Florida's Mangroves Aren't Recovering After Hurricane Irma—Here's What It Means for Coastal Communities

In 2017, Hurricane Irma struck Florida and devastated the area. The category 5 hurricane caused serious damage to the region's mangrove forests. Now, a paper published in Nature Communications spotlights the impact on the forests after the hurricane.

The East Carolina University study, in partnership with NASA and Florida International University, brings yet more urgency to the requirement to take care of the natural ecosystems along our coastlines and brings lessons for coastal communities in what not to do. It spotlights the importance of future storm planning and resilience building along our coasts.

Mangrove forests are not as resilient as they were before

It is common for mangroves to suffer damage after a major hurricane. A huge area—as big as 24,000 football fields—died back completely after Hurricane Irma. However, researchers found mangrove forests in Florida has neither rebounded as successfully nor shown as much resilience as it has in the past.

Coastal communities are amongst the most vulnerable globally to the effects of our climate crisis. Rising sea levels, flooding, and more regular extreme weather events all threaten lives and livelihoods along our coasts. Coastal wetlands like mangrove forests have a crucial mitigating effect on coastal threats.

In Florida alone, they prevent more than $11 billion of annual property and flood damage. Of course, these wetlands are also crucial carbon sinks–sequestering carbon and keeping it out of the atmosphere. The impacts of their loss are incalculable but are certainly severe. 

Human constructions negatively impact coastal ecosystems

Not surprisingly, humans are likely at least partially to blame. When the researchers looked at satellite images of the areas, they were able to come up with possible explanations for the dieback. Natural changes in topography can impact water flow through an area and make it harder for mangroves to regrow.

However, coastal communities should take note: The team also found that human-made obstacles such as roads and levees also altered water flow and have an impact on these crucial mangrove ecosystems. These features of the built environment restrict or even stop water from flowing between previously connected areas—and this can have a range of devastating knock-on effects. 

Human constructions increase the length of time for which floodwater remains on the surface. This can degrade the fine root systems of trees and other plants within the ecosystems. Pooling of brackish water can also lead to increasing salinity where water has been held back. Elsewhere, areas are also artificially kept dry, which can also lead to increased plant stress for those ecosystems too. 

Wetland vegetation—so crucial for a huge range of reasons—thrives in more stable conditions and human-built features can reduce their ability to bounce back. 

Take-aways for coastal communities

This study is yet one more wake-up call to coastal communities, highlighting the importance of very careful planning when it comes to construction in and near these delicate coastal wetlands. Building flood prevention barriers and levees may be short-term solutions for flooding issues. But its impacts on the natural flood defensive ecosystems could mean they worsen problems significantly longer term. 

Long-term planning for storm preparedness and flood defense must embrace and protect the natural environments along the coastline. Everyone needs to recognize just how much we all depend on the natural ecosystems around us, and just how much can be lost if we do not act, and act fast, to remediate damage and preserve the natural ecosystems upon which we all rely. 

Coastal communities must better understand the interrelations between the natural and built environment and the impact of geology and plant life on the severity of storm effects. The study suggests that adding new metrics to the traditional hurricane rating system to account for storm surges and geology could help. 

The researchers also suggest establishing field research stations in low-lying areas so that the biological and physical processes in these vulnerable areas can be better understood. Another strategy they suggest for coastal resilience is regularly performing remote sensing surveys to monitor drainage basins and identify areas where water connectivity should be improved. Where things can be improved, the study also suggests new tidal channels should be created to improve freshwater flow. 

"What we have learned in Florida can be useful to North Carolina and other coastal regions," said David Lagomasino, lead author of the study, in a statement. "Our results indicate that the elevation of the landscape, the connectivity of water across the landscape, and the height of storm surge can indicate vulnerable areas. In other words, low elevation areas that are disconnected or do not have the capability to drain after being flooded are more susceptible to long-term damage."

"This is useful for understanding the resilience of coastal forests and wetlands in North Carolina and may also be important in predicting urban areas that may also be less resilient to these extreme events."

By looking more closely at coastal ecosystems, and taking steps to protect them, coastal communities can boost resilience, remediate existing damage, and prevent much potential further damage in the future.