Florida's iguanas can bring down a seawall

A green iguana can help bring down a seawall without taking a single bite of it. The damage happens underneath. These lizards dig burrows beside seawalls, canal banks, sidewalks, and foundations, removing soil and creating openings that encourage erosion. A structure can lose the ground supporting it because a reptile needs somewhere to hide or lay eggs. That's what makes Florida's iguana problem more than a dispute over chewed flowers. A mostly plant-eating animal can become an infrastructure problem simply by doing ordinary lizard things in an inconvenient place.

Green iguanas aren't native to Florida. Their natural range includes Central and South America and parts of the Caribbean, but escaped and released pets helped establish them in the state. Florida offers an unusually welcoming combination: a climate suitable for many introduced reptiles and a major transportation hub through which animals arrive. Most nonnative reptiles that escape or are released in the United States don't establish breeding populations. Some do, and green iguanas belong to that successful group. Florida isn't their only foothold, either. They've also established populations in Hawaii, Texas, Puerto Rico, and the U.S. Virgin Islands.

South Florida's built environment helps them get around. Its extensive artificial canals act as dispersal routes, connecting places where iguanas can feed, shelter, and reproduce. They're strong swimmers that tolerate both fresh and salt water, so a canal isn't necessarily a barrier. Nearby gardens offer leaves, flowers, and fruit. Females typically reach reproductive maturity between two and four years old and can lay clutches containing 14 to 76 eggs. Their nesting excavations can include interconnected tunnels and multiple entrances. Put food, shelter, waterways, and breeding sites close together, and you've supplied much of what an iguana needs without meaning to.

The appetite matters beyond anybody's flower bed. At Bahia Honda State Park, green iguanas have eaten gray nickerbean, a host plant for the endangered Miami blue butterfly. Its caterpillars depend on host plants for food, and females lay eggs on developing shoots and flower buds. Researchers concluded that heavy iguana feeding deprived the butterflies of food and may have helped drive the park's population to disappear. The iguanas didn't have to hunt butterflies to hurt them. Eating the plant could remove something the next generation needed to survive. That's a quieter kind of ecological damage than a predator swallowing its prey, but it reaches beyond the missing leaves.

There's a human habit underneath this story, too: releasing an unwanted animal can turn a private problem into a shared environmental one. Not every released pet survives, and not every survivor establishes a population. But once a species does establish, its ordinary needs don't stop at a property line. Safe rehoming or surrendering unwanted animals to a wildlife agency avoids adding to that problem. The lesson isn't that green iguanas are villains. It's that moving an animal somewhere it doesn't belong can give its appetite, shelter-seeking, and reproduction consequences nobody intended. Sometimes those consequences include the ground beneath a seawall.