Unless you have a private boat or seaplane, the only way to get to Dry Tortugas National Park, the southernmost terminus of the United States, is on a ferry called the Yankee Freedom III that docks in Key West, Florida. The park encompasses seven islands 70 miles from both Key West and Cuba. The islands, called keys, are small, low-lying and formed on the beds of ancient coral reefs. These keys anchor the park like a constellation, yet they make up less than one percent of the 46 square miles of parkland. The rest is ocean.

Garden Key, the second largest island, is home to Fort Jefferson, the fortress that attracts tens of thousands of visitors per year. I became one such tourist on a cool morning in mid-March. The day I took the ferry, I woke up at my campsite on inland Key West, about six miles from the harbor, at 5am. I put on my bathing suit and covered it with leggings and a jacket. I stretched my headlamp over my bicycle helmet, and I cycled to the harbor through a sleeping island, past roosters and cuban coffee stands. By the time the ferry left, the wind was snapping the flag off the end of the boat and the waves across the strait were five to seven feet high.

Before Fort Jefferson, Dry Tortugas was a graveyard of treasure. In 1513, Spanish explorer Ponce de Leon became the first European to set food on the islands and gave them their namesake — Tortugas is Spanish for turtle, after the sea turtles his crew feasted upon, and “Dry” referencing the disappointing lack of freshwater on the islands. For centuries afterward, ships used the channel to cross from the Caribbean into the Gulf of Mexico and crashed into the keys, drowning literal chests of treasure.

When we docked two hours later, the waters surrounding Garden Key were turquoise blue, clear and flat like a swimming pool. Pelicans stood on old wooden posts that jutted out of the bay and sailboats dropped anchor a few hundred feet out. Sooty terns, a bird species that nest on Bush Key when the water is low, swooped across a land bridge connecting the two islands like tufts of grey cotton. Numbering around 80,000, it’s the only colony of sooty terns in North America. Bush Key is only two feet above sea level. The highest elevation within Dry Tortugas, Loggerhead Key, which hosts the single lighthouse in the Keys, is only ten feet above sea level.

I zipped up my jacket to hold out the breeze and walked across the moat and through the high arch of Fort Jefferson. Small stickers from the large infield of the fort hitched to the bottom of my sandals. I leaned into a cannon storage unit to pull them out. The cannon cache dates Fort Jefferson to the 19th century, and specifically, the War of 1812. During the war, Washington, D.C. burned to the ground and America’s coastal navy was decimated by Britain’s deep water ships. The U.S., humiliated, created a system of fortification from Maine all the way down to Texas. Their most impressive fort was to be built at the entrance to the Gulf of Mexico: Dry Tortugas was the perfect spot.

The U.S. spent 30 years building a colossal octagon so foreboding that no one would attack it. Fort Jefferson is a titan of American empire. It’s the largest all-masonry fort in the U.S. with over 16 million bricks stacked into 2,000 archways, supporting 175 cannons, and 110 cisterns to store fresh water. In its 16 acres of land, it stored enough supplies to support a small army for a year long siege. In the days of its creation, slaves, nearly 20 percent of the workforce, mined local coral around Bush Key to make concrete. The concrete was used to shape spiral staircases, parapets, ramparts, and a four foot wide sea wall.

Fort Jefferson was never finished. Engineers worried the island couldn’t support the additional weight of both cannon and brick. It was abandoned in 1874 and instead used as a station for ships to refuel on coal. In 1935, under President Roosevelt Dry Tortugas became a national monument. Over half a century later, in 1992, it became a national park. But just as the American government reneged on its plans for Fort Jefferson, it’s also reneging on its commitment to our national parklands. The unwillingness to work to reverse the effects of global climate change means it’s failing to protect the fragile islands that this fortification was built upon.

The keys of Dry Tortugas could be underwater, along with Everglades National Park and much of the southern peninsula of Florida, within 80 years. Current projections show that in the next two to three centuries, sea levels will rise 12 feet, possibly submerging the entire state. Global warming is the main culprit, increasing water levels through melting snow and ice and expanding the mass of oceanic water that already exists. Warming oceans take up more space and cause more erratic weather patterns including an increase in the frequency and intensity of hurricanes.

The keys have always been shape shifters. They grow and they shrink from hurricanes and wave breaks, but the current climate threatens to overtake them and their fragile ecosystems. Before the century’s out, it is possible that what was once one of America’s most ambitious defense fortress will be partially underwater, and the southernmost National Park in America will be the first of our public lands to actually disappear.

Before I left I swam in those rising waters off a beach near the sea wall that boasts coral, turtles, and bright, tropical fish for snorkelers. The water was muddled from all the wind offshore and I couldn’t see anything through my goggles but I knew somewhere out there was a whole world worth protecting.

[divider]Guest Contributor[/divider]

Austyn Gaffney is a freelance writer and editor based in Kentucky. Her work is published or forthcoming in Brevity, The Offing, Prairie Schooner, and RANGE, and it has been attributed in The Rumpus. Her reporting has been featured by the Natural Resources Defense Council and Scalawag Magazine. You can follow her adventures on www.southeast-ern.com and on Instagram at @austyneg.