The state is best known for its manatees and alligators, but one of the world's most important sea turtle refuges is quietly located just 90 minutes from the theme parks of Orlando.

From a lookout point over the dunes of Melbourne Beach, Florida, I gazed out into the Atlantic Ocean and immediately saw a pair of green sea turtles in the water near the shore. Another popped into view; then another. I counted five pairs within a couple of minutes. On the beach, a small group of people were sunbathing. I wondered if they had any clue that they were likely standing atop hundreds of sea turtle nests at that very moment.

They may not have even known that they were in the Archie Carr National Wildlife Refuge, one of the most important sea turtle nesting sites on the planet, according to David Godfrey, executive director of the Sea Turtle Conservancy. Florida is renowned for unique aquatic adventures like swimming with manatees and sighting dolphins, but each year, thousands of loggerhead and green turtles, as well as dozens of leatherback turtles, make their way across the world's oceans to mate and nest here. Yet the refuge – covering 33km between two unnamed barrier islands, stretching between the towns of Melbourne Beach and Wabasso Beach – is no remote space; it's a coastal destination filled with rows of pastel-coloured beach houses just 90 minutes from the tourist-thronged theme parks of Orlando. Parts were already privately owned when the refuge was established in 1991, so the zone is now a mix of protected wilderness and developed land. Conservation succeeds here not by separating humans and nature, but by allowing for their harmonious coexistence.

Intrigued by this interaction, I'd come to Melbourne Beach to join a sea turtle nesting tour. Because turtles usually nest and hatch at night, our tour began around 21:00 in an auditorium, where we learned about the species while trained scouts cautiously spotted for turtles on the beach. We waited eagerly but patiently, knowing that we wouldn't head to the shore until a turtle had come out of the water, dug a nesting hole and stood over it. Once ready to start laying eggs, the turtle would enter a trance-like state in which we could safely observe her without scaring or disturbing her.

"They don't want to be seen [for fear of predators]", said Nichole Perna, land management specialist at Archie Carr's visitor centre, explaining that bright lights can "deter [them] from nesting". Driven by ancient instinct, female sea turtles typically nest every two or three years on the same beach where they hatched, or in proximity to it. However, they may not be able to nest if a beach has become too bright or noisy, or if barriers – human-made structures like breakwaters and groynes built to counteract coastal erosion – keep them from reaching the sand. Blair Witherington, a research scientist at Inwater Research Group, explained that if this happens, the turtles "will shed their eggs in the water. These won't survive."

As for eggs that are successfully laid: only one in 1,000 make it into adulthood. Many threats cause hatchling mortality; "chief among [them] are light pollution and coastal armouring," said Witherington. Lights can disorient........

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