As towering waves smashed onto Costa Rica's Cocles beach, sucking away much of its sand, surf instructor Leo Downer was scared the coastal road, along with his Toyota car, would be washed into the Caribbean by the ferocious February storm.

Low boulders now sit in place to help shelter Cocles, with its reggae bar and cafes serving rice and beans, where tourists cycle past fruit stalls selling lychees and soursop and signs warn of sloths crossing the beach road.

But as rising seas threaten parts of the tropical eastern coast, dubbed "Little Jamaica," many worry that the visitors who generate numerous jobs in the area – known for its palm-fringed beaches and exotic wildlife – could go elsewhere.

"This year was the craziest I've ever seen... we lost everything - there was no sand, there was nothing, the water was hitting right here, all those trees fell down," said Mr. Downer, pointing to the nearby road amid a torrential downpour.

"I saw the water come under my car, whoosh – it didn't take it, but... I've never seen that before. I think everything is changing, it's a little warning," he said, his family sheltering from the rain under their beach shack surrounded by surfboards.

Global warming could cause sea levels around the world to rise between 70 cm and 1.2 meters (28-47 inches) in the next two centuries, ramping up pressure on the roughly half of the world's population who live near the coast, said a German-led team of researchers in a study published in February.

Scientists say parts of Costa Rica's Caribbean coast have lost at least 20 meters (66 ft) of beach in the past 15 years, as creeping sea levels and changing wave patterns cause coastal erosion, often exacerbated by coral reef degradation.

They warn that higher seas and increasingly unpredictable conditions could start to damage infrastructure and take a heavy economic and social toll. In addition to the creeping effects of climate change, extreme events like hurricanes are likely to worsen the impact on many coastal communities, said Borja Reguero, a researcher at the University of California, Santa Cruz.

Trees are being replanted on parts of Costa Rica's coast to halt erosion and protect livelihoods.

But more extreme conditions demand hefty spending on infrastructure such as wave breaks and sea walls to delay mass relocations, some experts say.

"In 100 years, all of the villages in Costa Rica's Caribbean and Pacific coasts will inevitably be flooded," said Omar Lizano Rodriguez, a University of Costa Rica oceanographer.

"There's not the resources or political will to solve the problem. Costa Rica deals with emergencies but not prevention."

Frightened tourists

Tourism is a mainstay on the tropical coast, some 200 km (125 miles) east of San Jose, where many are descended from the Jamaicans who originally came to work on a jungle railway, and English mixes with Spanish and Patois.

In Cahuita, where the coastal national park draws tourists looking for sloths snoozing in the treetops and howler monkeys leaping through the forest, the sea has already consumed slabs of beach and is starting to menace the sleepy town.

On the wooden veranda of Spencer Seaside Lodging where she works, Araceli Huertas explained storm waves are now much higher than in previous years and sometimes crash over the reinforced sea wall in front, soaking the hotel's rooms.

"The tourists are frightened it's a tidal wave or a tsunami or something, as they don't see this very often," said Mr. Huertas, who has lived in the beach town for 15 years. "Now the sea is calm but when the sea looks very high, they want to leave."

Wild conditions are causing trouble for fishermen who cannot go out in rough seas and are landing smaller catches, said Jose Ash, as two men dragged a boat out of reach of the high tide.

"People who live from the ocean can't go anywhere – it's too dangerous," said the fisherman and tour guide, whose own boat was moored offshore.

"What I hear is they're going to build a dock right here for the fishermen, they're going to put some big stones and jacks out there by the big breakers, but that's just like blah, blah, blah for the past 10 years."

Cahuita's national park regularly has to redraw its coastal paths but an elevated wooden walkway built after parts of the access road were washed away now allows it to stay open even when the sea washes ashore, helping keep local guides in work.

As rising waters push back the park's shorelines and reduce its trees, the animals that tempt visitors to the area are also coming under pressure, said park guard Mirna Cortes Obando.

"All the coastline inside the park has been affected - for example, we've lost nearly 50 meters of beach over the last 10 years," said Cortes, on the veranda of the park's headquarters, which was surrounded by water during recent storms.

"We're losing much of the trees here, the almonds, the sea grapes, the coconuts that the animals use for food."

Together with the non-profit Talamanca-Caribbean Biological Corridor Association, the park is now planting more trees along the coast to limit erosion, while a team monitors the coral reef that helps protect parts of the shore.

Branching out

Some of the young trees such as coconut palms have been wiped out by storms, but they should eventually create a barrier to protect against rising waters, said Julio Barquero Elizondo, marine biologist at the association.

Educational programs are also crucial to better prepare for climate change, said Barquero in Hone Creek village, where hundreds of saplings grow in the non-profit's plant nursery.

"We have to have alternatives and not just think about the beach and the sea – the guides should also know about forest tourism and indigenous communities, to have a broader offering so that climate change won't be so damaging," he said.

Back in Cahuita's national park, wildlife guide Richard Hills-Wilson pointed to the tangle of sun-bleached trunks that was once a broad stretch of sand he played on as child.

He is bracing for the next storms, as he marks 33 years of working in the area next month.

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"The beach is going to go," he said. "If there's no beach, then nobody comes."

This story was reported by the Thomson Reuters Foundation.