"The effect of traffic on the beaches is significant," said Jacqueline Steinback of East Falmouth, Mass., who studied the creatures living in and around the wrack -- the vegetation that accumulates at the high tide line -- on the beaches of the Cape Cod National Seashore.
"Scientists originally thought that driving on beaches wouldn't have much impact since beaches are constantly changing and the species are already surviving waves, winds and extreme temperatures. But traffic is still having an effect on certain species," she added.
Funded by the National Park Service, Steinback's research compared the composition and abundance of beach invertebrates living in and around the wrack on beaches with and without vehicular traffic. She took core samples, set pitfall traps, and collected wrack samples on three beaches at the Cape Cod National Seashore -- Race Point North, Race Point South, and Coast Guard Beach in North Truro.
On beaches where traffic was permitted, the number of animals tallied was from 30 to 50 percent lower than on beaches where traffic was prohibited.
"The wrack line is where a lot of insects and crustaceans congregate and live," she said. "Birds and other scavengers pick through it. It's an important part of beach ecosystems."
The wrack is used in many different ways by different animals. For instance, many creatures use it as both food and cover from predators and extreme temperatures; several species of flies use it as a site to lay their eggs; and wolf spiders migrate back and forth from the beach grass to the wrack to feed on small crustaceans called amphipods.