Story of an Elusive Paradise: The Deep History of Southwest Florida

The following was originally written for my class at Green Mountain College, Bioregional Theory and the Foodshed in December 2014.

“The place of understanding is not necessarily kind. Heaven and earth meet there, and they will crush you if you do not hold them apart… Nature is fire and ice and gravity, falling rocks and rushing streams, but it moves well through myth and poetry: voices, sounding through the smoke.” – C.L. Rawlins

The deep history of southwest Florida comes, like its opalescent beaches, in waves. Only the capricious ocean currents and epochal sea level fluctuations could create conditions unique enough to form crushed coral underbellies, quartz sand shorelines, and cavernous wonderlands. Here, the tides play the architect. Over the millennia, waters come and go, followed by sea creatures and land dwellers, migrating and layering and leaving their bodies in humble fossils, a cryptic note from the past to all who call this place home of its sirenic and inconstant character.

As part of its mystical past, Florida was, curiously, once a part of northern Africa, at a time when two ancient supercontinents collided to form the well known grandmother landmass, Pangea. Geologists have gained more evidence for this theory by measuring magnetic characteristics in rock from Florida and matching it to that of northern Africa – they have found more harmony there than in rocks present in surrounding North America (Lane 1994, 11-14). Years passed; continents drifted apart. Sometime between the Miocene epoch, twenty-three through five million years ago, and Pleistocene, about 1.8 million through ten thousand years ago (Lane 1994, 22), Florida had reached relative tectonic stability (Scholl and Stuiver 1967, 444). Once the continents were in their near-contemporary places, other changes, as a matter of course in our dynamic world, continued. Several features contribute to the basins and elevations shaping the region we see today. Rising down the spine of the peninsula is the Lake Wales Ridge, summiting with Sugarloaf Mountain at 308 feet above sea level (USGS 2014). The Ocala Platform, a limestone formation, hugs the region to the north, and the Peace River Formation traverses the center of southwest Florida (Tihansky and Knochenmus 2013). The Peace River Formation begins at the southern end of the Ocala Platform stretching south to the Okeechobee Basin. Interbedded sands, clays, and carbonates constitute the Peace River Formation, which is rich in phosphorus (2013).

Next to leave its mark on this canvas was temperature via its reign over water levels. Several ice ages came and went throughout the Pleistocene epoch. Due to planetary temperature’s command on glacial activity, sea levels surrounding lowland shoreline varied dramatically throughout these times. Across the peninsula, sea levels varied from one hundred fifty feet above today’s level, to four hundred feet below contemporary shorelines (see figure 1).

During the times when high sea levels swallowed up earth, the Florida shelf was an ideal shallow temperate zone for tropical corals to grow and develop extensive reefs. As the waters slowly crept in on lands, at their highest, reaching just more than three hundred feet above sea level, peninsular Florida became an ephemeral coral reef (see figure 2, submerged Florida platform). As the waters retreated during the times when the ice was frozen, coral reefs on higher lands, now exposed, died off, compacted, and became limestone. This repetitious cycle formed the layers of the soft limestone bedrock of Florida (Lane 1994). The lower water table also contributed to the formation of one of Florida’s most interesting geological features: caves and freshwater aquifers. As rain collected carbon dioxide in the air and filtered into the ground, it created a mild carbonic acid, which over centuries dissolved the soft limestone forming caverns. Streams caused erosion over time (termed “sinking streams”) and eventually connected with the caverns to open them up and form the surface springs we see today (Gulley et al. 2013, 1211). Currents and waves allowed phosphorus to collect in Central Florida; it would become a lucrative but environmentally dangerous industry in contemporary times (Lane 1994, 19; Froelich et al. 1985). Another architect of the soft limestone, phosphorus-loving plankton, settled here. Through their lifecycles they deposited organic matter over Florida’s surface, especially contributing to the mucky soil of the Everglades region. Incoming waters via the Gulf Trough (see figure 2, emergent Florida platform) deposited siliciclastic sediments, or quartz sand, on top of the limestone bedrock, which eventually resulted in award-winning fine-grained white sand beaches (Lane 1994, 18; Scholl and Stuiver 1967, 440).

