Taking on Invasive Species

Harmful plants or animals that are not native to an ecosystem are considered invasive species, and without natural predators—or even purpose—within an ecosystem, they spread aggressively and can take over a habitat. Invasive species damage the environment, and the nation spends billions of dollars annually to keep them out of forests, farms, gardens, marshlands, and bays. Over four years, a faculty-student team led by Rutgers’ School of Environmental and Biological Sciences ecologists Joan Ehrenfeld and Rebecca Jordan partnered with volunteer citizen scientists to canvass a large swath of forest that is under attack. The New York/New Jersey Trail Conference and Rutgers Invasive Plant Monitoring Project helped researchers chart the location and extent of the invasion, data that can be used in stemming the growth of habitat-snatching plants run amok.

How Do the Invaders Get Here?

Invasive species can enter a region under the most innocent circumstances. With nurseries touting their beauty, hardiness, and need for little water, many invasive species are routinely purchased and planted by home gardeners. Some are sold as deterrents to foraging deer, while others were brought to the United States more than a century ago for research and ornamentation or as gifts. Still others enter by accident, such as weed seed mixed into crop seed, or species that attach to the bottom of an ocean liner. No matter their route to taking root, the invasive species are here, hundreds in New Jersey alone. And each year they cause more damage. View the photo gallery below to learn more about how invasive species disrupt ecosystems and how Rutgers researchers are gaining a better understanding of the problem.

  • Highlands overview.
    Into the Woods with a Purpose

    "Invasive exotic plants are a threat to forest health and biodiversity," says Joan Ehrenfeld. This project assessed invasive species across thousands of acres in the Highlands region. Researchers, including student Kai Li Tan, above, surveyed 175 miles of hiking trails from New Jersey's Ramapo Mountains to New York's Harriman State Park. The work was funded by the U.S. Department of Agriculture.

  • Getting ready at Wawayanda.
    Into the Woods with a Purpose

    Because there are not enough trained scientists to go around, ecologist Joan Ehrenfeld, center, and her team trained "citizen scientists"—avid recreational hikers—to identify native and invasive species. Joining Ehrenfeld at New Jersey's Wawayanda State Park, graduate student Kristen Ross, left, and undergraduate Alexandre Chausson get ready to retrace the volunteers' steps.

  • Trail guide.
    Into the Woods with a Purpose

    More than 130 volunteers in teams of two sampled two-mile sections of hiking trails. Later, "validators" like Ross and Chausson—highly trained in plant identification—collected data along the same stretches of trail to assess the volunteers' accuracy.

  • Joe Steinfeld identifies bittersweet.
    Into the Woods with a Purpose

    Undergraduate Joe Steinfeld checks the identification of Celastrus orbiculatus, or oriental bittersweet, a very common and dangerously invasive vine.

  • Bittersweet overwhelms a tree.
    Into the Woods with a Purpose

    Bittersweet's thick climbing vines can strangle a tree, its prodigious leaves can block the sunlight from reaching a tree's leaves and prevent photosynthesis, and its growth into treetops can weigh a tree down, making the tree much more likely to topple over in wind and ice storms.

  • Bittersweet leaves and berries.
    Into the Woods with a Purpose

    While U.S. nurseries generally do not sell Celastrus orbiculatus (opting instead for its safe American cousin, Celastrus scandens), it's easy to find non-U.S. sellers touting the vine, like this from the United Kingdom: "A wiry stemmed climber grown mainly for its colourful fruits, which split open in autumn to reveal bright red seeds. Golden autumn foliage. Height to 30 ft. Best up a tree."

  • Ehrenfeld is an expert in ecosystems ecology.
    Into the Woods with a Purpose

    Ehrenfeld, right, an expert in wetland ecology, ecosystems ecology, and urban ecology, teaches undergraduate and graduate ecology courses and serves on several federal and state advisory committees involving water management, wetlands, and invasive species. In April she will present a public talk about the Highlands project at the University of Wisconsin.

  • Barberry on forest floor.
    Into the Woods with a Purpose

    By altering soil chemistry, Japanese barberry (Berberis thunbergii), seen here near the forest floor, reduces the depth of essential litter layers in forests. The litter layer is where bacteria, fungi, worms, insects, and other decomposers eat dead plant matter and create new nutrient-rich soil that plants need to thrive.

  • Barberry close-up.
    Into the Woods with a Purpose

    A thorny shrub with bright red berries, Japanese barberry is promoted as an excellent deer repellent and is routinely sold by American nurseries that suggest using it to border a property or garden.

  • Kristen Ross.
    Into the Woods with a Purpose

    Ross, above, now employed at the Rutgers/Brooklyn Botanic Garden Center for Urban Restoration Ecology, earned her Ph.D. in 2008, working with Ehrenfeld. In August 2009, Ross, Ehrenfeld, Rebecca Jordan, and colleagues presented the Highlands study results at the Ecological Society of America's 94th Annual Meeting in New Mexico. Ehrenfeld hopes to publish the study results later this year.

  • On the trail.
    Into the Woods with a Purpose

    "Finding where invasive exotic plants occur in large forested areas is not easy," says Ehrenfeld. "By training volunteer hikers to identify a dozen of the most important noxious species and to collect real data, we were able to survey over 175 miles of hiking trails in northern New Jersey and adjacent New York and gain a large amount of data that can be used to help manage this problem."

  • Joan Ehrenfeld, Alexandre Chausson, and Kristen Ross.
    Into the Woods with a Purpose

    The study found that volunteers were most successful in correctly noting the absence of invasive plants and in identifying commonly occurring species. After participating in the study, volunteers are more careful about what they plant in their own gardens. For them, a leisurely walk in the woods will likely never be the same.

  • Highlands overview.
    1/12
  • Getting ready at Wawayanda.
    2/12
  • Trail guide.
    3/12
  • Joe Steinfeld identifies bittersweet.
    4/12
  • Bittersweet overwhelms a tree.
    5/12
  • Bittersweet leaves and berries.
    6/12
  • Ehrenfeld is an expert in ecosystems ecology.
    7/12
  • Barberry on forest floor.
    8/12
  • Barberry close-up.
    9/12
  • Kristen Ross.
    10/12
  • On the trail.
    11/12
  • Joan Ehrenfeld, Alexandre Chausson, and Kristen Ross.
    12/12

Watch a Video

Not in My Backyard

Watch a training video prepared for the Rutgers Invasive Plant Monitoring Project to learn about three invasive tree species found commonly in New Jersey. Graduate student Wes Brooks will help you discover how to distinguish invasive trees from native look-alikes. If you find any of these invasive trees on your property, get rid of them!