Florida mangroves can reduce flooding and insurance costs, new study shows

Researchers say mangroves reduce flooding, damages

A Florida mangrove forest. (Image: The Nature Conservancy)

Scientists have known for years mangroves can help prevent flood damage along Florida coastal areas, but the researchers behind a new study hope insurance companies will include mangroves when assessing risks and in turn save counties money.

The study, led by the Nature Conservancy Florida chapter, analyzed mangroves and if they can be used to measure benefits for insurance companies that assess coastal properties and coastal infrastructure.

Mangroves, along with other coastal ecosystems such as salt marshes, beaches and coral reefs offer protection from coastal storms, flooding and surges, said Laura Geselbracht, the senior marine scientist at the Nature Conservancy's Florida chapter.

According to the Nature Conservancy's website, mangrove forests have numerous benefits including improving water quality, capturing carbon dioxide and greenhouse gases, and providing a habitat for wildlife.

The Nature Conservancy partnered with researchers from the University of California Santa Cruz and Risk Management Solutions, a risk modeling company, which has an industry-standard model to assess risks and damages following storms.

"RMS graciously let us use the model, they did the model runs for us to, to allow us to look at what an Irma like storm, what the damages would be with the mangroves intact and with the mangroves gone, and when you take the difference between that, you can see what the value of those mangroves were in the case of Irma," said Geselbracht, who was on contributing researches on the study.

Geselbracht said these findings indicate mangroves in Collier, Lee and Miami-Dade County saved $1.5 billion in damages during Irma-like storms.

"It is in the Nature Conservancy's interest to be able to quantify, to show what that value is and that it can be assessed and quantified, and by partnering with an insurance company that has the industry-standard model that allows us to do that," Geselbracht said.

On left: Mangrove effects on total population flooded during Hurricane Irma. On right: Changes in Hurricane Irma flood damages to properties due to mangroves. (Image: The Nature Conservancy)

She hopes the insurance industry will embrace these findings in the future when assessing risks and property insurance costs along coastal communities.

"This work helps to identify where to invest cost effectively in habitat restoration and conservation, which is critical for building coastal resilience," said Michael Beck, UC Santa Cruz professor and project team leader, in a news release.

Protecting coastal cities is becoming more important because growing population, climate change and new developments increase the risk of flooding and storm surges.

"This study underlines the critical role-played by natural defenses in the reduction of economic losses from hurricane-driven storm surges and the importance of properly accounting for mangroves and other coastal habitats in coastal flood risk models," said Christopher Thomas, lead modeler at Risk Management Solutions.​​​​​​

Geselbracht said mangroves, along with other coastal ecosystems such as salt marshes, beaches and coral reefs, offer protection from coastal storms, flooding and surges. According to the Nature Conservancy's website, mangrove forests improve water quality, capture carbon dioxide and greenhouse gases, and provide a habitat for wildlife.

"It's in the interest of the Nature Conservancy to make sure this message gets out, about how important these systems are for our protection especially as climate change progresses, and our tropical storms get stronger, and they get wetter and they get slower, it's really important to have these systems in place," Geselbracht said.

Despite their environmental benefits, mangroves are threatened because of coastal development.

"They're protected and yet, you know, people do remove them and people do over-trim them and also when seawalls go in that cuts off our coastal ecosystems from that connection with our coastal waters which is so important for wildlife and fisheries habitats," Geselbracht said.

General schematic of mangrove effects on surge level. Surge is reduced behind mangroves reducing flooding to land and properties. Mangroves block surge thus water levels (Image credit: The Nature Conservancy)

Although Geselbracht acknowledges people have a natural inclination to build concrete seawalls along the shoreline and these structures have a place, she said coastal ecosystems are more cost-effective in the long run. 

"They can essentially heal themselves; they can have, you know, a lot less maintenance over the long term," she said. "So, there's a lot of reasons to protect our coastal ecosystems."

Geselbracht emphasized the main thing people can do to protect mangrove forests is recognize the huge asset they are and continue to invest in protecting and restoring them.

"If you can demonstrate it and quantify the benefits," Geselbracht said, "maybe this will take off like wildfires, I hope, and more people will implement these types of strategies along our coastal areas."