The Everglades is a natural region of tropical wetlands in the southern portion of the U.S. state of Florida, comprising the southern half of a large drainage basin within the Neotropical realm. The ecosystem it forms is not presently found anywhere else on earth. The system begins near Orlando with the Kissimmee River, which discharges into the vast but shallow Lake Okeechobee. Water leaving the lake in the wet season forms a slow-moving river wide and over long, flowing southward across a limestone shelf to Florida Bay at the southern end of the state. The Everglades experience a wide range of weather patterns, from frequent flooding in the wet season to drought in the dry season. Throughout the 20th century, the Everglades suffered significant loss of habitat and environmental degradation.