NASA Reports Global Mangrove Rebound After Decades of Decline

After decades of decline, mangrove forests are making a global comeback, according to NASA Earth Observatory. Scientists analyzed Landsat imagery collected between 1984 and 2023 and found that a global rebound began around 2010.

Global Expansion and Regional Gains

Researchers tallied losses of nearly 3,000 square kilometers (1,200 square miles) between 1984 and 2010, followed by an unexpected increase of nearly 2,000 square kilometers (770 square miles) of mangroves after 2010. The expansion was led by mangrove forests in Asia, Australia, and South America.

About two-thirds of the expansion was due to mangroves colonizing new areas, and the other third was due to restoration and regrowth in degraded areas, said Zhen Zhang, an environmental scientist at Tulane University.

In Burma (Myanmar), mangrove area began expanding around 2010 after rapid losses in the 1980s and 1990s. The country lost 28.6 percent of its mangrove area between the 1980s and 2010, and since then its mangrove area has grown about 10 percent. The authors attribute the turnaround to increased awareness and restoration efforts after the 2004 Indian Ocean tsunami, strengthened legal protections, and high rates of sedimentation that opened up new mudflats for colonization.

Extensive sediment deposition has also created new mudflats around the mouth of the Amazon River and in northern Australia, contributing to steady increases in each region since the 1990s. At the northern and southern edges of their range, including the southeastern U.S., warming temperatures and fewer freezes have allowed mangroves to push into areas that were previously too cold.

Ongoing Losses and Ecological Role

There are areas where losses have outweighed gains. Substantial mangrove losses in the Niger Delta have reduced the total mangrove area in West and Central Africa since 2010. North America and southern Africa have seen widespread degradation after tropical cyclones devastated broad swaths of mangroves.

Mangrove trees average about 13 meters (43 feet) in height, and mangrove ecosystems store up to four times as much carbon as taller inland tropical forests. The trees protect coastal communities from erosion and storm surges, and their stilt-like roots provide habitat and nursery grounds for fish, shrimp, crabs, and other marine life.

"The global successes we've seen with mangroves during the past decade should not be seen as grounds for complacency," cautioned Zhang.

Why it matters

The rebound shows that conservation, slowing deforestation, natural expansion, and regeneration can produce large positive impacts for coastal ecosystems and carbon storage, though some regions continue to experience significant losses.

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Sources

• science.nasa.gov: A Global Rebound for Mangroves - NASA Science

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