Mangroves are coming our way

Warmer weather changing the salt marsh

Black mangroves are moving in on the salt marsh around the bridge headed out to Vilano Beach.
Black mangroves are moving in on the salt marsh around the bridge headed out to Vilano Beach. (Anna Armitage)

JACKSONVILLE, Fla. – Mangroves are spreading northward into north Florida as the climate warms.

Temperature is a critical limit for the plants habitat range which is why the coastal plants are so rare in Duval and St. Johns counties.

Soon the trees that increase fish habitat and buffer fierce storms could change the landscape you often see driving over the local bridges on beach trips. 

The woody plants are encroaching on salt marshes that dominate our area because winters are not as cold. 

When mangroves increase, salt marsh areas decrease. Tall mangrove canopy’s block out the sunlight needed by cord grass shrinking the marsh footprint.

Black mangroves are taking over the barrier island just north of Ft. Matanzas and are spreading quick. 

Mangroves have doubled along the east coast of Florida in last 28 years according to Dr. Ilka Feller, a Senior Scientist at the Smithsonian Institution. She expects mangroves to expand into Georgia marshes by 2060.

St. Augustine and Jacksonville sit in a region that splits the tropical zone south of Cocoa Beach from the colder areas north of St. Marys. This zone, called the Ecotone, historically could not support abundant mangroves. 

Milder recent winters have displaced this historic range up the east coast of Florida.

Freezes between 1940 and 1983 had longer durations and were more severe in St. Augustine. 

The few mangroves that existed in NE Florida have been reduced by dredge and fill of marsh habitat since the 1940’s.

The primary loss in Nassau County occurred during dredging for the Intracoastal Waterway. 

Human activity in Duval County has been more severe with a 36% loss of marsh habitat extending 3.5 miles on either side of St. Johns Inlet and 10 miles up the river.

More mangroves help stabilize the coastline and increase fish habitat. 

Their benefits are so important protection laws limit homeowners from trimming mangroves over 10 feet.  Rules do permit professional arborists with restrictions.

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