The Oak Openings Region is a globally rare ecosystem composed of over 130 square miles (336.7 km²) in Northwest Ohio. The land consists largely of oak savanna

Oak savanna

An oak savanna is a type of savanna, or lightly forested grassland, where oaks are the dominant tree species. These savannas were maintained historically through wildfires set by lightning, grazing, low precipitation, poor soil, and/or fires set by Native Americans...

 and grassland prairie. It is considered by The Nature Conservancy

The Nature Conservancy

The Nature Conservancy is a US charitable environmental organization that works to preserve the plants, animals, and natural communities that represent the diversity of life on Earth by protecting the lands and waters they need to survive....

 as having a similar ecological importance as the Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

 Everglades

Everglades

The Everglades are subtropical wetlands in the southern portion of the U.S. state of Florida, comprising the southern half of a large watershed. The system begins near Orlando with the Kissimmee River, which discharges into the vast but shallow Lake Okeechobee...

 and is one of the 200 "Last Great Places on Earth".

This unique area was formed after the last age when the continental glacier

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

 melted leaving behind a large lake called Lake Warren. Over time, this lake was gradually reduced to present day Lake Erie

Lake Erie

Lake Erie is the fourth largest lake of the five Great Lakes in North America, and the tenth largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also has the shortest average water residence time. It is bounded on the north by the...

 and left behind a large tract of sandy soil to the west. The area was frequented by wildfire

Wildfire

A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...

s of which only thick-barked oak

Oak

An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...

 trees could survive. When pioneers arrived after first crossing through the Great Black Swamp

Great Black Swamp

The Great Black Swamp, or simply Black Swamp, was a glacially caused wetland in northwest Ohio, United States, extending into extreme northeastern Indiana, that existed from the end of the Wisconsin glaciation until the late 19th century...

 they called the area the "Oak Openings" as a comparison to the thick swamp.

Today, the Oak Openings Preserve Metropark

Oak Openings Preserve Metropark

Oak Openings Preserve Metropark is the largest of the Toledo Area Metroparks. It is a nature preserve located near Swanton, Ohio and is part of the Toledo Metroparks. It is located southwest of the Toledo Express Airport, and contains sand dunes and several rare plant species...

is the largest intact piece of savanna remaining.