Floating Wetlands

Baltimore Harbor’s Floating Wetlands

If you have sailed or powered into Baltimore Harbor or been walking along the waterfront, you might have noticed small islands floating along the shore line. Some are in front of the World Trade Center and others next to the National Aquarium. More have been proposed and are awaiting approval.

The waterfront looks very different than it did two hundred years ago. Now it is all pilings and concrete and a very artificial man-made environment. Back then, there would have been tidal wetlands lining most of what is now the inner harbor, as well as the outer harbor which is now docks for freighters and other large ships. In fact now, it is almost impossible to tell that it is part of an ecosystem and part of a river. It looks more like a dirty Disneyland.

To try and replace some of the ecosystem effects of a tidal wetland, these floating platforms have been built. They are built with buoyant materials so the weight of the growing plants won’t sink them. They are planted with different wetland grasses including saltmeadow hay, saltmarsh cordgrass and marsh hibiscus.

A number of different companies make these floating islands. The one by the aquarium is made by Biohaven Floating Islands and is 200 square feet which sounds large but is only 10 x 20 feet. Others were designed by Biohabitats and students at the Living Classroom Foundation helped to build them.


Despite their relatively small size considering the large quantity of tidal wetlands that have been lost due to development, they provide habitat enhancement and some improvements to water quality. A number of animals have been seen in, on and around the islands including otters, eels, blue and night herons as well as ducks. Insects and birds  perch on and hide in and generally use the plants for habitat.

Not only do grasses grow on the top but barnacles, mussels, and a variety of other plants and animals grow on the underwater portion. Also, the roots of the plants that stick down into the water and the island itself provide by shelter and shade for fish, crabs and other creatures. The general scientific term is nekton which is any marine organism which can move and includes everything from the microscopic to whales. (Obviously the islands are not going to attract whales.)

The barnacles and mussels are filter feeders and help clean the waters. The roots of the plants also absorb nutrients and remove them from the water. This includes heavy metals although due to the  size of the islands and the fact that is an open system it doesn’t have as much impact as if it was a closed system.

There are plans to add more of these islands but the best way to clean up the river is to control runoff at its source. Most of the trash and pollution in the river come from runoff. Despite the islands small ecological impact, they are very important as an educational tool. They are in very public places and help people realize that what they do on land has an impact on the water.