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New Study: One of a Kind Freshwater Mangrove Forests Discovered in the Amazon Delta

Findings by National Geographic Explorers highlight how previously unknown freshwater mangrove forests exhibit a different structure compared to other mangroves around the world

District of Bailique, Brazil - 2022/04/15: A network intertwining mangrove roots. Credit: Corey Robinson/National Geographic

Photograph by District of Bailique, Brazil - 2022/04/15: A network intertwining mangrove roots. Credit: Corey Robinson/National Geographic

Washington, D.C. (July 20, 2022) — Data from a new paper published today in Current Biology has identified a new phenomenon in the Brazilian coast: freshwater mangroves.

These unique freshwater mangroves were found along the Amazon Delta and provide proof of ecosystem adaptability to the Amazon river flow. This study is the first scientific finding published as part of the National Geographic and Rolex Perpetual Planet Amazon Expedition, a two-year exploration of the Amazon River Basin from the Andes to the Atlantic.

From April 10 to April 27, 2022 National Geographic Explorers Angelo Bernardino and Thiago Silva conducted the first exploration of 11 mangrove forests along the Amazon delta. The Explorers analyzed data from the soil pore water, salinity, composition, tree density and volume using 3-D laser scanning from the ground and from drones.

The study shows that the Amazon river plume and high rainfall conditions allow the coexistence of a unique set of mangroves. These mangrove structures, which yield little to no salinity, have never been documented on deltas or coastal fringing mangroves anywhere in the world.

Bernardino and Silva also found that the sampled mangrove forests exhibited a one-of-a-kind structure in comparison to other mangroves that have been studied worldwide. Globally, very few mangroves have been found to thrive in such low-saline environments, and only one other site has reported estuarine mangroves growing in freshwater conditions.

As a result of their unique structure, these mangrove forests will likely provide distinct ecosystem functioning, carbon stocks, and support for related animal and plant species over their large expanse. The lower salinity may influence soil functions including pollutant retention, carbon sequestration, and greenhouse gas emissions. Additionally, the distinct soil properties of this coastal region further set the stage for the diverse plant species found in this atypical mangrove setting, which has not yet been observed in any other region of the world.

“It was phenomenal to see this type of freshwater flooded forests in this environment,” said Bernardino. “This discovery is critical to further understanding the intricacies of mangrove forests and how they are crucial to local communities that surround them.”

Findings from Bernardino and Silva’s research also signify the expansion of the existing mapped mangroves of the Amazon delta by nearly 20% with an additional 180 square kilometers. This research reveals the importance of field explorations on the Earth’s natural habitats, as existing satellite imagery had not detected mangroves in a significant area of the Amazon Delta.

“Ecologically, mangroves provide a habitat for a diverse array of organisms. They are a natural laboratory for how we understand plants,” said Silva. “The findings from the 3-D terrestrial laser scanning allows us to see from aerial root density to tree height and volume, develop new methods to estimate carbon stocks, follow where the individual trees are, and even see underground channels of vegetation. It’s fascinating.”

The second phase of this research is currently underway in Pará, Brazil, where Bernardino and National Geographic Explorer Margaret Owuor will survey and document the economic and social value mangrove forests provide to Amazonian communities.

“The expedition into the Brazilian mangrove forest and subsequent discovery of freshwater mangroves is critical to painting the full picture of the vast Amazon River Basin,” said Nicole Alexiev, Vice President of Science and Innovation at National Geographic Society. “Through the multi-year expedition of the Amazon supported by Rolex’s Perpetual Planet initiative, we will continue to gather new information about these critical ecosystems and how we can support solutions to ensure their protection.

To learn more about Perpetual Planet Expeditions visit:


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The National Geographic and Rolex partnership supports expeditions to explore the planet’s most critical environments. By harnessing world-renowned scientific expertise and cutting-edge technology that reveal new insights about the systems that are vital to life on Earth, these expeditions help scientists, decision-makers, and local communities plan for and find solutions to the impacts of climate and environmental change while illuminating the wonder of our world through impactful storytelling.


For nearly a century, Rolex has supported pioneering explorers pushing back the boundaries of human endeavour. The company has moved from championing exploration for the sake of discovery to protecting the planet, committing for the long term to support individuals and organizations using science to understand and devise solutions to today’s environmental challenges.

This engagement was reinforced with the launch of the Perpetual Planet initiative in 2019, which initially focused on individuals who contribute to a better world through the Rolex Awards for Enterprise, on safeguarding the oceans through a partnership with Mission Blue, and on understanding climate change as part of its association with the National Geographic Society.

An expanding portfolio of other partnerships embraced by the Perpetual Planet initiative now include: the Under The Pole expeditions, pushing the boundaries of underwater exploration; the One Ocean Foundation and Menkab, both protecting cetacean biodiversity in the Mediterranean; the Xunaan-Ha Expedition, shedding light on water quality in Yucatán, Mexico; the B.I.G expedition to the North Pole in 2023, gathering data on threats to the Arctic; Hearts In The Ice, also collecting climate change information in the Arctic; the Monaco Blue Initiative that brings together experts on solutions for ocean conservation.

Rolex also supports organizations and initiatives fostering the next generations of explorers, scientists and conservationists through scholarships and grants such as Our World-Underwater Scholarship Society and The Rolex Explorers Club Grants.

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About National Geographic Society

The National Geographic Society is a global nonprofit organization that uses the power of science, exploration, education and storytelling to illuminate and protect the wonder of our world. Since 1888, National Geographic has pushed the boundaries of exploration, investing in bold people and transformative ideas, providing more than 15,000 grants for work across all seven continents, reaching 3 million students each year through education offerings, and engaging audiences around the globe through signature experiences, stories and content. To learn more, visit or follow us on Instagram, LinkedIn, and Facebook.