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Sharing Campus with Invaders

By Robyn Graygor


Upward view of juvenile redwoods, native to coastal California, along the edge of the Music Building (Photo by Robyn Graygor)

Five hundred acres of land lie beneath the soles of those who step foot on the Purchase campus. Patrick Harmon, a naturalist at the Ward Pound Ridge Reservation in Cross River, New York, finds the miles of cement pathways embellished with vegetation familiar. Harmon, a 2020 Purchase graduate, has put his environmental studies major to use working with the parks system. Now, looking back at the landscaping plants on campus, he sees an ecosystem under threat of an invasion.


Like most campuses, Purchase has been modeled by landscape architects who plant species for their beauty and low maintenance. This often means importing non–native species that are cheaper and convenient to sprinkle “the city within the country” with hints of green.


Some current non-natives on campus include willow oaks (behind the Natural Sciences Building) from southern U.S. states, wintergreen barberry (found in bushes near many buildings) from Central China, rotundiloba sweetgum (trees with rounded lobes in the Central Plaza) from southern U.S. states, Green Vase (in the Central Plaza) from Japan, Taiwan, and China, and even juvenile redwoods (along the edge of the Music Building) from Coastal California.

Rotundiloba sweetgum leaves photobomb a picture of a wintergreen barberry hedge in the Central Plaza (Photo by Robyn Graygor)

Harmon remembers the hours his class spent removing invasive callery pear trees (originally planted on campus in 1970) from the surrounding woodlands. He doesn’t think any campus should risk planting non-natives again.


“Those [non-native plants] can easily become an invasive naturalized species that can just take over an area,” Harmon explains, shaking his head with disappointment. “You know, we’ve seen it with mile-a-minute, barberry, multiflora rose, callery pears, and bradford pears. Dr. [Ryan] Taylor [associate professor of environmental studies] can attest to this because of how many we had to cut down in that woodlot.”


Harmon thinks everything from the forest floor to pollinators would benefit from replacing non-native landscaping plants with native ones. “We have a lot of native species that look nice and they’re pretty easy to grow,” Harmon says, “A lot of these pollinating species are very used to pollinating native ones, so they’re specialized. If you take away the native plants, then they lose their food source.”


Mugwort, a well know invasive plant (not planted ornamentally) fills the soil in front of the Natural Science Building (Photo by Robyn Graygor)

Harmon isn’t the only one who thinks planting non-natives will deprive pollinators.


Andrew Middlebrook works as the stewardship director at The North Salem Open Land Foundation, a land trust in North Salem, New York, dedicated to protecting open space in the area. He sees no reason to prioritize convenient plants over pollinator health. “The biggest threat is the lack of biodiversity and having so many invasive species taking over. It makes it very difficult for our native insects, pollinators and wildlife in general to adapt to that,” Middlebrook explains. “It’s like eating McDonalds every day. Yeah, you could survive on it, but are you going to be healthy? No.”


Middlebrook also stressed how Purchase’s location in Westchester County plays an essential role in the spread of invasive species. “Historically, New York City has always been a big port of entry not only for people, but trade of every type you can imagine. With that comes the introduction of non-native species, insects, seeds, you name it,” Middlebrook says. “Because of where we are geographically in Westchester County you can imagine how immediately impacted we are.”


Jocko McKean, the executive producer of the North Salem Open Land Foundation, not only encourages a focus on where Purchase is, but what Purchase is; a place which helps mold the next generation. “If we can’t convince college students at that age that we’ve caused all sorts of environmental problems, and don’t give them a means to do something about it, then I think we’ve wasted a generation,” McKean says. “Look at what history tells us already. The callery pear, the Norway maple, most people don’t even bother to think about it, and buy stuff because the nursery guy says, ‘it’s easy to clean up.’ History tells us that these things become a major problem.”


A prickly wintergreen barberry hedge pokes out into the walkway across from the Natural Sciences Building (Photo by Robyn Graygor

A study done by the EPA (United States Environmental Protection Agency) stresses McKean’s warning that a major problem may be on the way. It discussed “the ten percent rule,” which says of all non-native species planted in new ecosystems, 10% survive, and of that 10%, 10% become invasive. While this is only 1% of original species released, the EPA also reported that roughly $138 billion is spent on correcting damage done by invasive species.


