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Chicago Nature Glossary

alien species: any plant or animal species that does not have an evolutionary history in its current location.

biodiversity: the biological variety of plants, animals, and other organisms. Greater biodiversity leads to healthier ecosystems.

Chicago: Here’s the short version: In the late 1600s, Potawatomi Indians who traveled the area rivers were commonly heard to yell “Chicagoua!” after catching a strong whiff of chicagoua, or wild leek, growing prolifically along the wooded banks. Wild leek is part of the onion family, hence the Chicago nickname, “The Big Onion.”

closed wetland: a wetland with a closed system where there is little to no exchange of water, sediment, nutrients, pollution, organisms, and energy with surrounding area. Generally, closed wetlands are fed by precipitation or groundwater. If groundwater is a source, the wetland’s chemistry and water level can be affected by groundwater contamination and land-disturbing activities within the watershed.

dolomite prairie: a rare kind of prairie that makes its home upon a bed of porous limestone called “dolomite.” Under these hard conditions, growth and propagation are stunted compared to tallgrass prairie.

dune and swale: See “ridge and swale.”

ecological restoration: the activity of assisting in the recovery of ecosystems that have been damaged by unsustainable or damaging activities and reestablishing them as viable habitats, with the goal of increasing biodiversity and restoring ecological balance for the benefit of all life.

fen (aka calcareous fen): a rare wetland habitat fed by mineral-rich groundwater of generally alkaline pH that passes through deposits of gravel left behind by Ice Age glaciers. The water seeps up to the surface over a wide area and flows out, leaving a soggy gravel bed where a unique community of plants flourishes in the fen’s unique chemistry.

forb: a flowering plant with leaves and stems that is not a grass, sedge, or rush and that, unlike woody plants, dies back at the end of each growing season.

forest: a plant community with a dense tree canopy that blocks over 80 percent of the light from reaching the ground.

inflorescence: a group or cluster of flowers arranged on a stem.

invasive species: any native or nonnative plant or animal species that moves into a habitat with adverse effect.

kame: a mound or ridge of gravel and sand deposited by water derived from melting glaciers.

oak savanna: in the Midwest, a habitat consisting primarily of grasses and wildflowers under widely spaced oak trees with a park-like open canopy. Tree canopy coverage ranges from 10 to 50 percent. Oaks dominate, but hickory, elm, plum, hazelnut, and others may also be present. Bur oaks are found in black soil (or tallgrass) savannas along with northern pin oaks, whereas black oaks are the principal trees of sand savannas. Intact oak savannas are among the rarest ecosystems in the world.

open wetland: a wetland that is an open system where there exists an exchange of water, sediment, nutrients, pollution, organisms, and energy with surrounding area. An open wetland is affected by land use in the surround watershed.

marsh: a wetland that is permanently flooded or is frequently flooded by adjacent streams, rivers, ponds, or lakes during periods of high water. Marshes are characterized by submersed, floating-leaved vegetation or emergent soft-stemmed vegetation adapted to saturated soil conditions. There are many different kinds of marshes, but all types receive most of their water from surface water, and many marshes are also fed by groundwater. There is an abundance of plant and animal life because nutrients are plentiful and the pH is neutral. Learn more at

pioneer species: a hardy species that is first to colonize disturbed or degraded habitats, initially dominating the community. As conditions improve, it allows other plants to move in, leading to a more stable and biodiverse ecosystem.

prairie: an ecosystem native to central North America characterized by forbs and tall grasses with few, if any, trees.

prescribed fire: the planned use of fire to regenerate growth, control invasive species, and improve wildlife habitat.

remnant prairie: a small remaining portion of an original prairie.

ridge and swale: a type of topography closely associated with Great Lakes shorelines where the land roughly takes the shape of flowing waves that form parallel to the lakeshore. Consisting of sand, the rising hump of the wave is the ridge and the hump that drops is the swale. The low swales are often wet and filled with water, while the ridges remain dry. This mix of wet and dry creates two distinct communities of plants that live side-by-side.

scat: 1) the excrement of an animal; poop. 2) a style of singing where the singer substitutes improvised nonsense syllables for the words of a song, which could very likely include sounds like “doo-doo” and “poo-poo.”

sedge: a grasslike plant with triangular stems and a spiked inflorescence of inconspicuous flowers.

sedge meadow (aka wet meadow and dry marsh): A closed wetland community with saturated soil often composed of peat and muck, home to perennial plants including sedges, grasses, and occasional forbs. Frequently acting as a transition zone between aquatic communities and uplands, they often hold no standing water, but they are deeply mucky underfoot.

seep: in a fen, the wide area of porous soil where water escapes, or seeps, to the surface.

sesquipedalian: 1) measuring a foot and a half. 2) pertaining to a long, polysyllabic word that happens to describe itself.

tallgrass prairie: The same as “prairie” (above). The descriptor “tallgrass” is a misnomer because the majority of plants in a tallgrass prairie are flowers (forbs).

wetland: a place on the landscape where water dominates or greatly influences the biological chemistry of the area. Examples include lakes, ponds, marshes, sedge meadows, wet prairies, fens, bogs, swamps, and flooded areas around rivers and streams. Learn more at

woodland: a plant community with 50 to 80 percent tree canopy cover—denser than a savanna and more open than a forest.