Florida and sea-level rise

Florida is one of the US states most vulnerable to sea-level rise because of the low elevation of its land surface. The major cities along the coast, as well as Everglades National Park, are at greatest risk.

Background

Located in the southeastern corner of the United States, Florida is the nation’s fourth most populous state. The state’s land surface consists largely of a peninsula extending southward, bordered by the Gulf of Mexico on the west, Florida Bay on the south, and the Atlantic Ocean on the east. A panhandle that trends west from the peninsula is bordered by Georgia and Alabama on the north. The highest point in Florida is only 105 meters above sea level; the rest of the state is low-lying, with a fairly level surface.

Flooding

Flooding is a potential hazard for all of Florida’s coastal areas, because the land is so flat and the ground surface is only a few meters above sea level. Heavy downpours cause serious problems. Storm drains and canals are designed to carry off excess water by gravity flow, but most of them empty into the ocean or lagoons behind the barrier islands, so a future sea-level rise would reduce the effectiveness of these drains and canals, aggravating flooding problems.

Beach Erosion

Florida beaches experience severe erosion during storms and hurricanes, and this erosion will continue and increase if sea levels rise. Erosion along undeveloped sections of the coast is already cutting beaches back by as much as 0.5 meter per year. In developed areas, preventing beach erosion is a costly process. Property owners must armor their beachfront property with protective sea walls, or groins, while cities have to undertake dredge-and-fill projects, known as “beach renourishment” projects. Not only do the latter cost millions of dollars per kilometer, but also sand dredged from offshore is often the same fine-grained sand that was washed away in the first place. Once it is replaced on the beaches, it is as easily washed away again, so the life expectancy of renourished beaches is just a few years or even less.

Florida’s population is concentrated in the coastal zone, where the amount of residential and commercial development has steadily increased. Owners have torn down their oceanfront cottages to replace them with two-story mini-mansions, and, where single-family houses once stood, multi-story condominiums have risen. The vegetated sand dunes that once protected the coastline from beach erosion have been largely replaced by concrete structures, but many of these have proven to be just as vulnerable to wave attack as the dunes were, and some have even had to be torn down.

Hurricane Damage

Hurricanes are intense storms that form over warm ocean waters. Because of its southerly location, Florida may experience several of these each year. With continued warming of the oceans, Florida’s hurricanes will probably occur more frequently and with greater intensity. The hurricane season lasts from June 1 until November 30, with two periods of peak activity. The first such period comes in June, when smaller storms form in the Caribbean Sea and the Gulf of Mexico, because the waters there warm first. The second activity peak comes in September, when the normally cool waters off the coast of Africa start to warm up and severe Category 5 storms may develop. The damage caused by hurricanes results from high winds as well as from the accompanying storm surges. The lower, southeastern coast of Florida has been most affected by hurricane damage over the years, but no part of Florida has gone untouched. Powerful hurricanes, including Hurricane Irma (2017), Hurricane Ian (2022), and Hurricane Milton (2024), continued to strike Florida throughout the 2010s and 2020s.

Infrastructure Damage

Rising sea levels will affect Florida’s highways, bridges, houses, factories, waterways, ports, airports, mass transit systems, sewage treatment plants, and water supply facilities. Unfortunately, many of these systems are already under stress as a result of long-term deferral of maintenance. In addition, the productivity of the coastal lands for agriculture, residences, tourism, recreation, and industry will be affected by rising sea levels, as will Florida’s estuaries, wetlands, and coastal groundwater tables. Worse still, as salt water from the ocean intrudes along the coast, the well fields from which many Florida cities get their drinking water will become contaminated.

Environmental Changes

South Florida is classified as subtropical because of its mild winter season. Central and North Florida have more severe winters, with frequent freezing temperatures. However, global warming could cause South Florida to become tropical and cause Central Florida to develop the subtropical characteristics South Florida now has. These temperature changes would result in longer growing seasons and a poleward shift of certain plant and animal ranges. Mangroves would grow farther north, for example, and cypress, which are not tolerant of salt water, would decline and eventually die, as the rising ocean waters extended inland. Humans would be affected as well: Heat-related deaths could increase, and tropical diseases could spread. South Florida already has occasional cases of St. Louis encephalitis and malaria. The numbers of these cases would probably increase as temperatures warmed, and dengue fever could appear as well.

Context

Florida is low-lying and has one of the longest coastlines of any US state. As a result, it would be severely affected should sea levels rise as a result of global warming. Geologists believe that, prior to the last ice age, worldwide sea levels stood some 95-125 meters higher than present levels. As the highest point in Florida is only 105 meters above sea level, the entire state must have been submerged at that time. Evidence for this can be found in the old sandbars and seashells scattered everywhere on the Florida land surface. A rise in sea level of only 15 meters would submerge all of South Florida, including the Everglades. If all the ice on the planet melts, the entire state of Florida will disappear beneath the waves.

During the 2020s, studies showed that global climate change was causing sea levels to rise at an increasing rate. Some estimates show that sea levels could be as much as two feet higher than their 2024 levels by the year 2060. This would have catastrophic consequences for Florida and other coastal regions, placing many areas underwater.

Key Concepts

• Category 5 storm: the most severe hurricane possible, with winds of at least 250 kilometers per hour and a storm surge of at least 5.5 meters
• Everglades: a vast sawgrass marsh with occasional wooded “tree islands”
• groundwater table: the upper surface of the underground zone saturated with water
• St. Louis encephalitis: a form of sleeping sickness
• storm surge: an abnormally large sea-level rise occurring during a severe storm
• subtropics: a climate zone found just poleward of the tropics
• tropics: a climate zone found close to the equator that lacks a winter season

Bibliography

Braasch, Gary. Earth Under Fire: How Global Warming Is Changing the World. Berkeley: University of California Press, 2007.

Bush, D., et al. Living with Florida’s Atlantic Beaches: Coastal Hazards from Amelia Island to Key West. Hong Kong: Duke University Press, 2004.

Green, Amy. "In the South, Sea Level Rise Accelerates at Some of the Most Extreme Rates on Earth." Inside Climate News, 11 July 2024, insideclimatenews.org/news/11072024/florida-sea-level-rise-accelerates-at-extreme-rates/. Accessed 21 Dec. 2024.

Warrick, R. A., E. M. Barrow, and T. M. L. Wigley, eds. Climate and Sea Level Change: Observations, Implications, and Projections. New York: Cambridge University Press, 1993.