Purchased Environmentally Endangered Lands

Southeast Florida is home to one of the crown jewels of biological diversity in the state.

• Read more about pine rocklands

The tropical hardwood hammock is an ecosystem consisting of broad-leafed trees, shrubs, and vines, nearly all of which are native to the West Indies, with Live Oak (Quercus virginiana) being the only significant temperate species. Subject to thin soils and a tropical climate, hardwood hammocks form a dense canopy with a tangle of shrubs and vines at the ground level and its outer edges.

Historically, tropical hammocks were found as far north as Cape Canaveral on the Atlantic coast and to the mouth of the Manatee River in Tampa Bay on the Gulf coast. Now, most of the hammocks have been lost to development, leaving small patches of hammock habitat in South Florida.

Hammocks occur in marshes, pinelands, mangrove swamps, and the interiors of some wetland tree islands. Hammocks develop at elevations high enough to prevent seasonal flooding. The dense shade created by a mature hammock regulates the temperature inside, keeping them several degrees cooler during the summer months, and sheltering the hammock interior from winter winds.

Although fire is a necessary characteristic of other forest communities in South Florida, the hardwood hammock is intolerant of fire. The sparse understory, dense shade of the canopy, and permeating moisture of a hammock helps to insulate them from fire. In very dry periods however, hammocks become more vulnerable to wildfire, and a major burn can completely destroy a hammock.

Since hammocks typically have a dense canopy, few understory plants grow, but a thick barrier of shrubs and vines usually dominates the fringe of a hammock, making entry difficult. The wildlife that inhabits a hammock is derived almost entirely from southeastern temperate North America and the West Indies. The most common sightings are of birds, the Florida tree snail, lizards, an occasional owl, and raccoons. The lush, rich vegetation is the focal point of this forest.

Commonly found trees and shrubs

• Florida Royal Palm (Roystonea elata)
• Live Oak (Quercus virginiana)
• Pigeon Plum (Coccoloba diversifolia)
• Wild Tamarind (Lysiloma latisiliqua)
• Gumbo Limbo (Bursera simaruba)
• Strangler Fig (Ficus aurea)
• Paradise Tree (Simarouba glauca)
• Poisonwood (Metopium toxiferum)

Wetlands contribute to water quality by removing excess nutrients and pollutants that originated in the uplands before they reach the estuary. 

• Read about freshwater and coastal wetlands

Thought to be the oldest habitat in Florida, scrub habitat formed 10,000 to 100,000 years ago when sea levels were higher. As the seas rose and retreated, sandy island ridges formed from coastal dunes, creating patches of isolated land. Over thousands of years, plants and animals adapted to the dry sandy ridges and evolved in isolation.

Because the plants and animals adapted to the unique conditions of these ridges, over half the species found in scrub are endemic to this habitat, meaning they are found no where else in the world. Most scrub is found in Central Florida, although the habitat does extend south into northern Miami-Dade County.

Scrub is a critically endangered habitat, threatened by citrus farms, cattle grazing, urban development and invasion of exotic species.

Wildlife

A scrub landscape has open sandy areas scattered with tall pines, short oak and palmetto trees, and small herbaceous plants. Like the habitat, many plants and animals found in scrub are threatened or endangered.

Endangered gopher tortoises burrow dens up to 30 feet long in the open white sand, emerging to eat saw palmetto berries and the endangered paw paw’s yellow fruit. Burrowing owls and other animals also use the tortoise holes for shelter. Small threatened scrub lizards sun on rosemary bushes, waiting for insects and spiders.

The blue gray Florida scrub jay, a threatened species found only in Florida, flutters from scrub palmetto to cabbage palm looking for spiders, young frogs and snakes to eat.

Scrub in Miami-Dade County

In Miami-Dade County, scrub is found at the southern end of its range, in the form of scrubby flatwoods. Two transitional areas of scrubby flatwoods still exist in northern Miami-Dade County: "County Line Scrub" and the "Dolphin Center Addition."

Both sites have been acquired for conservation by Miami-Dade County's Environmentally Endangered Lands (EEL) Program. These two isolated sites represent the last remaining remnants in Miami-Dade County of this old and formerly extensive ecosystem.

For more information on Scrub Ecosystems, visit the Archbold Biological Station.