Wintergreen barberry, which is found planted in hedges near the Natural Science building, is one of the species planted ornamentally at Purchase that is a part of the 1%. A report done by the District Department of the Environment of Washington D.C. described some of the characteristics which make it invasive, “It is a shade tolerant, fast-growing shrub that can alter soil chemistry.”


Both Middlebrook and McKean have dedicated their lives to fixing other people’s planting mistakes. McKean explains, “It [a focus on invasive species] is interwoven into everything we do.”


Despite these concerns, Allyson Jackson, assistant professor of environmental studies at Purchase, doesn’t see the ornamental non-natives on campus as a threat. “To me, any landscaping provides habitat for animals and that’s what I care about,” Jackson says. “Would I prefer they’re all native? Yes, but I don’t walk around being super concerned about our ornamental trees.”


She also points out the potential environmental suffering that could come from a landscaping makeover. “I think of all the labor carbon footprint of digging up and replacing things. You have to kind of balance that if it’s not a terrible invasive, all of the energy that would be put into taking it out,” Jackson says.


Jackson classifies this balancing act as a “wicked problem.”


“I just taught in my class about wicked problems in conservation. It’s like these very dire situations where there isn’t a clear, straight forward, ‘this is the thing you should do,’” Jackson explains. “Someone else is going to see you tearing up a garden bed, and be like ‘what are you doing?’ Then you have to explain ‘we’re trying to make it better.’”


A native wildflower, late purple aster, reaches out of a patch of dried grass for sunlight (Photo by Robyn Graygor)

Similarly, Ryan Taylor, associate professor of environmental studies, doesn’t find the current ornamental non-natives to be a problem. He instead predicts that the warming climate may favor these non-native species in the long run.


“I have a bias towards natives, like I would like to see what's growing here be things that were growing here in the 1700’s. But I don’t know that that's the right thing for a climate this campus will experience in 2400,” says Taylor as he scans his finger over the campus plaza on Google Earth. "If I was to go out and plant a tree now, that tree is potentially a 300-year decision. Is this the right tree for that environment?”


He feels that the ultimate goal for now is to preserve the forest's ability to function, which may require plants that favor a warmer climate. "Resilience says it can change in who the species are, provided it is still recognizable and functions as a forest.”


Taylor also revealed that while Purchase has been recognized as a sustainable and environmentally aware school, it lacks any kind of open-space management plan. “There’s not an invasive species eradication plan for the campus, and there's not an open space management plan,” Taylor says. “Since there’s not a plan to manage the campus woods, the efforts are here and there.”

Rotundiloba sweetgum pokes out from a patch of Chinese silver grass as the sun sets (Photo by Robyn Graygor)


Middlebrook strongly supports the creation of an open-space management plan. He feels any institution that is responsible for 500 acres of land should have a plan to manage it all. “A management plan for the land that they do have, and the species that they do have would be hugely important,” Middlebrook says.


An open-space management plan may not be out of the picture as a new Sustainability Coalition forms.


Angie Kim, Purchase’s sustainability coordinator, isn’t against developing a plan similar to the one Middlebrook is pushing for. “I think there’s potential to work with student researchers maybe within ENV [environmental] or other departments that have an interest in this, and get students really involved in a process like that from start to finish,” said Kim. “A forest management plan, especially as we continue to develop as an institution, I think is something that makes sense to protect such beautiful and natural land on campus.”


Yet another hope for the future of Purchase’s environment is one held by Michael Kopas, director of facilities. Kopas wants to instate a formal policy that ensures all future plantings will be native.


Redwood needles litter the ground as winter nears (Photo by Robyn Graygor)

Kopas explains, “We do not have an official mandate on campus that has been proposed and approved by shared governance or the cabinet. It is more of a conscious and intentional decision on our part to emphasize the value and desire for native plants in our campus landscape. I would like to formalize a policy. I think the timing is right.”


For Middlebrook, the timing has always been right, and time is now running out. He explains, “Why miss another generation? You guys are the next direct impact on the future. I think colleges have a serious obligation to promote ecologically sound ways of managing the land that they have.”

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