(CNN) — Florida manatees swim and sleep in the sunshine and golden-brown panthers prowl the shady forests at Everglades National Park.
A swampy wilderness of gnarled cypress stands and waving sawgrass just beyond Miami's suburbs, this 1.5 million-acre UNESCO World Heritage Site can seem timeless.
But rising sea levels have spiked the fresh groundwater beneath the Everglades with salt, and plants and wildlife must quickly adapt to new conditions to survive.
That's why the Everglades are among the eight World Heritage Sites in the Americas included in UNESCO's list of "World Heritage in Danger," an exclusive club of 55 destinations, dominated by war-torn countries and terrorist hotspots.
Stretching from the Florida backwoods to an ancient Peruvian city and ghostly Chilean mines, these eight sites are some of the Americas' most extraordinary places. But they're also sites that UNESCO has found are threatened by "serious and specific" perils, whether human or environmental.
This Earth Day, these eight UNESCO sites underscore the importance of preservation efforts in our backyards -- and invite adventurous travelers to explore them before they further deteriorate.
1. Everglades National Park, United States
This sprawling national park is teeming with life, including some plants and animals that are only found in its steaming, brackish swamps.
Exploring the Everglades is all about nature, whether you're spotting manatees on an airboat tour, watching the stars from a mangrove island or hunting for 39 species of native orchids on a guided kayak trip. Visitors may also spot crocodiles and alligators, since South Florida is the only place in the world where they co-exist.
Why it's at risk: Listed as a World Heritage Site since 1979, the Everglades were added to the "World Heritage in Danger" list for a second time in 2010, because the park's low-lying elevation makes the area vulnerable to rising sea levels driven by a warming climate.
2. Belize Barrier Reef Reserve, Belize
Stretching nearly the entire length of Belize's Caribbean coast, this massive reef system is the largest in the Northern Hemisphere, a chain of coral and sand that's visible from the International Space Station.
From water level, a detailed world comes into focus. Hundreds of cayes lie just above the surface, a constellation of mangrove and sand islands with a coral foundation, and the undersea landscape is remarkably varied.
A patchwork of pinnacle reefs, fringing reefs and barrier reefs makes this a compelling destination for snorkeling, and the Great Blue Hole draws scuba divers from around the world.
Why it's at risk: Since the Belize Barrier Reef was inscribed as a World Heritage Site in 1996, a lack of oversight has led to unsustainable fishing, deteriorating water quality and development. It was listed as threatened in 2009.
3. Chan Chan Archeological Zone, Peru
Hundreds of years before the arrival of Spanish conquistadors, the Chimu people ruled the northern coast of Peru.
A civilization that thrived for hundreds of years, they worshipped the rising moon, worked gold and silver into elegant jewelry and built the sprawling metropolis of Chan Chan, which is still the largest mud brick city in the world.
Before Chan Chan fell to an invading army led by the Inca emperor Topa Inca Yupanqui in 1470, it became a society of powerful elites, highly trained craftsmen and farmers.
Modern-day visitors will find the remains of irrigation canals and adobe architecture, crumbling temples and courtyards that offer a glimpse of the city's glory days.
Why it's at risk: Exposure to more than five hundred years of rainwater has begun to melt the city back into mud, and UNESCO scientists believe that erosion will cause even more damage as a changing climate brings greater extremes of weather. Chan Chan was designated as threatened in 1986, the same year it was added to the World Heritage List.
Chan Chan Archaeological Zone: Entrance fees 10 Peruvian soles, roughly USD $3. Taxis to the Chan Chan archeological site may be hired in Trujillo starting at 60 Peruvian soles, or roughly USD $18.
4. Rio Plátano Biosphere Reserve, Honduras
In the thickly forested northeast of Honduras, the Rio Plátano watershed winds from tropical peaks to the Caribbean coast, passing petroglyphs, traditional indigenous communities and lowland savanna on the way toward the sea.
