Before urban development of the South Florida region, pine rocklands covered around 161,660 acres (654.2 km2) in Miami-Dade County. Pine forests were extensively cleared by urban developers and the lumber industry in the 1930s and 1940s.[50] Within Everglades National Park, 19,840 acres (80.3 km2) of pine rockland communities are protected, but outside the park, 1,780 acres (7.2 km2) of pine forests remain as of 1990, averaging 12.1 acres (0.049 km2) in size.[50] Dade County pine has a remarkable longevity and has proven to be termite-resistant, though dense enough to make driving nails difficult.[54] In 1984 they were protected by a county ordinance, after many pine areas had been depleted. A misunderstanding of fire's role also played a part in the disappearance of pine forests, as natural fires were put out and pine rocklands transitioned into hardwood hammocks.[50] Today prescribed fires occur in Everglades National Park in pine rocklands every three to seven years.