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The KeysProductive coral reefs, seagrass beds, and mangroves make the Florida Keys one of North America's unique natural ecosystems and a top destination for scuba diving, snorkeling, and sport fishing.
Sea level has fluctuated many times since the formation of the ancient coral reef that is now the upper and middle Keys. Today, sea level is rising. At Looe Key, a spectacular reef system, land is visible only during some low tides. Back in 1744, when a British ship ran aground, the captain later described to the admiralty an island — Looe Key — that measured 350 meters long and 75 meters wide.
The Florida Keys will be strongly affected by future sea level rise. Some may simply disappear from the map. Much of the land in the Keys is extremely low-lying — between zero to around three feet above current sea level. These areas would be severely flooded if predictions of an 18-20 inch rise in sea level during the next 100 years prove accurate.
The Keys already are experiencing rapid sea level rise. Measurements at Key West indicate that sea level has risen about one foot since 1846, and currently is rising at a rate of approximately 15 inches per 100 years.
Higher areas will be more vulnerable to damage from storm surges than they are today. From 1900 to 1994, 36 percent of all U.S. hurricanes hit Florida.
Coral ReefsThe largest living coral reef in the contiguous United States lies seaward of the Florida Keys. This coral ecosystem is more than 130 miles in length, making it the third largest coral reef tract in the world. Extending south from Miami to the Dry Tortugas, the reefs are home to more than 5,500 marine species. The reefs also act as a natural buffer to protect the Keys against catastrophic storm surges from hurricanes.
"Coral reefs are projected to be among the most sensitive ecosystems to long-term climate change."
- Rafe Pomerance
U.S. Deputy Assistant Secretary of State for the Environment and Development, March 5, 1999 |
Climate change could threaten the reef through warmer ocean temperatures, changes in the salinity of water from Florida Bay, and increases in the water's sediment load from coastal erosion.
Corals worldwide can tolerate temperatures only a few degrees higher than normal high temperatures for their particular region. As a result, global warming could exacerbate a phenomenon known as "coral bleaching." Increases in water temperature of one degree Fahrenheit or more for as little as one month often result in extensive coral bleaching, which occurs when warming waters or other stresses cause the expulsion of algae that normally live with the coral. The algae are important for the health of the reef because they provide corals with much of their food and oxygen. Ultimately, the loss of these algae may kill the coral.
A number of stresses or environmental changes may cause bleaching, including disease, excess shade, increased levels of ultraviolet radiation, sedimentation, pollution, salinity changes, and increased temperatures.
MangrovesRapid sea level rise could harm low-lying mangrove communities, affecting the many important environmental functions they provide. Mangrove communities filter out pollution, stabilize sediments, and hold nutrients — all functions that help to protect the shoreline from coastal erosion. Florida's mangrove forests also provide food, nesting, and nursery areas for many animals — including more than 220 fish species, 24 reptile and amphibian species, 18 mammal species, and 181 bird species.
Mangrove trees have special salt-filtering roots that allow them to obtain freshwater from saltwater. The trees produce peat by trapping sediments in the water, and the process of building peat normally allows mangroves to keep up with rising sea levels. Some researchers believe that mangroves can withstand a sea level rise of only four to five inches per century — considerably less than that projected for the next 100 years. But others believe the picture is more complicated, and that mangroves in some areas may have little trouble keeping up with sea level rise. In general, the response of mangroves to sea level rise depends on the type of mangroves, their environmental setting, the amount of freshwater available to maintain root growth, and the sediment supply.
Mangrove communities in south Florida already are affected by a number of stresses, including invasive Brazilian Pepper plants, hurricanes, agricultural runoff, and human development. Climate change and a rise in sea level pose new stresses to an ecosystem already in danger.
Searching for SolutionsTo address the threat of global warming, south Florida could improve the health and resiliency of its natural ecosystems, prepare for rising sea levels and other changes, and work to limit future sea level rise and global warming by reducing greenhouse gas emissions.
 Many efforts are underway to restore the Everglades and prevent further harm, including the massive program for "replumbing" the Everglades, the Everglades Forever Act, the South Florida Ecosystem Restoration Task Force, the Florida Governor's Commission for a Sustainable South Florida, and other federal, state, and tribal ecological restoration efforts. These programs may help improve the ability of the Everglades and other south Florida ecosystems to adapt to climate change. A healthier Everglades with improved freshwater flow would be less vulnerable to the stresses of a changing climate, and would slow the invasion of saltwater.
A number of initiatives to protect coral reefs also are underway. For example, the U.S. Coral Reef Initiative, launched in 1996, supports efforts to conserve and sustainably manage coral reefs and related ecosystems such as seagrass beds and mangrove forests.
What People Can DoWe all add greenhouse gases to the atmosphere whenever we use energy from fossil fuels. Residential energy use accounted for 19 percent of overall CO2 emissions from the combustion of fossil fuels in 1997, and motor vehicle use accounted for approximately 20 percent. Here are a few actions that people can take to reduce their emissions.
- If you live in south Florida, you can help restore freshwater flow through the Everglades by saving water: avoid excessive watering of your garden or washing of your car, use low-flow toilets and showerheads.
- Use mass transit, carpool with friends, or ride a bike whenever possible.
- When it's time to replace the family vehicle, consider one that gets more miles per gallon than your present vehicle.
- If you have a small boat for fishing and recreation, run it with "human power" when possible.
- When it's time to replace an appliance, look for the Energy Star® label identifying energy-efficient models.
- When buying or building a new house, an Energy Star model gives greater quality and comfort as well as lower monthly costs. For more information, go to the Energy Star Homes web site.
- Buy products that feature reusable, recyclable, or reduced packaging to save the energy required to manufacture new containers and reduce greenhouse gas emissions from landfills.
- Encourage your company to join EPA programs such as Energy Star BuildingsSM and Waste Wi$e recycling programs, and to buy office equipment with the Energy Star label.
- Plant trees, which absorb carbon dioxide from the air.
- Educate others. Let friends and family know about these practical, energy-saving steps they can take to save money while protecting the environment.
- Encourage scientific research and public discussion on global warming and solutions such as energy efficiency and alternative energy.
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Regional and local planning and zoning policies could take into account the implications of future sea level rise. New development could be set back far enough to allow wetlands to move inland naturally as the sea rises. For example, some states prohibit new houses in areas likely to be eroded in the next 30-60 years. Other states have implemented some version of "rolling easements" in which landowners are allowed to build but only on the condition that they will remove the structure if and when it is threatened by an advancing shoreline.
Programs to help endangered species recover and to help restore ecosystems also could factor in future sea level rise. Conservation officials could try to ensure that species have somewhere to move when the sea rises — a challenge in south Florida where so much land already is developed.
Slowing Climate ChangeToday, action is occurring at every level to reduce, avoid, and better understand the risks associated with global warming. Many cities and states across the country have prepared inventories of their greenhouse gas emissions, and a number of them are pursuing programs and policies that will result in reductions of those emissions.
At the national level, the federal government is working in partnership with businesses, states, and local governments to address global warming. In addition, the U.S. Global Change Research Program coordinates the world's most extensive research effort on climate change.
For More Information
- The Florida Coastal Management Program at 850-488-1554, or Florida Sea Grant (Miami-Dade County) at 305-361-4017 can provide background information on south Florida and its coastal environment.
- The U.S. Environmental Protection Agency's Global Warming site includes detailed information on climate change, impacts, and actions.
- The National Park Service's web site
 provides links to south Florida's national parks, preserves, monuments, and seashores.
- The U.S. Fish and Wildlife Service's web site provides information on wildlife refuges in south Florida.
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