Tag Archives: National Natural Landmark

Marsh Madness: Restoration of Iona Marsh from Invasive Phragmites

Iona Island, located along an elbow of the Hudson River in Bear Mountain State Park, is technically an archipelago of three islands connected by marshlands. Iona has had many owners in its storied history, prior to being bought by New York State in the 1960s. The Island was host to Native American tribes for thousands of years, who took advantage of the plentiful shellfish along its shores. In the last few hundred years, it has been the site of an unsuccessful vineyard, a hotel and weekend destination for NYC residents, a U.S. Navy arsenal, and a partially built park recreation area. The eastern side of the island past the railroad tracks has been closed to the public since the 1980s, but a small portion of the island consisting of the five remaining Navy buildings is used for storage for the Palisades Interstate Park system. The rest of the island has returned to a more natural state of woods, meadows, and rocky outcroppings and serves as a sanctuary for wintering bald eagles.  The island achieved National Natural Landmark status in 1974, and was designated a NYS Bird Conservation Area and Audubon Important Bird Area shortly thereafter.

A key natural feature at Iona is the extensive marshlands, 153 acres in all, flanking its western side.  Part of the Hudson River National Estuarine Research Reserve (HRNERR), this brackish tidal marsh (marshes with water that has different concentrations of salt depending on the tides) teams with life including fish, waterfowl, waterbirds, plants, and crustaceans. In recent times, the rich biodiversity of the marsh, including a number of state rare species, has been threatened by Phragmites australis, or as it is more widely known, common reed.

Common reed (Phragmites australis) is a plant that was likely brought to the US from Europe and Asia in the 1800s through ship ballast or the water taken in by ships to allow them to balance on long voyages. Commonly referred to as just Phragmites, this non-native plant is invasive in the U.S., displacing and crowding out native plant species, such as cattails, rushes, asters, and many others. In turn, the presence of this species has undermined the complex web of marsh dependent organisms.

The non-native Phragmites is identifiable by its tall stature, dark blue-green leaves, and tendency to form dense stands, with little to no possibility for native species to grow in the areas that they occupy. A native species of phragmites (Phragmites americanus) occurs in NY as well, but this smaller plant with reddish stems grows with less density so it does not crowd out other flora.

Pre20018 Iona
Iona Island Marsh in 2008 before treatment. Phragmites dominate the background.

The phragmites problem at Iona Marsh began in the early 1960s, when the first small colony appeared near a pipe draining into the marsh. Over the next 40 years, phragmites steadily expanded until it covered nearly 80 percent of the marsh area. Researchers tracking these changes noted a concurrent decline in marsh specialist birds and specialized brackish marsh plants, including state rarities.  In an effort to reverse these trends, the Palisades Interstate Park Commission, while partnering with Hudson River National Estuarine Research Reserve and the Highlands Environmental Research Institute, started a New York State Department of Environmental Conservation (NYSDEC) funded management program in 2008 focused on a 10-acre test area. The goal was to reduce the invasive phragmites, and make room for native plants to once again occupy the area. If the program was successful in this small area (1/15th of the marsh), it could be expanded to additional marshlands.

A multi-faceted control and monitoring program has been developed and implemented and the results have been dramatic. More than 90% of the phragmites was eliminated within one year and nearly 97% by the third year. Researchers saw the return of huge meadows of annual native marsh plants, including some state-threatened species, followed by perennial cattail stands. Marsh specialist birds such as Virginia rail, least bittern (State-threatened), and marsh wren followed soon thereafter.  Based on this success, the project was expanded to an adjacent 32-acre area of the marsh known as Ring Meadow. Both areas now have less than five percent Phragmites cover, an overall success on the journey to reestablish native vegetation.

2017 Image
Map of the Iona Island Marsh Treatment Areas

While complete eradication of the Phragmites may be impossible to achieve, success can be maintained through continued monitoring and spot treating remaining and new patches.  Bird and vegetation surveys are conducted annually, as are measurements of sediment build-up on the marsh surface, as it relates to sea level rise.  The goal remains to restore the native plant communities in the marsh to promote biodiversity. A healthy, native marsh community will lead to increased productivity and habitats for fish, birds, and mammals – many of them specially adapted to the brackish conditions at Iona.  With continued management, the long-term outlook is positive for this Hudson River jewel, one of only four large brackish marshes on the Hudson.

RingMeadow
Ring Meadow in 2016. Cattail and blooming Rose Mallow have regrown where phragmites once were.

Interested in seeing Iona Marsh for yourself? While public canoeing and kayaking are not allowed in the marsh itself to protect this unique place, through collaboration with the State Parks, NYS DEC offers free public canoe programs each summer.  Not a fan of getting on the water? Iona Island is accessible by road. There is a parking lot approximately ½ mile onto the island, right before the railroad tracks (the boundary of the public accessible areas), where you can park and view the marsh. Lucky visitors may spot waterfowl, muskrats, frogs, turtles, wetland birds, deer, or even bald eagles!

