Restoring Hydrology to Salt Marshes along the Narrow River
Salt marshes on the Atlantic coast are productive ecosystems that contribute to our regional biological diversity and provide numerous ecosystem services to surrounding communities. During migration, these rich foraging grounds support abundant waterfowl, wading birds, and shorebirds that stop over in marshes to help fuel their migrations. The salt marsh sparrow (Ammospiza caudacuta), a tidal obligate species considered at risk of extinction, relies on tidal marshes throughout its entire life cycle. Healthy functioning salt marshes also help improve water quality by filtering stormwater pollution and serve as protective buffers to adjacent infrastructure during storms.
Unfortunately, human alterations have drastically changed the ability of these ecosystems to function naturally, both along the Narrow River and throughout New England. Beginning in colonial times, farmers dug drainage ditches and built embankments in salt marshes to increase the yield of saltmeadow cordgrass (Spartina patens) for “salt hay” to feed livestock. During the 1930’s, almost all of the marshes on the east coast were drained to control mosquito populations through extensive grid ditches. These changes altered the natural hydrology of these systems, and over time, resulted in the formation of shallow standing water on the marsh surface, vegetation die off, and marsh subsidence. More recently, salt marshes are threatened by more intense and frequent flooding, due to climate change and accelerated sea level rise, exacerbating these issues as marshes drown in place.
Over 39% of current salt marsh habitat along the Narrow River is dominated by a mixture of stressed vegetation and bare pans, typical of degraded marsh conditions. This is particularly concerning for rare and declining species such as the saltmarsh sparrow that rely on vegetation that cannot tolerate excessive flooding such as saltmeadow cordgrass, which saltmarsh sparrows depend on to build their nests. By the end of the century, sea level is predicted to rise by as much as 3 feet, leading to substantial losses of the remaining salt marsh habitat, unless we help.
In 2015, The U.S. Fish and Wildlife Service received Hurricane Sandy Disaster Relief funds to complete an ambitious restoration project designed to improve the health and resilience the Narrow River’s salt marshes. A technique developed by Save the Bay known as runneling was used to address poorly drained marsh surface areas from Pettaquamscutt Cove to Lacey Bridge, including several of the properties owned by the Narrow River Land Trust. A runnel is a shallow channel, no more than 12 inches wide by 12 inches deep, that is dug either by hand or by a low-pressure excavator. Runnels help drain the impounded water from the marsh surface, relieving water stress, and allowing vegetation to recolonize the degraded areas. Once established, vegetation helps rebuild marsh elevation by catching sediment and building up organic material, a process known as accretion. The lessons learned from this work will help to inform future marsh restoration projects throughout the state and New England and help to conserve this vital habitat for wildlife and future generations.
Cottontail Habitat Restoration
Land Trust’s Role Includes Actively Managing Habitat
“We know the population of the New England cottontail rabbit has fallen rangewide,” says Gary Casabona, a USDA Natural Resources Conservation Service (NRCS) biologist based in Warwick, R.I. “Here in Rhode Island, the species’ decline has been especially dramatic. It’s also been hard to quantify, thanks to a lookalike rabbit, the eastern cottontail, that’s also found across the state.”
The eastern cottontail was introduced to Rhode Island and much of New England around 85 years ago as a game species to be hunted. “Since it’s so hard to tell eastern from New England cottontails visually,” Casabona explains, “conservationists often must rely on DNA analysis to confirm the presence of New England cottontails in a given area.” During winter, wildlife biologists and volunteers go into likely habitat areas and look for rabbit tracks in the snow. Says Casabona, “They also find and pick up rabbit fecal pellets, or ‘scat,’ and store them in a cooler so the DNA in the scat doesn’t break down.” The samples go to the University of Rhode Island’s Conservation Genetics Laboratory, where DNA testing reveals whether eastern cottontails or New England cottontails deposited the pellets.
“Five scat samples have proven to be from New England cottontails in Rhode Island over the last several years,” reports Casabona. “After verifying a population on the ground, the next step is to provide enough feeding and hiding cover in or near the occupied area so that the local cottontail population doesn’t decline further or even vanish.”
