Carl Hobbs: The Beach as Habitat
In the introduction to The Beach Book: The Science of the Shore, Carl Hobbs discusses some of the little, frequently hidden creatures that are essential to the health of the beach. Read an interview with Carl Hobbs, or his recent post, Enjoy This Summer at the Beach; It’ll be Different for Your Kids.
We usually do not think of beaches as habitat, as places where creatures live. When at the shore, we notice the other beachgoers enjoying the surf and the seagulls wheeling around in the sky, alert for tidbits to scavenge. But there is other life on and in the beach. Ghost crabs (Ocypode species) are important beach dwellers. They are significant predators and scavengers who excavate burrows that can be as much as 3 feet (1 m) long. Many coastal scientists use the status of a beach’s ghost-crab population as an indicator of the environmental health of the beach. As they zigzag across the beach at speeds up to 6 feet (2 m) per second, ghost crabs provide entertainment for us, especially when our pet dog tries to catch them.
Sea turtles crawl out of the ocean and onto the beach to lay their eggs. Birds like the Least Tern (Sternula antillarum) and the Piping Plover (Charadrius melodus) nest on the beach. Designated a “threatened species,” the Piping Plover nests on the back of the berm near the sand dunes. Resource managers close beaches to use by vehicles to protect nesting Piping Plovers. The Least Tern uses shallow “scrapes” on the beach and in other sandy or gravelly settings.
In The Edge of the Sea, Rachel Carson described smaller animals that live in the beach sand. Sand fleas, any of several small pests that live on the beach, are not insects but are crustaceans that, like their insect namesakes, annoyingly bite our ankles. Most of the beach-dwelling organisms are quite small, often less than 0.04 inch (1 mm) in length. If you think about the harsh physical environment in which they live, you soon realize that they have to be pretty tough, with hard outer-body parts to protect them from being abraded and crushed. Although it may be disquieting to think of all the “bugs” living in our sandy playground, it is good that they are there. They help make the beach a better place by cleaning up the rotting matter that would stink and foul the otherwise apparently clean environment. Even bacteria are important in beach processes. For example, a particular bacterium helps calcium carbonate (calcite [CaCO3]) precipitate out of seawater and bind sand grains together to form beach rock.
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