Photo: WJXT
“Researchers have observed an increase in mangrove trees in southern Amelia Island, Florida, in recent years. This is well north of the plant’s typical cold-sensitive habitat.
Historically, mangroves have been limited to southern Florida. However, they are now increasing along the temperate zones farther north, from St. Johns to Nassau Counties.
This migration pattern is related to warmer winters and hurricanes. Warmer winters allow mangroves to survive further north, while hurricanes help to disperse their seeds.
A survey conducted by Dr. Candy Feller of the Smithsonian Institute in 2004 found no mangroves along the southern tip of Amelia Island. However, a return visit to the same site in 2017 found mangroves over six feet tall. In May 2023, the same trees had grown to nine feet tall and spread 20 feet wide.
Feller links this expansion to Hurricanes Frances and Jeanie, which hit Florida in 2004. These hurricanes sent wave energy right up the east coast, just when mangrove plant propagation was at peak season. This helped to disperse mangrove seeds throughout the region.
Hurricanes are an efficient mechanism for dispersing mangrove propagules. Thousands of propagules were washed ashore in Northeast Florida after Hurricane Ian in 2022.
Hurricanes are nothing new so why didn’t the plants establish locally decades ago?
The answer is that freezes have kept the species in check. In the past, freezes would periodically kill off mangroves that had migrated too far north…”
— Mark Collins, Meteorologist, News4Jax
Image: A Slide from Dr. Candy Feller’s study showing cycles of hard frosts and hurricanes