Most coastal habitats from Cape Canaveral in Brevard County to Miami in Dade County have been highly fragmented due to development. In Brevard County alone, the natural scrub community is estimated to have diminished by 69 percent during from 1943 to 1991; over roughly the same period, population increased by nearly 3,000 percent.
Except for saw palmetto scrub, the term “scrub” refers to well-drained, open pineland with oak or palmetto understory that are well-adapted to dry conditions. Scrub habitats are further divided into subcategories based on vegetation structure, composition, soil type, geography and fire patterns. Scrub subtypes include coastal scrub, oak scrub, sand pine scrub, rosemary scrub, slash pine scrub, and scrubby flatwoods.
Leaf fall in scrub areas is minimal, and ground cover generally sparse due to shading by overstory trees. Open patches of sand are often present in scrub lands, and where they occur, understory trees and woody shrubs benefit from the intense sunlight that reaches the ground.
Florida's scrub and pine flatwoods consist of similar shrub layers, with pine flatwoods differing by having an open canopy of slash pine intermingled with pond pine. Drier areas tend to be dominated by scrub oaks, while less well-drained areas are dominated by saw palmetto. Many Indian River Lagoon sites feature mixed oak-palmetto shrub layers.
While strong winds and flooding influence the character and structure of scrub habitats, fire has been the historic primary force shaping these ecosystems.
Low leaf fall coupled with sparse ground vegetation reduce overall fire risk, but as sand pines mature, their crowns build up large fuel reserves that feed hot, fast-moving fires. These events regenerate the scrub community and prevents its succession to an oak hammock or scrubby flatwoods community. Fire also disperses pine seeds, recycles minerals back into the earth as ash, and diminishes the oak and palmetto understory.
Many herbaceous scrub species are gap specialists, vulnerable to competition and eventual exclusion from scrub areas. These plants benefit from reduced competition in the burn zone following a fire, as seen by a boost in their abundance in an area after a fire than when the same zone is fire-free for a longer period.
Frequent fires are more beneficial to oak scrub and scrubby flatwoods communities; less frequent fires are more beneficial to sand pine scrub and other pine-dominated scrub types.
East central Florida's barrier islands scrub is dominated primarily by saw palmetto and other common shrubs such as nakedwood, tough buckthorn, rapanea, hercules club, bay, sea grapes and snowberry. Shrubby forms of live oak are also common in coastal scrub communities.
Indicator species for other types of scrub communities include sand pine, myrtle oak, scrub live oak, Chapman's oak, coastalplain goldenaster, and narrowleaf silkgrass.
Some of Florida's most threatened and endangered species rely on scrub habitat—and many species are found only in Florida. Among them are the gopher tortoise, the eastern indigo snake, the southeastern beach mouse, and the Florida scrub jay. Many other animals also utilize scrub areas for feeding and for shelter.
The Florida mouse is entirely restricted to the state; its nearest relatives live in southern Mexico. Burrowing gopher tortoises create a diversity of microhabitats upon which numerous other species rely.