On July 26, L.K. Thomas, research biologist, shared his comments and some of his academic work on Dyke Marsh Wildlife Preserve and its restoration. He began to study Dyke Marsh in 1959 and has published many papers on various aspects of this freshwater, tidal wetland. He has visited Dyke Marsh many times, including forays wearing hip boots and chest waders.

Thomas began his career with the U.S. National Park Service as a ranger naturalist in 1953 and retired in 1998 as a resource management specialist. He has an extensive background in ecosystem ecology, hydrology, resource management, wetland ecology and management of exotic species.

Here are some highlights of our conversation:

• “Dyke Marsh is the only temperate, Pleistocene, freshwater,
  tidal, climax, narrow-leaved cattail (Typha angustifolia) marsh, not only in the national park system, but in the world. ... It should be recognized as the Temperate Pleistocene Marsh National Monument,” he has urged NPS. A national monument can be designated by the president or by Congress. According to the NPS, a national monument is “intended to preserve at least one nationally significant resource. It is usually smaller than a national park and lacks its diversity of attractions.”
• “Freshwater tidal marshes are rare. . . this unique marsh is in grave jeopardy,” Thomas said.
• “The scour is an essential part of this ecosystem and is responsible for Typha angustifolia being uniquely climax in this marsh ...  the scouring processes need to be restored.” The Haul Road and the marina prevent scouring needed by the marsh, he said. An elevated boardwalk would allow scouring and “normal water flow” and provide pedestrian access. Scouring can remove some invasive species.
• “Pleistocene sediment was deposited in what is now Dyke Marsh.”
• The narrow-leaf cattail “is never allowed to succeed to another vegetation type because of periodic scour by the flooded Potomac.”
• “The muskrat is the keystone species in this marsh. Its function “is to weaken the cattail mat by its tunnels, canals and feeding.
• Thomas and several colleagues presented a plan for restoring Dyke Marsh to congressman John Dingell in 1964. (Dingell is the author of the 1959 law that added the Dyke Marsh to the national park system.) In his 1964 memo for the record, Thomas wrote that the congressman was concerned that “the filling of the area was not progressing rapidly.
• Restoration should include placing coarse sand and fine gravel at the edge of the Pleistocene sediment.
• If restoration involves planting, plant as nature would plant, thick enough to get natural thinning.
• “Hunting Creek is the key,” he said. At one time, “a lot of water was coming down from Great Hunting Creek/Cameron Run” and depositing sediment into Great Hunting Creek Bay to form the floodplain, he said. The flow is now constricted by the culvert of the George Washington Memorial Parkway.
• Ships once dropped their ballast in what is now Dyke Marsh, some of which was bricks.
• “The restoration should free up the ecological processes,” he urged.