Featured Article Summary #149

Before drainage, the Everglades in southern Florida were a vast network of marshes and prairies covering about 4,000 square miles. It is both a large watershed stretching from Lake Okeechobee to Florida Bay and a collection of many connected ecosystems within the same region, so it can be called either “the Everglades” or “Everglades.” Marjory Stoneman Douglas described it as a “River of Grass,” showing how water and plants blend together. While sawgrass and sloughs are well-known, other habitats like pinelands, tropical hardwood hammocks, cypress areas, and mangrove zones are also important for wildlife. The freshwater flowing toward Florida Bay mixes with saltwater, which helps mangroves and coastal marine life thrive, including seagrasses that benefit from steady freshwater discharge. These habitats constantly change because drainage patterns, geology, climate, storms, and fire affect water flow and conditions, making the system both fragile and resilient. The Everglades is relatively young, only about 5,000 years old in geological terms. Its ecosystems constantly change because of the water’s type and amount, the region’s geology, and how often and how severely fires occur. Water is the main force shaping the Everglades, influencing how the limestone was worn away and how fresh water moved to create springs, sinkholes, and a vast wetland ecosystem. The region has two seasons—wet and dry—and rainfall varies, with droughts, floods, and tropical storms common; during heavy wet-season periods, water slowly flows from Lake Okeechobee to Florida Bay and supports freshwater marshes dominated by sawgrass. Tropical cyclones and hurricanes repeatedly change the coastline and plant life by sweeping out vegetation, spreading seeds and plants, and sometimes killing mangroves, though many areas regrow and may even gain new nesting habitat after storms. The Everglades formed because of southern Florida’s underlying geology. Limestone made from compressed calcium carbonate (including porous remains of tiny marine life) stores water, and how long areas stay flooded (the hydroperiod) controls the type of soils and plants that grow. Short floods support periphyton and marl, while longer flooding allows peat to build up over thousands of years, later breaking down when oxygen returns and causes rapid decay and subsidence. Farming and development near Lake Okeechobee often failed because drying turned nutrient-poor peat into less useful material, leading to major soil loss over time—especially in the Everglades Agricultural Area. Fire helps maintain the Everglades. Most fires are started by lightning in the wet season and usually burn only the surface, which helps plant growth and keeps larger shrubs and trees from taking over, while also changing how water moves across the marsh. In the dry season, fires can burn deeper into peat and destroy roots, and over long time periods fires follow cycles linked to wet and dry conditions, with very severe events indicated by charcoal layers in ancient peat.