Five types of peat appear in the Everglades system; each type supports a specific type of vegetation, such as sawgrass, tree islands, or custard apple trees.[17] Peat buildup is possible because water prevents oxygen from quickly decomposing plant matter. Once peat buildup reaches the surface, oxygen reacts with the microorganisms to decay the peat rapidly in a process called subsidence. Initial attempts at developing agriculture near Lake Okeechobee were successful, but the nutrients in the peat quickly deteriorated by drying, and were broken down by bacteria in the soil. The dried peat burned or was degraded into carbon dioxide and water by microorganisms. Some homes built near early farms had to restructure their foundations on stilts as the peat deteriorated; other areas lost approximately 8 feet (2.4 m) of soil depth.[18] Between the 1880s and 2005, an estimated 3.4 billion metric tons of soil has been lost in the Everglades due to oxidation. Most of that loss occurs in the Everglades Agricultural Area; the least amount of loss is found in Everglades National Park.[19]