Sonia Ferreira's two-story house with a pool and garden on the Brazilian coast was yet another casualty of the advancing waves of the Atlantic Ocean, pushed higher by climate change.

On a recent visit, the 80-year-old retiree glanced around the mound of rubble left from the home she abandoned before it was destroyed in 2022 by the pounding waves in Atafona, north of Rio de Janeiro.

"I've avoided coming back here because we have many memories. It is so sad," she said, showing images of the house she built 45 years ago on her cellphone.

Global warming, combined with the silting of the Paraiba River, has contributed to the erosion of Atafona's coast, and caused the destruction of 500 houses, including the collapse of a four-storey building by the beach.

This is just one of countless beachside communities losing their battles to the ocean up and down Brazil's 8,500 kilometres of Atlantic coastline.

The sea level has risen 13 centimetres in the region around Atafona in the last 30 years and could rise another 16 centimetres by 2050, according to the United Nations report "Surging Seas in a Warming World" released last month.

Ocean racing toward coastal communities

Coastal areas such as Atafona could see the ocean advance inland by as much as 150 metres in the next 28 years, said Eduardo Bulhoes, a marine geographer from Fluminense Federal University.

"The combination of climate change and global warming … with a river that no longer carries sand to the beaches of Atafona, has caused a catastrophe for its residents and there is no hope that this situation will be reversed," he told Reuters.

Although dramatic, Atafona's plight is not unique in Brazil.

The beach in Ponta Negra, one of the most popular seaside resorts on Brazil's northeast shoulder, is also shrinking. In the last two decades, it has lost 15 metres of white sand to the sea. The local government is bringing sand from elsewhere in an expensive effort to recover the beach.

At the mouth of the mighty Amazon River, a fragile ecosystem is threatened with a loss of biodiversity as the river has lost strength in the region's most severe drought on record, letting salt water from the ocean advance upstream.

"Salt water comes further up the river and this will change the whole biodiversity of that area," said oceanographer Ronaldo Christofoletti, at the Federal University of Sao Paulo.

Last year, salt water reached almost as far upriver as Macapa, a city 150 kilometres from the mouth of the Amazon, killing freshwater fish and impacting local fishing communities.

Climate change causing huge rise in sea levels

The Intergovernmental Panel on Climate Change (IPCC), the UN body for assessing the science related to climate change, reported that sea levels are rising faster than ever, with the rate more than doubling in the past 10 years to 0.48 centimetres a year, compared to 0.21 centimetres annually from 1993 to 2002.

Christofoletti said the loss of land in coastal towns and beaches is inevitable with rising seas, questioning why city planning had not adapted.

"It is shocking to see houses being destroyed in Atafona. But you were not supposed to build houses there. You should have woods, a mangrove swamp, a sandbank, ecosystems that would naturally be prepared to hold the sea," he said.