Satellite images show mangrove forests are now expanding after decades of decline
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After decades of declining human development and extreme weather, the world’s mangroves are growing again, according to a startling new study that looks at satellite images of coastal forests.
Zhen Zhang, lead author and postdoctoral researcher at Tulane University in New Orleans, says the study points to early signs that restoration and conservation efforts are working.
In addition to human efforts, Zhang said mangrove forests have shown resilience and resilience on their own.
Mangroves provide significant benefits to local communities. They are important habitats for fish and marine life, supporting important fisheries that feed millions. They protect coastal areas from floods and storms, which are becoming increasingly important in the face of rising sea levels and extreme weather caused by climate change.
They also store more carbon than other forests, making them important in the fight against global warming.
Using satellite images from NASA’s Landsat program, researchers were able to create a detailed picture of the global mangrove canopy over time.
Mangroves have been declining since the 1980s, the study found, but since 2010 there has been more growth than decline.
The data showed that two-thirds of the mangrove expansion occurred in new coastal areas, while the rest was regrowth in former forest areas.
The surprising finding does not mean that mangroves everywhere are healthy. Research shows that forests are facing loss in West and Central Africa.
Zhang said mangroves are sensitive to extreme weather conditions, which can destroy years of progress. As examples, he pointed to winter snow in Texas five years ago and rising sea levels causing landslides in 2022-23 in French Guiana.
It means that although mangroves regenerate naturally, those benefits still need to be protected.
“The future fate of mangroves depends entirely on whether we can continue to reduce the rate of deforestation,” Zhang said.
Mangroves are always under threat
But it’s not all good news, as research has been shared in the mangrove research area.
Heather Stewart is a biologist with the US Fish and Wildlife Service who works in Florida’s mangrove wildlife refuges. He says that while it’s encouraging to see mangroves growing, that doesn’t make up for the decline in the first place.
“They’re still missing that initial point where the research started. So it’s not back to those 1980 levels,” said Stewart, who was not involved with the Tulane study. “There is still a long way to go.”
New mangrove areas are also not the same as old, mature forests, Stewart said. As the study suggests, the new areas are likely to be made up of young trees that do not provide the same levels of carbon storage and other ecosystem benefits that older forests provide.
“When you lose a mature forest, a hectare or a hectare of that mature forest is not equal to the same area of these young, young mangroves,” he said.
The overall benefit of mangroves is “a positive trend,” Stewart said, but individual forests bring different benefits to local areas — supporting different types of marine life, filtering water or protecting against flooding.
Even if the overall mangrove cover increases, those local benefits can be lost if the mangroves move to new areas.
“We must focus more on stopping deforestation and the degradation of these mature forests,” he said. “Because the mature mangrove forests are the ones that will be able to resist diseases, they help people a lot.”
