Marsh

She explained the cycle, because "decomposition" sounds like an ending and it's really a beginning.

"Watch what happens to a dead reed," Marsh said. "It falls into the shallow water. Bacteria and fungi — the decomposers — go to work, breaking its body back into the raw nutrients it was built from: nitrogen, phosphorus, carbon. Those nutrients dissolve into the water and soil, where new plants take them up and grow. Insects eat the plants, fish eat the insects, herons eat the fish — and when they die, they fall back into the water and the whole thing starts again. The dead reed didn't leave the system. It just changed jobs, from 'plant' to 'fertilizer' to 'part of a new plant.' In here, death is a doorway, not an exit."

The subtext the older students heard was about waste and value — that in a well-made system there is no such thing as garbage, only material waiting to become the next useful thing, and that what looks like an ending is often a hand-off.

Marsh set the record straight on her reputation, because it cost the world dearly.

"For centuries people called wetlands worthless and drained them — for farms, for cities — thinking they were reclaiming useless swamp," she said. "Then science caught up. Marshes filter pollutants out of water for free, cleaner than any treatment plant. They soak up floods like a sponge, protecting everything downstream. They store enormous amounts of carbon in their waterlogged soil. They're nurseries for a huge share of the fish people eat. We destroyed half the world's wetlands before realizing we'd been bulldozing some of the most valuable land on Earth because it didn't look valuable."

The heron asked why the marsh recycles so much better than dry land.

"Water and slowness," Marsh said. "The waterlogged soil holds everything close — nothing blows away or washes off fast — so the decomposers have time to break it all down and hand it back. Dry land loses nutrients; a marsh keeps them, circulating the same material around and around. That patience, that refusal to let anything escape the cycle, is exactly what makes me look like stagnant muck to a passer-by and makes me, in truth, the richest ground there is."