Forest Management in New York City

A view of the restored Alley Pond Park in Queens, where volunteers and staff planted both young trees and wildflowers. The site was formerly a vineland. Photos by NYC Parks Natural Resources Group.

There are 10,000 acres of public forest within the five boroughs of New York City. That doesn’t mean street trees, or trees dotting the lawns in parks, but actual forested acres – what are known within the city as forested natural areas. While only a three- or four-hour drive from the southern reaches of what is generally considered the great northern forest, the forests of New York City are a world away in how they must be managed.

The New York City Department of Parks and Recreation’s Natural Resources Group (NRG) is a 23-member team charged with stewarding roughly 7,000 acres of these forests. They are assisted by the Natural Areas Conservancy (NAC), a not-for-profit founded in 2012. Together, the two groups bring a unique mix of horticulture and traditional forestry to the management of this public resource.

Tree-planting, not typically a component of forest management in the northeastern U.S., is a major priority in New York City’s forests. On November 20, 2015, the millionth tree was planted as part of the MillionTreesNYC effort initiated by former Mayor Michael Bloomberg. “With volunteer assistance, more than half of the trees planted as part of MillionTreesNYC were planted in natural areas,” said Kristy King, NYC Parks’ director of forest restoration.

More than 85 percent of those trees have survived, which is impressive given the pressures on trees in urban and high-use environments. The new trees include more than a hundred species of native trees and shrubs, with native seeds sourced from within 200 miles of each planting site. Native genetic diversity is very important to the forest restoration program for a variety of reasons, including the resilience it confers on tree populations.

While forest stewardship is important everywhere, in New York City, the current emphasis is on forest restoration. The objective is to redress the impacts that humans have had on forested areas dating back at least three centuries. By the end of the American Revolution, in 1783, the entire forested landscape of the city had been cleared. While there has been a lot of regeneration since then, the fact that these forests are part of a city that’s home to nearly 8.5 million people (more than double the populations of Maine, New Hampshire, and Vermont combined) means there continue to be unique human-induced pressures on the forests of New York City.

Almost all of New York City’s forested natural areas see high levels of use. NYC Parks and the Natural Areas Conservancy have worked to overcome the public’s perception of the areas as unsafe because of illegal dumping and crime. “This is something that we’re working very hard to change through civic engagement, improving pedestrian access, and education,” King said. The NRG has mapped over 300 miles of hiking trails in the parks, with the ultimate goal of designating and managing a formal trail system instead of the current mix of desire lines (unplanned paths created by people).

Forest Management in New York City Image

The Forest Restoration team unloading a large delivery of native trees in Alley Pond Park, Queens.

“Working on trail management has really shown me just how intensive human use can be in our natural areas – Marine Park in Brooklyn is a good illustration of this,” King said. The park is really popular for operators of off-road vehicles (which are illegal in the city), and they’ve done considerable damage to the unique maritime forest in the park. The Natural Areas Conservancy is currently working on a project, on which King is advising, to narrow and close some trails through ecological restoration. They also hope that by increasing positive park use they’ll reduce illegal ATV access. “Our efforts in Marine Park include planting 7,000 trees and shrubs and engaging hundreds of local volunteers to create more than five miles of well-marked hiking trails,” explained Sarah Charlop-Powers, the executive director of the NAC.

There are similar efforts underway in other forested natural areas within the city. Alley Pond Park in northeastern Queens illustrates both the indignities once suffered by natural areas in general and the promise of restoration. Until the 1970s, the wetlands and forests of this 635-acre tract were treated as dumping grounds both by city residents and by contractors working on the Cross Island Parkway in the 1930s and the Long Island Expressway in the 1950s.

Restoration of Alley Pond Park by a variety of collaborators began in earnest in 1987. To date, 100 acres of the park have been restored, an effort that included planting 58,000 native trees and shrubs with the help of volunteers. Currently, NYC Parks is focusing on the final phase of work in a 30-acre parcel on the east side of Alley Creek, where a coastal forest desperately needed intervention. “The entire area was dominated by nonnative invasive plant species, including woody vines like porcelain berry and bittersweet that strangle and kill mature trees,” King said. After removing hundreds of tires and other debris, the NRG applied strategic herbicide treatments to remove invasive plants, then planted native trees, shrubs, and herbs and provided supplemental irrigation and other forms of intensive management during the natives’ establishment period. Now, hikers in this section of Alley Pond Park can follow distinct trails amidst wildflowers and newly established native trees like maple, birch, hickory, oak, hackberry, sweetgum, and tulip poplar.

The NRG’s forest restoration process seeks to mimic natural succession by establishing vertical layers of native species. Some of the native trees, shrubs, and herbaceous plants are chosen for their ability to establish rapidly, because closing canopy cover is essential. “Much of our canopy is still broken from Hurricane Sandy and other recent severe storms, and in urban areas, canopy gaps are not a good thing – they facilitate the spread of our sun-loving invasive species and basically just give us more and more work to do,” King said.

Forest Management in New York City Image

A look at an urban forest (Hunter Island in the Bronx) that has been degraded and is in need of restoration.

The NRG’s approach to the restoration of natural areas involves several innovative techniques. They ensure that each layer of plant material performs a vital function, while anticipating the future cultural needs of the site as conditions change. For instance, there are some versatile shrubs – such as elderberry, grey dogwood, and nannyberry viburnum – that tolerate full sun but also do well in at least partial shade. As such, those shrubs can serve as a nurse crop to young trees.

Additionally, a strategy of planting a broad diversity of species offers the forests greater protection against the threat of exotic insects, which can devastate a monoculture. There’s a special emphasis on choosing plants that have mutually reinforcing, highly adaptive seed dispersal – for instance, the silky dogwood shrub, which fruits in late summer, attracting migrating songbirds that also consume the blue fruits of the tupelo tree that are out at that time.

King feels that it’s important to focus on projects in large areas with “core” forest (forest parcels that are as far as possible from the forest’s boundary). Projects are prioritized based on ecological landscape connectivity and prior investment. And she doesn’t want anything that has already been restored to revert back to being fully invaded by invasives, so restored areas are swept annually for the first two years to remove non-native species, and subsequently at 18-month intervals until the newly planted tree canopy closes (which can take decades).

The sheer scale of the project means that it will continue for decades, but King says that she has a clear vision of a time when “all forested areas are dominated by native species and that invasive species have been managed to the point that natural forest regeneration is occurring.”

 
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