Endangered great green macaws fly through the largest intact rainforest in Central America, where 411 species of bird have been identified. Four kinds of sea turtles swim along the biosphere's marine boundary, and the Mexican spider monkey -- also on the endangered list -- forages for wild fruits in the canopy.
This is a true adventure frontier, and it's best to explore with a guide who can arrange home stays and transport by truck and boat.
Why it's at risk: Many impoverished communities in the biosphere fish and hunt illegally and clear trees for subsistence farming. The Rio Plátano Biosphere was added to the World Heritage list in 1982 and designated "in danger" for a second time in 2011.
5. Potosí, Bolivia
The dry mountains of the Bolivian Andes are shot through with silver, and indigenous people dug ore from the hills for centuries before the arrival of Europeans.
It wasn't until 1545 that Peruvian Diego Huallpa's discovery of extraordinary silver deposits in Potosí ignited a mining boom that transformed an isolated village into a Spanish Imperial City, sending ships loaded with ore across the Atlantic Ocean.
Silver mines still honeycomb the Cerro de Potosí, or Cerro Rico, the mountain that looms above the high altitude city. Walk the streets of Potosí to find superb colonial-era buildings that blend indigenous design with stately Baroque architecture.
Why it's at risk: Potosí's historic buildings, which were designated as a World Heritage Site in 1987, abut modern parts of the city, with no buffer zone to protect the landmarks. Also, ongoing mining has destabilized the surrounding mountains. Potosí was listed as "in danger" in 2014.
Potosí: Shared taxis from the city of Sucre to Potosí are 35 Bolivianos, roughly USD $5. Sucre can also be reached by air from La Paz, with round-trip flights starting at USD $100.
6. Humberstone and Santa Laura Saltpeter Works, Chile
Now that Chile's salt mines are quiet, these are the country's most haunting ghost towns, a sprawl of abandoned homes, shops and factories in northern Chile's bone-dry Pampas desert.
From 1880 until World War II, the residents of company-run towns unearthed massive deposits of saltpeter, a chemical compound used for making bombs and fertilizer.
Visitors can explore the fascinating places where workers lived, worked and worshipped, then see the mine shafts where they dug the "white gold" of the 19th century.
Why it's at risk: Neglected for years, the saltpeter works were added to both the World Heritage and the "in danger" lists in 2005. An earthquake further damaged buildings in 2014.
7. Portobelo-San Lorenzo, Panama
The high stone walls around this Caribbean town were mostly built in the 17th and 18th centuries to protect Spanish gold and plundered treasure -- so it's no wonder that Portobelo tempted pirates and adventurers from around the Caribbean.
Privateer Henry Morgan sacked the settlement in 1668 before moving on to Panama City, but Portobelo's walls had the last word, keeping watch along the coast for centuries after his death. The fortifications were designated a World Heritage Site in 1980.
Although many visitors explore the ruins at Portobelo on a long day trip from Panama City, spending a night is essential to soak up the laid-back vibe of the fishing town. Watch for sails on the horizon as you walk the fortifications and visit the Black Christ figure in the Iglesia de San Felipe before slipping into the ocean to snorkel with sea turtles.
Why it's at risk: With no defined boundaries around the fortifications, unchecked development threatens the 400 year-old structures, which were added to the list of threatened sites in 2012.
8. Coro, Venezuela
Unravel the roots of Coro's fascinating architecture, and you'll find Moorish influences brought by Spanish conquistadors blended with Dutch building styles imported from Aruba and Curaçao.
Colonial history abounds in a city founded in 1527, just 35 years after the 1492 voyage of Christopher Columbus.
And with a strategic location on the northern coast of Venezuela, The fort at Coro's historic port, La Vela de Coro, was the first place seized in Francisco de Miranda's 1806 campaign to liberate South America from Spanish rule.
Why it's at risk: Coro and its port were inscribed on the World Heritage List in 1993, and added to the "in danger" list in 2005. Heavy rains have damaged some of Coro's historic buildings, and a lack of oversight by the troubled Venezuelan government means development threatens the site's integrity.