In 2013, members of the board of the Narrow River Land Trust (NRLT) approached Casabona. They were interested in making some young forest – prime New England cottontail habitat – on their land, specifically on a tract called the Viall Property, Washington County, a mile west of the shore of Narragansett Bay. As an NRCS biologist, it’s Casabona’s job to help plan and ultimately fund such habitat-creation projects. “I was incredibly excited,” he says. “The land they were proposing for management was only about a mile away from one of the sites where biologists had recently found scat samples from New England cottontails.” That meant the site was within dispersal distance, and the native rabbits might spread into any newly created habitat.
Finding the Right Place to Make Habitat
Casabona worked with NRLT board members Julie Sharpe and Rob Macmillan to identify two adjacent areas totaling 19 acres that could be managed to help cottontails. “The idea was to cut down mature forest so that it would come back thickly, with plenty of young sapling trees sprouting from the stumps, along with shrubs such as blackberry, raspberry, blueberry, and greenbriar. Rabbits need these types of habitats for dense hiding cover, which protects them from predators, and to find winter food – they eat the tender twigs of young saplings and shrubs when green plant food is unavailable.”
There was just one problem, and it was a big one: Other land trust members, many of whom were birdwatchers, weren’t sold on the concept that cutting down trees could be good for wildlife. Says Sharpe, “The biggest challenge for the land trust was explaining to our members and neighbors the rationale for cutting trees that to them were perfectly healthy, well-loved, and admired.” As land trust members, “some people felt that the trees had been entrusted to us into perpetuity and that cutting them was a violation of that trust.”
Continued Sharpe, “In order to succeed, we had to stay in front of the story and use our work as an opportunity to engage our community in a deeper understanding – not only of how our forest and species diversity has in fact changed over time, but also of how the role of a land trust calls for our ongoing attention and active management.” The NRLT board invited Casabona to give a talk on the subject during one of their membership meetings. Casabona explained to his audience that Rhode Island already has many large areas of mature forest, while “shrubby young forest with dense vegetation at ground level has dwindled over recent decades.” He noted that such habitat arises in a forest following a disturbance like a hurricane, a wildfire, or a clearcut timber harvest. In the absence of hurricanes and wildfires, “Humans need to step in,” Casabona says. “Without active management, the understory of shrubs and other plants in a forest will die out, disappearing in the shade cast by a mature forest. And it’s those dense plants that New England cottontails and a whole suite of other wildlife need to survive.”
Communicating a Key Concept
Many birds that breed in young forest have had sharp population declines in the Northeast and in Rhode Island in recent decades, including American woodcock, prairie warbler, blue-winged warbler, brown thrasher, eastern towhee, field sparrow, and whip-poor-will. Creating new young forest on the Narrow River Land Trust property would provide new potential breeding habitat for these beleaguered species.
“When I told the audience that these areas would also provide highly nutritious fruits needed by migratory songbirds during their fall migration,” Casabona recalls, “I could see they were starting to grasp the importance of this type of habitat enhancement and its benefit to a whole lot of animals in addition to rabbits.”
With support from the land trust membership, the project moved forward during the winter of 2013. “The management project can probably be best described as a seedtree cut,” says Casabona, “where most of the mature trees were cut down but a number of trees per acre were left standing.”
“The trees to be left were identified and marked before the cut started,” says board member Rob Macmillan. “We tried to leave trees that provided some type of benefit, such as white oaks with good crowns for producing acorns, or trees with cavities that could be used by cavity-nesting birds.” NRLT and Casabona made the local logging contractor, Miller Firewood & Logging, aware of the goals of the project before cutting got underway. Macmillan says the company did a thorough, competent job: “They cut many unmerchantable trees, avoided driving over the cut treetops, and spread them out over the site whenever possible. We asked them to leave several larger logs per acre for wildlife use, and they also constructed brush piles for wildlife cover.”
The large amounts of woody material left on the ground will provide habitat for salamanders and snakes before they eventually break down, cycling nutrients back into the soil. The cut treetops also act as a physical barrier and help deter deer from browsing on sprouts from the cut stumps. The stump sprouts, in addition to being the source of a new forest, also provide food for rabbits. Notes Casabona, “Without the shade of the large trees overhead, sunlight now can reach the forest floor, and the blueberry, huckleberry and other understory plants are growing in lush, providing resources for rabbits, birds, and other kinds of wildlife.”
