The Nature Conservancy. Protecting nature. Preserving life.™

Brown Pelican, Loggerhead Key, Dry Tortugas National Park. © Ross Geredien

What kind of birds use the bird stakes?

It varies by season. In the spring and summer, brown pelicans are dominant in the Perdido Bay area. In the winter it’s the double-breasted cormorant. But other birds use the roosts as well, including gulls, terns, herons and egrets.

Seagrass beds, sometimes called “the prairies of the sea”, span hundreds of thousands of acres in the Gulf of Mexico. Here in Florida, we enjoy some of the world’s best. 

These vast fields of green are underwater meadows that:

• Protect water clarity,
• Dampen wave action,
• Prevent shoreline erosion,
• Provide food and shelter for juvenile fish and shrimp, and
• Offer habitat for manatees, sea turtles, and sea horses.

But seagrass beds are dying at an alarming rate – reduced as much as 90 percent in some bays across the Gulf. The Conservancy is determined to reverse that trend, and is experimenting in Florida with techniques that may prove helpful around the world.

“Every acre of seagrass that we lose is a big blow to native species that depend upon that habitat,” says marine scientist Laura Geselbracht, who directs the Conservancy’s work in Florida. “One acre can support as many as 40,000 fish and 50 million invertebrates.”

The main danger? A thousand cuts

Because seagrass beds primarily occur in very shallow water, they are vulnerable to damage from motor-driven boats. And what a boat propeller does in 5 seconds may take from 5 to 50 years to heal!

By tearing up sand and ripping out grasses, a boat propeller can gouge holes and make long trails through the seagrass. These are called scars because they look remarkably like pale scars when viewed from the air. One or two scars can heal themselves, but constant small cuts will gradually overwhelm a seagrass bed’s ability to recover.

Testing simple and effective solutions

The Conservancy works in several Florida locations to:

• Restore previously damaged seagrass beds, and
• Prevent or minimize future damage from motor-driven boats.

In 2009, scientists began experimenting with two primary restoration techniques. One technique used effectively in northwest Florida is elegant in its simplicity – well, if a technique involving PVC pipe, galvanized screws and bird poop can be called elegant. But what this method lacks in dignity, it makes up for in effectiveness.

Where the poop comes in

Pioneered in the Florida Keys, where more than 600 boat groundings are reported every year, a “bird stake” technique is quite straightforward:

• Fashion two pieces of durable PVC pipe into a rough T suitable for a bird roost.
• Place the bird stake directly over a seagrass scar.
• Let nature takes its course.
• Remove the stake once healing has taken place.

Bird poop (also known as guano) is high in phosphorus – an important nutrient for seagrass growth. Studies from the Keys have shown that the re-growth of seagrass is more rapid when propeller scars are heavily fertilized by birds. Bird stakes appear less expensive and more successful than some other, more intensive techniques.

Sediment tubes fill the trenches

A second seagrass restoration technique uses 3-foot long, sausage-shaped, cotton fabric tubes. Filled with sediment and placed in boating scars, sediment tubes been used by the Conservancy in the Crystal River area. The fabric degrades in about one year, while seagrasses send out rhizomes or root-like structures that re-colonize the area.

Charlotte Harbor, a significant southwest Florida estuary, has significant scarring of seagrass beds near commercial marinas. There, the Conservancy will compare the effectiveness of the two techniques.

“These experiments are significant,” says Geselbracht. “We plan to test the two procedures against each other and against nature at Charlotte Harbor to see which works better and under which circumstance.”

Final piece of the puzzle: Educating boaters

To prevent further damage, the Conservancy is engaging the boating community by:

• Carefully marking boat channels
• Placing signs at boat ramps reminding boaters to be careful in shallow water, and
• Educating boaters about the ecosystem services that seagrasses provide us all.

Thanks to our partners

We couldn’t be successful without our partners. Especially in marine habitats, where the Conservancy is by law unable to purchase the area we wish to protect, effective zoning is very important.

Special thanks to:

National Fish and Wildlife Foundation
Shell Marine Habitat Program
National Oceanic and Atmospheric Administration