This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
NOAA's own definition of a wetland is almost plain to the point of being unhelpful: an area of land that is saturated with water. What that saturation does, once it is sitting there, is the more interesting story. NOAA describes wetlands acting as water filters, absorbing excess nutrients, sediments and other pollutants before they ever reach a river, a lake or the open sea. The same soaked ground works the opposite direction during a storm. Rather than letting a heavy rain run straight off the land, a wetland absorbs and slows the floodwater, which NOAA credits with alleviating property damage and, in the worst events, saving lives. Two jobs, filtration and flood storage, done by the same passive, unpowered structure of soil, roots and standing water. This atlas classifies Wetlands as its own biome rather than folding it into Freshwater, because a wetland is not defined by a climate band the way a rainforest or a desert is. It is defined by hydrology, and NOAA's own classification proves the point: marine wetlands sit on open coasts, estuarine wetlands where a river meets the tide, riverine wetlands beside rivers, lacustrine wetlands fringing lakes, and palustrine wetlands, the marshes, swamps, fens and bogs most people picture first. A wetland can appear inside a tropical rainforest, on an arctic coast or in the middle of a desert wherever water lingers, which is exactly why it needed a category of its own.