Simply put, a dune is a hill or ridge of sand piled up by the wind. Already bored? Well you shouldn’t be, because when it comes to sand dunes, there’s a lot more than meets the eye. As with so many things in the natural world, dunes, though deceivingly bland on the surface, contain multitudes of complexities: a rodent constructs an elaborate tunnel system, crickets and frogs dive inside to evade predators, opportunistic sea oats take root and hold on tight. And all the while the dune grows, one grain of sand at a time. You’ve certainly seen the rolling mounds at the beach, surrounded by protective fencing and threatening signage, but have you ever stopped to wonder what all the fuss is about? Here’s the deal on dunes.
WITH THE WIND
Sand dune systems are formed by wind action. It all starts with some sort of beach debris, such as seaweed, driftwood, fishing nets, etc. This debris blocks the wind, causing windblown grains of sand to slowly accumulate. Eventually, dune grass seeds find their way to the growing pile of sand and germinate, further stabilizing the ever-growing sand pile. If the initial debris was rotting vegetation, like seaweed, its nutrients will even help the new seedlings to survive. Congratulations, Mr. and Mrs. Beach — it’s a dune!
Although the origin of the word “dune” is somewhat unclear, some suggest it comes all the way from the Gaulish word “dunum, ” meaning “hill” or “fort.” Though this shouldn’t be confused with the theme music from “Jaws.”
HOME IS WHERE THE SAND IS
Sand dunes are an important habitat for both plants and animals. Besides the beach mice and sea turtles that burrow in, a plethora of plant species put down their roots on the sandy mounds, including sea oats, beach elder, bitter panicum and Gulf bluestem. Without the stabilizing power of these specially adapted plants, sand dunes would not exist.
BRACE FOR IMPACT
Among several positive environmental features, sand dunes are especially useful when it comes to absorbing the energy of violent storms, preventing beach erosion and slowing the process of inland flooding. They’re so important, in fact, that artificial dunes are often created using bulldozers.
CAN I HAVE THE RECIPE?
The three conditions necessary for dune formation include the presence of a large supply of sand, winds strong enough to carry that sand and a suitable location for sand accumulation.
A Sandy Story
- The Perdido Key beach mouse, a small rodent that inhabits the sand dunes of Baldwin County, was declared an endangered species by the federal government in 1985. Their burrows, which usually reach a depth of about three feet, feature an entrance tunnel, a main nest chamber and an escape tunnel designed to thwart predators. Besides the value of their burrows to other dune-dwelling species, beach mice also aid the growth of dune plants by eating and dispersing seeds. Beachfront development, hurricane damage and domestic cat predation are the primary threats to the beach mouse.
- According to Kelly Reetz, a naturalist at Gulf State Park, beach mouse population is a great indicator of dune health. “If conditions within the dunes begin to decline, we will see a decrease in mouse populations. Once conditions are corrected (whether the damage is due to invasive plants, feral cats or foot-traffic), the populations will begin to rise.”
- Each year, Gulf State Park repurposes donated Christmas trees for dune enhancement. “We place three trees together in a horseshoe shape open to the southeast for maximum sand collection,” Reetz explains. “By placing them in strategic locations, we’re able to help new dunes grow and provide a healthy habitat for the Alabama beach mouse, nesting sea turtles and shore birds.”
- The public is asked not to walk on sand dunes because of the destabilizing effect of foot traffic. Just a few footprints can begin the process of dune erosion.
- Act 971, passed by the Alabama Legislature in 1973, is known as the Wild Sea Oats Act and declares it a misdemeanor to pick wild sea oats. In November of 2016, the National Fish and Wildlife Foundation approved a $63 million grant for Alabama coastal projects, $36 million of which will be used to acquire and conserve 2, 700 feet of dune habitat.