Nature Notes

By Larry Penny

With all of this rain the vegetation is as lush and green as it's ever been, leastwise in the writer's recollection. After three droughty years, we might have guessed that we'd get a monsoony one. It's a real gusher.

The perched water table in Montauk has reached record heights, Georgica Pond has filled to the brim faster than in any previous year. The forest of East Hampton's Northwest is beginning to look a lot like the forests of the Pacific Northwest. It's not out of the question to fashion a temperate rain forest out of an eastern deciduous one; you just need a lot of rain during each growing season for several years running. It could happen here.

There is only one kind of vegetative cover locally and along the Atlantic Coast that is not dependent on the amount of annual rainfall. It grows lush and green whether the climate is wet or dry. This cover, of course, is the salt marsh, a form of prairie or grassland, that derives its water from the daily tidal inundations. It's a grassland because its dominant plants are grasses.

South of Georgia and along most of the Central and South American coasts, mangrove trees tend to be dominant, thus tidal marshes as we know them are sporadic and rare. We don't have trees in our tidal wetlands; those that try to gain a toehold such as the eastern red cedar are doomed to fail.

Next to the grasslands of middle America, the veldts of Africa and the steppes of Asia, the coastal grasslands of the Atlantic Ocean are the most capacious. And they're the only sizable ones that are drought resistant. As long as the earth rotates around its axis, continues to circle the sun, and the moon remains in orbit around the earth, there will be tides, and there will be tidal grasslands along temperate coasts.

These tidal grasslands are relatively modern inventions. It took a while for grasses to evolve and get the hang of tolerating salt to the point where they could not only withstand its osmotic forces, but could actually thrive in it. Grasses are the most prolific of all plant species and only a few of them have figured out how to grow in salty substrates.

The most successful of these in our clime is saltwater cordgrass, Spartina pectinata. It can actually grow with its roots submerged in seawater throughout the entire flood tide cycle, which, on our coast, occurs two times a day. (Eelgrass also grows along our coast in saltwater, but it is not a grass.) In southern salt marshes, saltwater cordgrass reaches four to six feet in height before flowering, and in Long Island marshes only about three feet. Whatever point the average flood tide reaches each day in protected embayments, and occasionally on the open coast, you will find cordgrass outcompeting the other species there, with few exceptions.

Landward of the saltwater cordgrass another spartina is found, salt marsh hay, Spartina patens. It was so abundant in colonial times that it was used to feed livestock, as insulation in houses, and as a garden mulch. It was cut at the end of summer, "ricked" in big piles, then transported in wagons to dry storage in barns and sheds for winter feeding and other uses. The upper edge of the salt marsh is generally fringed with groundsel bush, sometimes called sea myrtle, and occasionally with switch grass.

Just as the prairies support prairie dogs, badgers, black-footed ferrets, dickcissels, lark sparrows, prairie chickens, and a host of other animal species, the salt marsh community is equally diverse and interesting. Herons, glossy ibis, egrets, willets, oystercatchers, sharp-tailed sparrows, seaside sparrows, rails, fiddler crabs, marsh snails, marsh crabs, muskrats, and diamondback terrapins are some of the species regularly seen in and around salt marshes. Without the vegetation dominated by the two keystone species, salt marsh cordgrass and salt marsh hay, the ecological community would be decidedly different.

Salt marsh grasses are exceedingly productive, as productive as conventional hayfields. But they can easily be harmed. Two acts of nature that cordgrass does not tolerate are the repetitive lapping of largish waves and the scraping-shearing action of sea ice. You never find cordgrass growing on the ocean shore, and rarely on exposed outer bay shores, where waves and ice shearing are the most prominent. The combination of waves, tides, and sea ice is very tough on cordgrass stands; it literally bulldozes them away.

Because it grows higher up on the marsh, salt marsh hay is more resistant to these destructive forces than cordgrass. Even in the quieter embayments ice can do damage, especially by repeatedly freezing and thawing, which sloughs off sizable chunks of marsh peat, the "soil mixture" that most cordgrass grows in.

For the long term, sea level rise also presents a threat. If the salt marsh species can't retreat as quickly as the water rises, they stand to be done in by drowning. At the present rate of rise, we could see all of our local salt marshes underwater by 2050.

Human acts can also be injurious to stands of spartina grasses. Walking in the same spot over and over compresses the peat and tramples the grass. Spartina turf is not resistant to repeated passovers the way golf course and lawn turf is.

In the recent past, the human act most destructive to wetlands has been the filling of them. Long Island tidal wetlands were routinely used to receive sands and muds hydraulically dredged up to create navigation channels in coastal bays and harbors throughout the first two-thirds of the 20th century.