During the times when Florida rose up over the low sea levels, in the late Pleistocene, the region was much like a dry savanna, open prairie and scrub grasslands covered southern Florida and much of the global freshwater was trapped north in Canadian glaciers (Hoppe et al. 1999, 441). Dry tolerant flora such as oaks, grasses, and Asteraceae (ragweed) dominated the landscape (Lane 1994, 23). The Pleistocene was also the time of the megafauna: mammoths, mastodons, giant sloths, dire wolves, saber-toothed tigers, and others roamed the earth (Lane 1994, 26). The fossilized remains of these and other megafauna can be found in central and north Florida springs, rivers, and sinkholes. Their remains date back before the last major ice age, about twenty to forty million years ago, which was likely the cause of their demise (Larson 1995, 31). Scientists speculate that as the climate changed, mammoth, who require extensive territories, lost habitat and fewer food resources were available, contributing to their extinction (Hoppe et al. 1999, 442).

Not to be overshadowed by mastodon bones, intriguing tiny invertebrate fossils are prolific in southwest and all over Florida. It was this constant influx and retreat of waters over Florida which trapped many of them. E.H. Sellards wrote, in his 1919 account of his explorations in Florida, that “nowhere in the United States do the Tertiary and Quarternary [sic] formations contain a more abundant, more varied, or better preserved marine invertebrate fauna than in Florida. In the study of the fossils, Florida is in many respects a state of exceptional opportunities” (286). Not only have ancient marine fossils been an ongoing treasure hunt to Florida’s past, but the earliest Florida human remains were found at Little Salt Springs in Sarasota County. The specimen dates from at least 10,000 years ago, around when humans first arrived on the Florida peninsula. Some scientists speculate that these may be the oldest human remains in North America east of the Mississippi River (Clausen, Brooks, and Wesolowsky 1975, 204). After the last ice age, as the earth warmed and sea levels continued to rise, freshwater became more prolific, and Florida evolved into the tropical climate and plant life we see today.

The plentiful water and tropical climate helped support the Tocobaga Native Americans among other tribes, who inhabited the bioregion near the Tampa Bay area. They utilized the floral resources, such as the palm thatch for roofing material as well as hunting and foraging local edible plants (Ricky 1998, 242, 258). Another influential tribe of the Everglades is the Miccosukee, who were forced south from the Carolinas by white expansion in the 1800s. The Miccosukee foraged Florida native plants, and they also used palmetto leaves for thatched roofs and created dugout canoes from cypress timbers (Ricky 1998, 178-179). Early Everglades inhabitants hunted, fished, created marine shell tools, used fire; they may have been the first in North America to make fiber-tempered pottery (Schwadron 2006).

The swamps and flatlands which supported humankind’s evolution in this region are the two natural ecosystems found most abundantly in southwest Florida. In the lowlands, true Florida swamps evolved about five thousand years ago, and cypress trees, which characterize Florida swamps, have existed here since about twenty thousand years ago (Larson 1995, 31). The Peace River Basin contributes to many of the southwest Florida cypress swamps, fed by a kaleidoscope of streams, rivers, and lakes. This watershed covers 2,300 square miles, and the Peace River runs through the center of the basin, beginning in the Green Swamp Lake Region and emptying into Charlotte Harbor (Our Phosphate Risk 2008). Ferns, another living fossil, (see figure 3) are a common inhabitant of Florida swamps; more species of fern grow in Florida than any other state in the continental United States (Larson 1995, 75). In addition to cypress domes, which are typically swampy year-round, ephemeral, or seasonal, wet areas abound. In ephemeral swamps, hardwood tree stands, bayheads (boggy areas with mucky soil) (Florida Department of Environmental Protection 2011), and grassy marshes grow (Beever and Thomas 2006, 1). Ephemeral ponds are a critical home to wildlife in Florida, especially wading birds like herons and egrets. Wetlands are also home to today’s manatee, American alligator, little blue heron, Audubon’s crested caracara, roseate spoonbill, snowy egret, river otter, and many others (Beever and Thomas 2006, 7, 24).

