Nature-based solutions implications for the eastern Amazon Coastline: The role of mangrove in coastal protection

Abstract

The coastal region serves as a crucial link between the ocean and the mainland, with its morphology significantly shaped by seasonal meteorological and oceanographic conditions. This study was conducted in Salinópolis, located in the state of Pará in northern Brazil, along the eastern sector of the Amazon coast. This area is characterized by a coastal system influenced by semi-diurnal macro tides and waves, alongside notable seasonality in rainfall patterns. Data collection occurred during 2022 and 2023, encompassing both dry and rainy seasons and including neap and spring tides. Observations were made at two sites: a mangrove forest (P1) and a reconstructed retaining wall (P2) designed to mitigate erosion. The data collected included current speed and direction, turbidity, and salinity. Results revealed a 70–80 % reduction in current velocity at the mangrove site (P1) compared to the retaining wall site (P2), underscoring the mangrove forest’s effectiveness in dampening wave and tidal energy. Salinity varied significantly between the dry (∼30 PSU) and rainy (∼8 PSU) seasons, showing a 70 % reduction. Additionally, suspended sediment concentration was higher during the rainy season (∼114 mg/L), representing an 80 % increase compared to the dry season (∼29 mg/L), attributed to higher sediment input from local rivers. This study represents the first evaluation of mangrove forests as nature-based solutions for coastal protection in the Amazon region. It highlights the potential of such ecosystems not only for coastal preservation but also for the conservation of the region’s threatened biodiversity, which is increasingly at risk due to coastal urban development.