Mangroves are Transforming the Ten Thousand Islands

Mangroves have always been the defining trees of the Ten Thousand Islands, forming storm-resistant forests that stabilize shorelines and fuel fisheries. But today, these same mangroves are pushing inland at a pace that’s startling residents and reshaping familiar landscapes. What once were prairies, marshes, or open views are now becoming dense mangrove thickets — even inside neighborhoods. 

This dramatic expansion isn’t due to mangroves becoming “invasive.”  Instead, it’s a direct response to rising water levels, changing climate conditions, and long-term ecological trends that scientists identified years ago. And the fastest changes are happening right now. 

Why Mangroves Are Appearing Where They Never Grew Before 

Homeowners across Everglades City and nearby islands report the same concerns: narrowing creeks, blocked views, reduced dock access, and root systems spreading into places that were once dry ground. Since Florida law strictly regulates mangrove trimming and removal, managing these trees can be costly and frustrating.  But the trees aren’t acting differently — the environment around them is. 

Floating red mangrove propagules and the seeds of black and white mangroves are riding storm tides and high-water events into swales, drains, marsh edges, and vacant lots. Without regular mowing or functional tide-control valves on the stormwater system, these propagules and seeds establish quietly for years until they become full-sized trees. Several lots in Everglades City are now completely dominated by mangroves, prompting the city to adopt new mowing requirements and initiate efforts to replace tidal backflow valves. 

The Real Driver: Water Levels Are Rising Faster Than Most People Realize 

Most people think of sea-level rise as bigger storm surges or higher high tides. But in Southwest Florida, the biggest change is actually in the low tides — they simply don’t fall as low as they used to. NOAA tide-gauge data from Naples shows that since around 2010, low tides have gradually risen. Even small increases keep marsh surfaces flooded longer. This shift was predicted more than a decade ago. 

 A 2011 scientific study: Sea-level rise and landscape change influence mangrove encroachment onto marsh in the Ten Thousand Islands region of Florida, USA | Journal of Coastal Conservation (Krauss et al.) documented that marshes in the Ten Thousand Islands were already experiencing increased flooding in the early 2000s. (Krauss et al): The study showed that as freshwater flow has changed and sea levels have continued to rise, mangroves have steadily moved upstream and inland, taking over habitat that historically supported marsh-dependent birds. This pattern mirrors similar mangrove expansion documented worldwide. Aside from rare, localized freeze events, very little in recent decades has slowed or stopped this inland migration. 

The long-term study of the vegetation changes in the Ten Thousand Islands National Wildlife Refuge (TTINWR) (Barry et.al.) show just how dramatic the change has been. By analyzing aerial photographs and maps from 1940 to 2005, researchers tracked mangrove stand boundaries from the Gulf of Mexico inland to the refuge’s northern edge. Findings from the study: 

This large-scale shift confirms that mangroves are not simply expanding along shorelines — they are actively replacing marshes, reshaping habitat for birds, fish, and other wildlife. This change has accelerated since 2010 due to the substantial jump in low tides since 2010 and a series of storm surges beginning with Irma in 2017. 

As a result, today we now see marshes and cabbage palm hammocks disappearing and young mangrove forests establishing in once-open prairies. This is exactly the pattern the researchers stated would happen with rising sea levels. 

In places like Shell Island Road in Naples, the evidence is dramatic: standing dead marsh grass, unmoved storm debris, and mangroves now rooting against upland edges that were dry a generation ago. 

Mangroves Have the Advantage — And Prairie Plants Are Losing Ground 

Multiple forces are tipping the balance: 

The result: coastal prairies and marshes across Everglades National Park, Big Cypress National Preserve, Rookery Bay National Estuarine Research Reserve, and the Ten Thousand Islands National Wildlife Refuge are disappearing — not from storms, not from development, but from slow drowning. 

 Before and After: What 15 Years of Change Looks Like 

2010 vs. 2025 — Former Upland 
Areas once dominated by buttonwood and cabbage palms now support carpets of young black and white mangroves. Rings of dead trees mark the old tidal boundary. (See Photo #2: Former Upland) 

 2010 vs. 2025 — Prairie to Mangrove 

Stands of long-dead Sabal palms outline former upland ridges. Their bases are now underwater, filled with mangrove pneumatophores and young mangrove seedlings. (See Photo #3: Prairie to Mangrove). 

These scenes aren’t isolated — they’re appearing across the coastal Everglades. 

 The Takeaway: A Permanent Shift, Not a Temporary Surge 

The Ten Thousand Islands is undergoing one of the most rapid ecological transformations in its history. But it’s not a takeover — it’s nature responding to new conditions. 

For coastal communities, this change brings both challenges and benefits: 

Challenges 

Benefits