As elevation rises inland, the pine flatwoods take over. Various types of pine trees, like slash and longleaf, and saw palmetto dominate the landscape. The understory of this ecosystem, saw palmetto, produces a berry which is a food staple for the Florida black bear and other wildlife (Beever and Thomas 2006, 8). The pine flatwoods are also home to the endangered Florida panther, fox squirrel, bald eagle, gopher tortoise, Florida long-tailed weasel, bobcat, white-tailed deer, red-cockaded woodpecker, and eastern indigo snake among many others (Beever and Thomas 2006, 10-12). Though drier than the swamps, the flatwoods do experience an intense wet season. It entails dramatic tropical thunderstorms that whip the tall thin pines and flood the landscape with rainwater. The characteristic lightning storms makes this area the lightning capital of North America at ninety-one thunder days per year, occasionally inciting forest fires (Christian et al. 2003). The flatwoods ecosystem is highly adapted and dependent on regular fire for its lifecycle functions (Beever and Thomas 2006, 8). Every two to four years, the fires rage through the landscape, preventing shrubs and hardwood sprouts from growing, ensuring ground flora biodiversity as the forest floor recovers from the flames (Martin and Kirkman 2009).

White pioneers began farming in Sarasota County in the nineteenth century. They grew sugarcane, sweet potatoes, corn, collard and turnip greens and farmed mostly for subsistence. As they settled in, citrus, corn, and cattle became major crops. To prepare the land, pioneers cleared and burned out the pine and palmetto stumps of the flatlands. Next they used a horse or an ox to pull the plow and till the soil and remove roots, but they found that in the sandy soil the nutrients to feed their annual crops did not last long (Esthus 2003, 3, 25).

In contemporary times, these unique ecosystems have continued to be put at risk due to human actions. The root cause of the disappearance of the natural environment is development. By 1970, only half of the historic flatwoods still remained, and far less exist today. People have over-harvested the saw palmetto berry for medicinal use, which is a part of the Florida black bear’s food supply (Beever and Thomas 2006, 8). Fecal coliform bacteria from agriculture, neighborhood septic system overflow, and spreading of biosolids on the landscape often contaminate this precious ecosystem. The phosphorus laid down millennia ago by ancient waves has been mined for agricultural use in chemical fertilizers, which has caused “catastrophic” phosphate pollution in the Peace River (Froelich et al. 1985). Scientists predict that unless strict measures are made to protect the flatwoods, they will soon be totally decimated for use by humans alone: cities, suburbs, and food production (Beever and Thomas 2006, 9-10).

As was the case in times past, Florida continues to face sea level fluctuation today, and as our planet warms, the seas are rising due to the melting of polar ice caps and warmer waters’ molecular expansion. Experts predict that Florida’s coastline will rise twenty to forty inches by the year 2100 (Lausche 2013). As we know, sea level changes are part of what made Florida everything it is today. This time, however, communities are much less mobile than in years past. Hotels and homes are built on barrier islands which naturally move like desert sand dunes. Accelerated global warming is putting Florida, once again, at the mercy of the ocean tides. Sarasota, a coastline community, dependent on the tourism and hospitality of its barrier island resorts, has begun to consider what the effects of sea level rise may be on the population, economy, and way of life. Mote Marine Aquarium and Laboratory, a prestigious local research center, released a report earlier this year recognizing the threat of sea level rise to the seventy-eight percent of Florida’s population who live coastal communities. Their report recommends early planning, building community support, and broadening local planning as we continue to witness southwest Florida’s changing surface (Lausche 2013).

As the shallow mild submerged Florida shelf lured corals to grow on it millennia ago, it has now drawn humankind to build concrete reefs on its balmy shorelines. Will they too someday be bedrock? Will we someday become fossilized memories of a time long past? As we have learned from those before us, this is but a fleeting climate, an elusive paradise.

References:

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