of the deck as we sail ever onward. The earth provides more than humanity would guess, locked in pillars of metal and glass. This natural filter was not meant to clean me, but walking down the boards, I am renewed nonetheless.