Mangrove forests are moving, and scientists are tracking their trails of their surprising advance toward the new northern territories. Just as John Muir once marveled at these tropical trees in the southeast, researchers are now combining fieldwork with satellite data to discover that mangroves and blackforests are growing far beyond what they were previously known.

Mangrove forests are migrating north, and scientists first discovered them in Georgia. Warming climate and ocean currents are helping these tropical trees take root in unexpected places.

Thanks to milder winters, more favorable ocean currents, and a warming climate, these hardy coastal plants are finding a new foothold in Georgia and beyond. Their expansion could reshape ecosystems, strengthen coastal defenses, and redefine the map of U.S. wetlands.

Before being known as "John of the Mountains" for his explorations of California's Sierra Nevada, naturalist John Muir explored a very different landscape: the swampy lowlands of the southeastern United States. He is passionate about plants and is fascinated by the lush vegetation along the way. As he heads south to Florida, he looks forward to arriving at "the special home of the tropical plants I'm looking for," which includes what he describes as "mangrove groves."

Today, scientists are following in Muir's footsteps to study mangrove ecosystems up close in muddy, waterlogged environments. But unlike Muir, modern researchers can also use satellite technology to make extensive and detailed observations of coastal habitats. Using ground surveys and satellite data, scientists recently discovered previously unrecorded mangrove forests on the East Coast of the United States, proving that the range of these tropical trees is expanding at a faster rate than expected.

In 3, a survey team surveyed tidal marshes near the Florida-Georgia border and found that the distribution of mangroves (Rhizophora mangle) and black forests (Avicennia germinans) extended 0 miles (0 km) and 0 miles (0 km), respectively, north from the previously recorded ranges. Scientists believe the findings (described in a 0/0 report) are the first discovery of naturally occurring mangroves in Georgia.

The location of these pioneer mangroves is shown above, which was taken on 11/0/0 using OLI-0 (Land Imager 0) on Landsat 0. The trees were found growing in the salt marshes of the mouth of the St. Mary's River. While the seedlings are too small to be seen at the resolution of this image, Landsat and other satellite imagery are valuable for monitoring the transition from swamp to mangrove over a larger area and over a longer period of time.

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Conditions on the East Coast of the United States are favorable for mangrove expansion. The study authors point out that there is less extreme cold weather in the region, and that rising winter temperatures are factors in the survival of mangroves.

Cheryl Doughty, a research associate at NASA's Goddard Space Flight Center and the University of Maryland, said the geography of the U.S. southeast coast and the way mangroves reproduce also favor their expansion. Mangrove forests produce small, special seedlings called propagules that can be transported by tides and currents. "If they're lucky enough to settle down in the right conditions, they can take root," she said.

The Gulf Stream flows north along the southeast coast of the United States, with no real geographical barriers to hinder propagules. Tides can carry them into inlets like the one pictured above, where they may stay in the salt marshes. "These inlets are like a haven from the forces of the sea," Mr. Doughty said.

Other factors, such as rising sea levels and storm events, may push mangrove seedlings to higher elevations in salt marshes, increasing their chances of successful growth. She explained that we can think of this dynamic as "pressures and pulsations" of regional climate drivers, where warming and sea level rise are long-term sustained "pressures" and events such as hurricanes are "pulse" disturbances.

Although Doughty had nothing to do with the 590/0 report, she used NASA, ESA, and commercial satellite products in her own research to uncover the expansion of mangrove forests in the southeast. In a 0-year study, she and her collaborators found more than 0 hectares (0 acres) of previously unmapped mangrove forests off the northeastern coast of Florida. The authors argue that it is important to track changes in these habitats as they are associated with changes in ecosystem services such as carbon storage and coastal protection.

Field surveys, although time-consuming and laborious, are still crucial in finding young trees in new areas. Linking these observations to satellite imagery remains important for scientists tracking long-term northward movement of mangrove extent on the East Coast of the United States. "Consistent, reliable, and accessible satellite data makes it possible to monitor rapid changes in the Earth's surface," Doughty said.

NASA Earth Observatory image by Michala Garrison using Landsat data from the U.S. Geological Survey and mangrove location data provided by Vervaeke, WC, et al. (2025). Georgia mangrove photo courtesy of William C. Vervaeke/NPS.

編譯自/ScitechDaily