Planting trees along coastlines with man-made coastal defenses, such as dikes, could protect more than 140,000 people from flooding and save up to $800 million from flood damage globally each year, a new study shows.
Places that have mangroves, such as parts of Florida, are better able to withstand the ravages of storms and their powerful waves. But while there is a push to restore mangroves around the world, there are several challenges.
But places in Florida with mangroves so 30% less damage than areas without mangroves, saving around $13 billion. “Mangroves act as a sponge for incoming waves,” Daniel Friessan environmental scientist at Tulane University, told LiveScience. “Their dense tangle of above-ground roots are good at soaking up incoming wave energy.”
Mangroves are forests which is found in the intertidal zone between sea and land. Their trees can live in the salty water and they are found in tropical and subtropical coastal zones.
Climate change is expected make hurricanes more frequentand rising sea levels will drive higher storm surges. Mangroves protect local communities and infrastructure from these waves.
They can also help combat climate change. ONE 2025 study found that restoring 1.1 million hectares (2.7 million acres) of mangroves globally would remove about 0.93 gigatons of carbon dioxide from the atmosphere. It is almost triple emissions from cars in the USA. It would cost about $10.73 billion to restore these mangroves, according to the study.
Despite their importance, the world’s mangroves are at risk. More than half of the earth’s mangrove ecosystems are at risk of collapse by 2050according to an assessment from 2024 of International Union for Conservation of Nature. They are replaced by agriculture and aquaculture.
Balancing costs and benefits
Researchers wanted to see how mangrove restoration around the world could protect people and prevent costly damage from flooding, as well as determine where these measures could have the greatest impact.
In the study, published January 20 in the journal PNASthey modeled the effects of mangroves when the forests were combined with flood defences, such as dikes or seawalls. Dikes are man-made structures which run along the sea or rivers to prevent water from flowing onto land.
“We used a published mangrove restoration tool, which looks at where the mangroves have been lost based on satellite data, the hydrological conditions in those areas now” to determine whether these mangroves can be restored, says lead author of the study Timothy Begging Acta climate adaptation specialist at the Vrije Universiteit Amsterdam, told LiveScience. The team then combined this information with flood risk, future climate scenarios, changes in GDP and population, and sea level rise.
They found that mangrove dike systems could save a total of $800 million globally and protect 140,000 people from flooding each year. These figures increased during different climate scenarios linked to human carbon emissions.
Their cost-benefit analysis suggests that in a high-emissions scenario, where Earth’s climate changes dramatically, every dollar spent on mangrove dike systems globally could ultimately generate – or save – $6. It could be worth as much as $125 billion by 2100.
However, the benefits were not the same everywhere. Countries in Southeast Asia would see the biggest benefits – about $270 million a year and 70,000 people sheltered from flooding. West Africa was a close second, saving about $221 million and protecting 38,000 people. Nationally, Nigeria, India and Indonesia would benefit most from restoring mangroves in front of man-made coastal defences.
In the US, Florida would see significant benefits from restoring its mangroves, but Louisiana would reap even greater returns, the study found.
Jonas Buschan environmental economist and a former senior researcher at the Center for Global Development who was not involved in the research welcomed the study. “It combines the biophysical analysis of mangrove restoration with the engineering of levees, and then economics,” he said.
However, he would like to see a breakdown of the economic benefits of mangroves alone. “They assume places already have dikes and then you can add mangroves on top of that,” he said.
The authors flagged this as a limitation of the study. The analysis depends on a flood protection database, which shows existing infrastructureand can’t tell if the dikes are strong enough or even still standing.
Gray-green strategies
Adaptation strategies that combine nature-based solutions and engineered infrastructure are sometimes called for grey-green infrastructure. This area is “a new, open and important topic,” Busch said.
Other examples include combining forest management with home hardening (which involves retrofitting or building houses with flame retardant materials) to reduce fire risk, and combining dam maintenance with upstream watershed restoration.
“There is no doubt that a hybrid approach can be a pragmatic and effective approach” to coastal management, Thomas Westhoffa nature-based solution manager at the non-profit organization for conservation Wetlands Internationaltold LiveScience.com. That was especially the case along heavily urbanized, receding coastlines that have lost much of their mangrove cover, he added.
Westoff cautioned that there is no one-size-fits-all solution. “Whether this is a feasible solution is very context-specific,” he said, adding that dikes may not exist in many areas.
But “in many regions, healthy mangrove belts can still provide enough of a buffer for coasts and communities as the climate changes,” Westhoff said.
Challenges in restoring mangroves
There is a global push to restore mangroves, but a majority of these projects — up to 80% — fail.
“Restoring mangroves is a good idea, but these projects are difficult to implement,” Tiggeloven said. Sometimes mangroves are planted in unsuitable places or the wrong type of trees are planted.
Successful projects require community buy-in, Westhoff said. “When communities benefit directly from restored ecosystems—either through sustainable harvesting or ecotourism—they are more likely to protect them for the future.”
Additionally, when restoring or preserving a mangrove, people may want to develop the land in other, more profitable ways, Busch noted.
“Mangroves have to compete with that from an economic perspective,” he said. The new paper “is a key part of that, because it shows the economic value of mangroves’ storm protection.”