Photo credit:   PIPC Archives

Dr. Ed McGowan,  2017 Annual Report Iona Island Marsh

Post by Jesse Predmore, SCA

Edited by: Dr. Ed McGowan & Chris O’Sullivan

Featured image: lulun & kame accessed from Flickr

The Ellenville Fault Ice Caves – A National Natural Landmark

The most popular features of the Sam’s Point Area of Minnewaska State Park Preserve are the Ellenville Fault Ice Caves. This remarkable system of crevice caves fills up with ice and snow each winter, and retains some of its ice well into the summer. Even when the ice is completely gone, the caves remain cool all year round. This unusual phenomenon has drawn people to the caves for generations.

Postcard
A postcard from c. 1909 showing the snowed-over entrance to one of the caves. The man in the image is an illustration, and slightly exaggerates the scale.

The significance of the caves has even been recognized by the National Park Service. In 1967, the NPS designated the Ellenville Fault Ice Caves as a National Natural Landmark. This designation is given to natural sites that exemplify the special or unique biological or geological features of a region.

Geologically, the Ice Caves are unlike other caves in the Northeast. Most cave systems are made of limestone, which is easily eroded and dissolved by water. This results in the large, open caverns that most people imagine when they think of caves. The Ellenville Ice Caves, on the other hand, are formed out of extremely hard and insoluble quartz conglomerate. When underlying rock layers were folded by tectonic movement, the hard conglomerate separated along existing joints in the rock.

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Cutaway images demonstrating two forms of crevice cave formation. Source: Jack Fagan, Scenes and Walks in the Northern Shawangunks

The caves remain cold because of the natural refrigeration system that exists within them. When air moves across the top of the crevices, the colder, heavier air sinks down into them. The cold air then becomes trapped in the caves, keeping them at a comfortable temperature even during the hottest days of the summer.

While they received the National Natural Landmark designation because of their unique geologic importance, the Ice Caves have a great deal of ecological impact as well. The NY Natural Heritage Program recognizes the ice cave talus community as globally uncommon and rare in the state and a priority for protection. Because of their cold microclimate, the Ice Caves are home to several species that are infrequent in the region. These include goldthread (Coptis trifolium), mountain ash (Sorbus americana), and black spruce (Picea mariana), among others. Scientists have also taken interest in the presence of a species of cave-dwelling crustacean (Stygobromus allegheniensis) that is only found in four states: New York, Pennsylvania, Maryland, and West Virginia. This little arthropod lacks eyes, as it does not need them in complete darkness. It is also able to survive being frozen, a necessary attribute for surviving winter conditions in the caves.

Espinansa et al. (2015)
Strygobromus allegheniensis. Note the pale coloration and lack of eyes, typical features of cave-bound organisms. Image source: Espinansa et al. (2015)

The Ice Caves have local cultural significance as well. Many residents of the Shawangunks remember the days of “Ice Caves Mountain,” when the Sam’s Point area was managed very differently than it is today. From the late 1960s to the early 1990s, much of Sam’s Point was privately owned and operated as a tourist attraction. Visitors could drive their cars right up to Ice Caves, while a pre-recorded cassette tape described the various features encountered along the way. Doors were placed over the caves to keep the ice inside year-round, and the ice was lit up by multicolored flood lights. A rock wall was built on the cliffs of Sam’s Point to dissuade visitors from getting too close to the edge. While it may have been somewhat kitschy by today’s standards, it cannot be denied that “Ice Caves Mountain” was an important step in allowing the greater public to experience this previously obscure natural wonder.

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Gully with snow at Sam’s Point, photo by Greg Edinger, image courtesy of the New York Natural Heritage Program

Many things have changed since the Ice Caves Mountain days. While Sam’s Point is still managed for recreation, there has also been a large shift in focus towards conservation. Visitors may no longer drive through the park, and the cave doors have been removed in favor of letting the natural ice cycle of the caves take place. Interpretive displays within the park focus on the natural history of the caves, rather than just their physical spectacle.

While National Natural Landmark status highlights the importance of a site, it is up to the owners of that landmark to manage and protect it. Fortunately, Sam’s Point is part of a Park Preserve, meaning that all of the plant and animal life within it is protected. As such, those who appreciate the cultural, geological, and ecological significance of the Ellenville Fault Ice Caves are able to experience them to the fullest extent.

Tim Howard, NYNHP
Ice and trees in leaf – a late spring exploration of the ice caves. Tim Howard, NYNHP

Want to explore the Ice Caves? State Parks staff offer guided hikes to both Shingle Gully and the Sam’s Point Ice Caves; click here for the Sam’s Point Area calendar of events.

References:

Fagan, Jack (2006).  Scenes and Walks in the Northern Shawangunks (3rd Ed.). Mahwah, NJ: The New York-New Jersey Trail Conference.

Espinasa, L., McCahill, A., Kavanagh, A., Espinasa J., Scott, A., Cahill, A. (2015).  A troglobitic amphipod in the Ice Caves of the Shawangunk Ridge: Behavior and resistance to freezing.

NatureServe Explorer Allegheny Cave Amphipod

Ice Caves Talus Community Conservation Guide

Featured image courtesy of Mike Adamovic, from Ice Caves of the Shawangunk Ridge

Post by David Hendler, SCA Education and Stewardship Intern