Soil degradation affects more than a quarter of the coastal zone in northern Rio de Janeiro state, according to a new study by the Federal Fluminense University (UFF), a public university based in Niterói. The survey mapped four decades of land-use change and identified critical areas of erosion, deforestation and rapid urban expansion.
The most severe stretch runs between Búzios, a well-known beach town east of Rio de Janeiro city, and São Francisco de Itabapoana, near the state’s northern border. Researchers found that more than 25% of land in that region is classified as unstable, linked mainly to deforestation associated with cattle ranching and coffee cultivation.
This article is based on single-source reporting from Poder360, which republished material originally produced by Agência Brasil.
What the Study Found
The inventory examined about 22,000 square kilometers (8,494 square miles) of Rio de Janeiro’s coastal zone between 1984 and 2024. Researchers used satellite images, remote sensing and geographic information systems to track how soil conditions changed over time.
Of the 2,460.85 square kilometers (950 square miles) identified as degraded, 1,916 square kilometers (740 square miles) were classified as unstable areas and listed as high priority for environmental recovery. The areas studied included municipalities between Búzios and São Francisco de Itabapoana, as well as Cachoeiras de Macacu, Maricá and cities on the Costa Verde, including Itaguaí, Mangaratiba, Angra dos Reis and Paraty.
The Costa Verde, or “Green Coast,” is a mountainous and heavily forested stretch south of Rio de Janeiro city. It is known internationally for tourism, beaches and historic coastal towns, but the study says development pressure has increased soil instability in parts of the region.
Landslide and Flood Risks
Mohammad Al Abed, a visiting professor at UFF and the author of the study, said degradation on steep slopes raises the risk of landslides and worsens surface runoff during rainfall. When vegetation is removed, intense and prolonged rains can more easily erode exposed soil.
In the area between Maricá and Búzios, the study linked degradation to agricultural expansion and fast urban growth. On the Costa Verde, including Angra dos Reis and Paraty, researchers observed rill erosion near urban areas and soil instability driven by tourism and new roads.
Urbanization on the Costa Verde grew 254% over the 40-year period analyzed, according to the study.
“This puts communities at risk in municipalities such as Angra dos Reis, where more than 60% of the municipality is susceptible to landslides,” Al Abed said, according to Poder360.
Natural Barriers Under Pressure
The study also pointed to risks for roads, pipelines and homes, as well as higher public costs for responding to natural disasters. Those risks matter in Rio de Janeiro because many coastal towns sit between steep hillsides and the Atlantic Ocean.
In Maricá, 5.88% of degraded areas were associated with fires and the replacement of native vegetation by pasture. The study said fires accounted for 26% of tree-cover loss recorded in the municipality between 2001 and 2023.
Mangroves and restingas, coastal sandbank ecosystems that help protect shorelines from storms and rising seas, have also suffered losses. According to the study, the Costa Verde lost 16.3% of its restinga areas and 47.8% of its wetlands during the period analyzed.
The report frames soil recovery as both an environmental and public-safety issue. Without vegetation and stable ground, coastal communities become more exposed to erosion, flooding and landslides when heavy rains hit.