A large portion of Long Island's historic coastal wetlands was covered in this way, frequently under the aegis of the United States Corps of Army Engineers, often underwritten with federal, state, and county funds. We gained a marvelous intercoastal waterway, but at the expense of losing half our wetlands.

In 1973 this practice of filling and covering came to a halt when the New York State Legislature passed the Tidal Wetlands Act. It was implemented shortly thereafter, and since then very few wetlands have been lost to questionable practices of the past. Prior to the act's passage, hundreds and hundreds of acres of tidal wetlands were being destroyed by human activities each year. Since then, only a few acres have bitten the dust. And those acres that are filled or damaged since the passage of the law are in almost every case restored.

In San Francisco Bay, tributary to the Pacific Ocean, it wasn't dredge spoil that did in the marshes, it was garbage from municipalities situated along the bay's sides. In other words, the marshes were used as cheap landfills and as a way to create developable land for shoreside developments. This practice also came to a halt. In fact, at about the same time we began protecting New York State wetlands from such desecration.

A second practice ubiquitously employed in the 20th century in Long Island salt marsh areas, and elsewhere along the coast, also played havoc with these marshes. Marshes that were not filled over were crisscrossed with ditches. These ditches were dug by hand in the 1930s with support from the federally sponsored Works Progress Administration, and later by ditch-digging machines used by county public works departments. Hundreds of miles of these ditches were dug throughout Long Island marshes. The rationale was mosquito control.

Mosquitoes are vectors for several diseases such as equine encephalitis, dengue fever and malaria, and, now, West Nile virus. Consequently, the ditches came to be called "vector control" ditches. It is doubtful that these gridwork lattices effectively reduced mosquito problems, but they did put people to work. When DDT became available in the 1940s it proved to be a far more effective control. Today the biological agent Bt is widely employed in place of the hard stuff.

There are about 40 miles of vector ditches in East Hampton Town marshes. Northwest Creek and Accabonac Harbor are the most extensively ditched. The ditches may limit the breeding of mosquitoes to some extent, but they also drain the tide off the marsh prematurely during each flood tide.

This is harmful to marsh species, especially salt marsh cordgrass. It is also harmful to salt marsh hay and other salt-tolerant species, such as spike grass, salicornia, black grass (a rush), marsh elder, salt marsh gerardia, sea lavender, sea-blite, salt marsh plantain, and salt marsh aster, which, taken together, largely make up the unique upper Atlantic Coast salt marsh community.

There is one marsh plant, a species of grass, however, that loves ditching. If it were not for ditching it wouldn't have become such a problem throughout Long Island. That species is ditch reed, or Phragmites communis. It occurs the world over. The writer remembers coming across it in the middle of a Papua New Guinea rain forest in 1987. There are perhaps hundreds of strains or genotypes of this cosmopolitan species.

The local ones have pretty much disappeared, as demonstrated by the recent gene matching work of Kristin Saltonstall at Yale University. A foreign strain from Europe has taken over this coast from the Canada Maritimes all the way to Florida. It's aggressive and vigorous, and the local salt marsh plants, especially the upper marsh plants such as salt marsh hay, are no match for it.

The ditching of the marshes has facilitated this alien ditch reed's entry and takeover. Phragmites doesn't like saltwater, but it can invade ditched marshes because the saltwater drains from the marsh via the ditches so quickly.

Phragmites sends out underground rhizomes 20 or more feet from a land base. It pumps freshwater out through these "pipelines" to its seaward stalks, which take hold and become established, particularly where tidal flooding has been minimized because of the ditches. The rich complement of wading birds, crabs, and other salt marsh species is not to be found in the middle of a phragmites tangle.

Phragmites grows six to 12 feet tall and shades out the other more interesting salt marsh species. It also steals their nutrients and crowds out their roots. In East Hampton, the tidal wetlands attendant to Northwest Creek and Accabonac Harbor are the most overgrown with phragmites. It is not by chance that these two water bodies are the ones that are the most ditched: Northwest Creek has 16 miles of ditches, Accabonac Harbor, 17 miles. There is definitely a causal relationship between phragmites success and ditching.

There may also be a causal relationship between phragmites and eelgrass, but if so, a much more arcane one. Of all East Hampton tidal tributaries to the Peconic Estuary, eelgrass has become the sparsest in Northwest Creek and Accabonac Harbor. Hog Creek, which has suffered the least at the hands of phragmites and has almost no vector control ditching, has the biggest crop of eelgrass of all.

You figure it out.