“It’s been a positive experience working with the professionals from the local NRCS office,” says NRLT’s Macmillan. “They’ve been very enthusiastic about the project and continue to be involved and interested even after the on-the-ground work has been completed. Besides the focus on New England cottontails, they have also conducted several bird surveys and are already planning a site visit to assess the regenerating vegetation next spring. We look forward to watching the changes that take place on the site over time and hope the NRCS will continue to help monitor the work that has been done.”
Partners and Funding
Narrow River Land Trust, University of Rhode Island Conservation Genetics Laboratory, USDA Natural Resources Conservation Service, Wildlife Management Institute
Deer Hunting Program
The Narrow River Land Trust recognizes that hunting is a valuable wildlife management tool. White-tailed Deer (Odocoileus virginianus) is a naturally occurring species in Rhode Island. However, because of their high reproductive rate and the lack of sufficient predator control, high numbers of white-tailed deer cause damage to native vegetation and thereby negatively impact the conservation values of protected properties.
Deer hunting is allowed on selected Narrow River Land Trust -owned properties according to guidelines established by NRLT, informed by the current RI DEM wildlife management practices. Each hunter annually reports data regarding deer that have been seen and taken, which is reviewed and analyzed for wildlife management purposes.
Please see the NRLT hunting requirements for more information.
Tree Planting at the Benson Preserve
How can an introduced moth, a fungus and weather interact to alter a walk through the woods at the NRLT Benson Preserve?
Oak trees are a keystone species in many parts of southern RI, forming a dense canopy that alters the light, temperature and moisture environment for understory plants that live below the usually dense forest canopy. Oak trees have filled this role on the Benson Preserve – until recently. In the summer of 2016, an especially large population of invasive spongy moth (Lymantria dispar; formerly known as the European gypsy moth) caterpillars fed on oak tree leaves, defoliating the canopy. Simultaneous with the spongy moth caterpillar boom, the summer of 2016 was much drier than normal which hindered the ability of the oak trees to grow new leaves. The combination of predation and drought resulted in the death of many oaks throughout RI. On the Benson Preserve dead oaks are especially prevalent on the top of the glacial ridge as one walks east up-grade from the Narrow River. The soil at the top of the ridge tends to be drier and nearly all the red and white oaks in this area died following the 2016 caterpillar infestation and drought. So many oak trees had died in this area that the Land Trust hired a professional forester to fell the standing dead oaks so that they did not present a hazard to hikers walking below.
A keystone species
In Rhode Island, as in much of New England, Quercus spp. (the genus oak trees are classified in) has been described as a keystone species, because so many other species depend on these trees. In a recent book “The Nature of Oaks,” University of Delaware entomology professor and conservationist Douglas Tallamy described oaks and other native trees such as maples and pines as keystone plants, like the keystones in Roman arches.
“In place,” Tallamy wrote, “the keystone supports all the other stones in the arch but take the keystone away and the arch collapses.”
Many of those keystone oaks at the Benson Preserve, and regionally, are now dead, killed by severe spongy moth caterpillar infestations that began in 2016 and continued, to a lesser extent in recent years. Already weakened by drought and the stress of repeated caterpillar defoliation, the trees that comprised the forest canopy succumbed, leaving stands of dead timber. Once the oak-dominated canopy was lost, fast growing understory plants such as greenbriar that were formerly light-limited by the shade-providing oak canopy began to dominate the landscape. This is evident on the northeastern-most trail on the Benson Preserve. Once the mature oaks were dead, the source of ‘mast’ or acorns to repopulate the area with new oaks also was gone, effectively changing the plant community composition and ecology of the area.
In April 2021 the NRLT embarked on an oak tree planting program at Benson Preserve to hasten the recovery of the oak canopy. Dozens of native white oak (Quercus alba) seedlings were planted on the eastern portion of the Benson Preserve. The seedlings were planted with temporary blue plastic tubes around them to help locate the seedlings and to protect the young trees from predation. Three years later approximately two-thirds of the young white oak trees have survived and are now at least double their original planting size. It will be a while before these trees reach maturity, but the Narrow River Land Trust considers, and is planning for, environmental change and long-term stewardship of the conservation lands it manages.