Global mangrove forests have begun to recover after decades of decline, with satellite data showing a net increase of nearly 2,000 square kilometres since 2010, driven by expansion in Asia, Australia and South America, according to a study published in Science.
Scientists analysing Landsat imagery collected between 1984 and 2023 found that mangrove forests lost nearly 3,000 square kilometres (1,200 square miles) between 1984 and 2010, followed by an increase of nearly 2,000 square kilometres (770 square miles) after 2010. The researchers also observed that many remaining mangrove forests now have denser, more closed canopies than they did in 2010, a sign of healthier, less degraded forests, particularly in South America.
“Other research groups have mapped and analyzed long-term changes in select regions, but these are the first global mangrove maps that cover such a long period,” said Zhen Zhang, an environmental scientist at Tulane University. “About two-thirds of the expansion was due to mangroves colonizing new areas and the other third due to restoration and regrowth in degraded areas,” he added.
One of the most notable turnarounds occurred in Southeast Asia, especially Burma (Myanmar). The country lost mangroves rapidly in the 1980s and 1990s due to agriculture, aquaculture, and firewood harvesting, but the trend reversed around 2010. The authors attribute the shift to increased awareness and restoration efforts after the 2004 Indian Ocean tsunami, strengthened legal protections for forests, and high rates of sedimentation that created new mudflats.
Landsat images of Palaw Township in Burma’s Myeik District show mangrove expansion in the area, where much of the regeneration appears to be occurring in abandoned rice fields. People on nearby Pyin Bukyi Island have experimented with conservation and tree-planting projects. Despite the gains, Burma lost 28.6 per cent of its mangrove area between the 1980s and 2010; since then, its mangrove area has grown about 10 per cent.
Elsewhere, extensive sediment deposition around the mouth of the Amazon River and in northern Australia has created new mudflats that mangroves have colonised, contributing to steady increases in both regions since the 1990s. At the northern and southern edges of their range, including the southeastern United States, warming temperatures and fewer freezes have allowed mangroves to expand into areas that were previously too cold, Zhang explained.
In some areas, 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 experienced widespread degradation after tropical cyclones damaged broad swaths of mangroves.
“The global successes we’ve seen with mangroves during the past decade should not be seen as grounds for complacency,” cautioned Zhang. “This underscores that conservation and slowing deforestation can lead to huge positive impacts when coupled with natural expansion and regeneration.”
The study was published in Science.
Analysis
Why This Matters
- Mangrove forests store up to four times as much carbon per area as taller inland tropical forests, making their recovery a significant development for climate mitigation.
- The trees protect coastal communities from erosion and storm surges, and their root systems provide habitat for fish, shrimp, crabs and other marine life.
- The research demonstrates that conservation and restoration can reverse deforestation trends at a global scale when combined with natural processes.
Background
The first Landsat satellite launched in the 1970s, and for decades satellite data showed a story of mangrove loss and decline. The new study provides the first global mangrove maps covering a period of nearly 40 years, from 1984 to 2023, and reveals a reversal beginning around 2010.
Key Perspectives
Zhen Zhang (Tulane University environmental scientist): About two-thirds of the expansion came from mangroves colonising new areas and the other third from restoration and regrowth in degraded areas. He also noted that warming temperatures have allowed mangroves to push into areas that were previously too cold at the northern and southern edges of their range.
Zhang (cautionary note): The global successes should not be seen as grounds for complacency; conservation and slowing deforestation lead to huge positive impacts when coupled with natural expansion and regeneration.
What to Watch
- Whether the expansion trend continues in Asia, Australia and South America as restoration efforts and sediment deposition persist.
- The fate of mangroves in West and Central Africa, where losses in the Niger Delta have continued since 2010.
- How future tropical cyclones and warming temperatures affect mangrove health and range, particularly in North America and southern Africa.
Checked
12 claims in this story checked against 1 source: 11 supported.
Show each claim
- SupportedGlobal mangrove forests have staged an unexpected rebound, shown by satellite data.NASA: “A global rebound began around 2010, the scientists found, led by the expansion of mangrove forests in Asia, Australia, and South America.”
- SupportedMangroves gained nearly 2,000 square kilometres since 2010, reversing decades of decline.NASA: “For decades, the story they told about mangroves was dominated by loss and decline. Research published in Science suggests that the tide has turned.”
- SupportedResearchers analysed Landsat imagery from 1984 to 2023 and found nearly 3,000 square kilometres lost through 2010, followed by nearly 2,000 square kilometres gained after 2010.NASA: “The researchers analyzed Landsat imagery collected between 1984 and 2023... They 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.”
- SupportedZhen Zhang said these were the first global mangrove maps covering such a long period.NASA: ““Other research groups have mapped and analyzed long-term changes in select regions, but these are the first global mangrove maps that cover such a long period,” said Zhen Zhang, an environmental scientist at Tulane University.”
- SupportedZhang said about two-thirds of the expansion came from mangroves colonizing new areas and the other third from restoration and regrowth in degraded areas.NASA: ““About two-thirds of the expansion was due to mangroves colonizing new areas and the other third due to restoration and regrowth in degraded areas,” he added.”
- Partly supportedBurma lost mangroves rapidly in the 1980s and 1990s because of agriculture, aquaculture and firewood harvesting.NASA: “The country lost mangroves rapidly in the 1980s and 1990s due to the expansion of agriculture, aquaculture, and firewood harvesting in coastal areas”
- SupportedThe authors attributed Burma’s turnaround to increased awareness and restoration after the 2004 tsunami, stronger forest protections and high sedimentation that opened new mudflats.NASA: “The authors attribute the turnaround to increased awareness and restoration efforts after the devastating Indian Ocean tsunami in 2004 , strengthened legal protections for forests, and high rates of sedimentation that opened up new mudflats for colonization.”
- SupportedBurma lost 28.6 per cent of its mangrove area between the 1980s and 2010, then its area grew about 10 per cent.NASA: “which lost 28.6 percent of its mangrove area between the 1980s and 2010. Since then, the country’s mangrove area has grown about 10 percent.”
- SupportedSediment deposition around the Amazon mouth and in northern Australia created mudflats that mangroves colonised, contributing to steady regional increases since the 1990s.NASA: “extensive deposition of sediment has created new mudflats that mangroves have successfully colonized, contributing to steady increases in each of these regions since the 1990s.”
- SupportedWarming temperatures and fewer freezes have allowed mangroves to expand into previously too-cold areas at the edges of their range, including the southeastern United States.NASA: “At the northern and southern edges of their range, including the southeastern U.S., warming temperatures and fewer freezes have also allowed mangroves to push into areas that were previously too cold, Zhang explained.”
- SupportedZhang cautioned that global mangrove successes during the past decade should not lead to complacency.NASA: ““The global successes we’ve seen with mangroves during the past decade should not be seen as grounds for complacency,” cautioned Zhang.”
- SupportedZhang said conservation and slowing deforestation can have large positive impacts when combined with natural expansion and regeneration.NASA: ““This underscores that conservation and slowing deforestation can lead to huge positive impacts when coupled with natural expansion and regeneration.””
