There have been numerous debates that call attention to the energy and time organizations spend managing invasive species populations and the long-term value of that investment. The New York State Department of Conservation defines invasive species as those with the ability to thrive and spread aggressively outside their natural range and cause economic or environmental harm to the surrounding ecosystem.
In a world that continues to globalize, eradicating most invasive species seems nearly impossible and, some would say, futile. For many years, conservation professionals have been trained to associate invasive species with environmental destruction. Or as Peter del Tredici, a senior research scientist at the Arnold Arboretum of Harvard University, eloquently writes in his book Wild Urban Plants of the Northeast, “calling a plant invasive allows us to blame it for ruining the environment when really it is humans who are actually to blame.”
A growing number of scientists are encouraging conservationists to embrace some of these species in the face of dwindling resources and a rapidly changing world. Many scientists argue that the benefits of these species outweigh their destructive nature and admit that loss of biodiversity is an unfortunate reality. While these complicated issues are worthy of debate, managing invasive species in Central Park is a necessity. As stewards of Central Park, the Central Park Conservancy finds it important to control invasive plants that compete with native and non-native plants we have chosen to grow in our landscapes. Without management of these species, the Park would function very differently and provide a much different visitor experience.
Take Japanese knotweed (Polygonum cuspidatum) for example: a plant Conservancy staff have been dealing with for decades. You couldn’t ask for a more urban-tolerant plant – it needs no care in order to grow – and it contributes to erosion control, which is one of the reasons it was brought to the United States. It provides wildlife habitat (186 insect species feed on it), and Japanese knotweed honey can be bought in the region. It has many attributes and can serve many functions needed in our urban landscape – but at what cost? Its aggressive and rampant growth has led to houses in England with Japanese knotweed-ridden yards to be deemed unsaleable. It can push up through pavement, and its perseverance makes its eradication nearly impossible. The destructive nature of this plant on the Park has been noted for years. In 1927, Herman Merkel, a landscape architect hired by the New York City Department of Parks & Recreation, noted of Central Park’s North Woods, “Polygonum [knotweed] has been allowed to crowd out other more desirable plants, and in some locations has been permitted to spread at will.” Japanese knotweed stands can become dense and obscure views, and the plant holds trash between its stems very well.
The good news, however, is that the Conservancy’s aggressive management of this species over time has allowed for more functional plant diversity in beautiful, safer, and cleaner landscapes all over the Park. Next week, we’ll highlight invasive species management efforts in the Hallett Nature Sanctuary that have resulted in notable plant species diversity.