A little red fly with black spots sent everyone into a frenzy last fall. People were stomping on spotted lantern flies on the sidewalks and quick to swat at them wherever they appeared. Was the reaction merited? Or was it all due to sensationalized messaging about this invasive species? I sat down with urban ecologist and conservation biologist Amy Karpati to get to the bottom of this question and to hear her takes on the changing ecology and ecosystems in and outside of New York City, as well as the challenges and opportunities for restoring them.
Karpati is a professor at Columbia University’s School of Professional Studies where she teaches two courses, The Science of Urban Ecology and Reversing the Biodiversity Crisis, as part of the Master of Science in Sustainability Management program. Her courses focus on the study of relationships between organisms and their physical environment in an urban context, and biological conservation. She has worked with various environmental nonprofits, including the Pinelands Preservation Alliance in New Jersey and Teatown Lake Reservation, a 1,000-acre nature preserve and environmental education center in Westchester County, New York.
In the Q&A below, Karpati talks about invasive species, “green gentrification,” and how biophysical and sociocultural aspects of cities can be changed to support biodiversity and improve urban ecosystems.
The following interview has been edited for clarity and length.
What does it mean to be an ecologist? What do you study?
In the broadest term, ecologists study the relationships between living organisms and their environment and with each other. They can specialize in different sub-areas, so you can have forest ecologists, aquatic ecologists, plant ecologists, and animal ecologists. My background has been more in urban ecology and restoration ecology, so I look at cities as ecosystems and try to figure out how we can restore biological structure and function to our urban environments to make them more sustainable.
In defining ecology, you also talked about the environment. These terms are often used interchangeably. Ecosystem versus environment—what is the difference?
They’re a little different. Colloquially, they can be used interchangeably. Ecologists usually say that the ecosystem is the biotic, or living part of the landscape, plus the abiotic, or nonliving part.
The living part is the plants, animals, and microorganisms, and the nonliving part is the water, air, sunlight, and minerals. The environment is abiotic, or the nonliving backdrop that these living things are inhabiting. How all those intersect and interact is the ecosystem.
I think in common terminology, most people do include the living and nonliving part when they discuss the environment, which I think is technically accurate. I just have a separation in my head of the environment as the nonliving backdrop when I think of an urban environment consisting of infrastructure and buildings.
The spotted lantern fly became an issue last fall, but were you concerned about them? How do you assess if an invasive species is problematic?
Oh yes, I remember people were wearing spotted lanternfly Halloween costumes. Yeah, it was kind of sensationalized, but it was also a big deal, you know? Non-native species are tough because most of them have a neutral effect in the landscape. They don’t really have much of an impact, but every once in a while, you get a non-native species that becomes invasive. So it has bad impacts on the rest of our ecosystem. The spotted lantern fly is in cities. It is still a pest because it can attack street trees and park trees, but I think a lot of the concern about it was its presence outside of the city in protected forest areas.
Seeing one would send my friends into a frenzy of trying to kill the fly. Do you empathize with that?
I do. I just I find it hard to not be pessimistic about that actually controlling it. I don’t know how much of a difference that makes. People just stomping on them…I don’t think it’s going to stop the invasion, but at the very least, it raises public awareness about invasive species, which I guess has some value.
You also mentioned the forests outside of cities. How do you stop invasive species?
So, let’s start here—the urban landscape has been so dramatically altered from what it was before. Manhattan used to be a temperate deciduous forest. Clearly, you look out the window, and you don’t see that. People think mostly about plants, but we have a lot of non-native plant species that grow in the city. Some could say we have to take those out and try to bring back native species, but those native species were co-evolved with the native landscape. We don’t have that native landscape anymore, so we can’t expect those native species to be able to survive in Manhattan.
Now, some ecologists will say there’s value to these non-native species that just grow on their own out of the sidewalk cracks that are performing the same functions of carbon sequestration, stormwater control, and temperature regulation. And they’re growing here without our help because they can tolerate this kind of environment, so the control of invasive species in cities is a little more nuanced.
If you’re looking outside of the city where you do have more of the native ecosystem like a forest, the real problem is when those invasive species get into those systems and wreak havoc. In the city, they’re not really threatening a native ecosystem. It’s such a man-made mishmash landscape to begin with, but this topic of controlling species is an unsettled debate.
In your work, you talk about improving ecosystem functions and ecosystem services. What are these functions and services?
It might be easier to start by looking at the services because that’s the easiest to connect to people. Ecosystem services are the things that the ecosystem provides that we rely on for our own survival and sustainability. This includes water filtration, climate mitigation, stormwater control, pollination services for our food supply, soil fertility for agriculture, temperature control provided by vegetation, and erosion control.
So, to use soil fertility as an example: We depend on soil fertility for agriculture. The ecosystem function is the process of decomposition and the natural recycling of nutrients. The ecosystem service is the soil fertility that this decomposition provides.
What do improvements of those functions look like? What are creative solutions that can slow down or stop the deterioration of our urban ecosystem here in New York?
The funny thing here is that it seems like an oversimplification, but basically any kind of urban greening will enhance how the urban ecosystem functions and, therefore, the services that it provides for us. Planting more trees provides more cooling services. Restoring saltwater marshes around the coast of New York City provides storm surge control and carbon sequestration. Anything that enhances the biodiversity of the urban environment is going to enhance ecosystem function.
If you put a green roof on a building, it’s going to help with temperature regulation. If I plant one species, it would have low biodiversity. If we plant a bunch, now all of a sudden you’re creating a habitat for pollinators, which provides pollination services.
Do you see much difference in urban ecology issues and solutions across New York’s boroughs?
In more residential areas, there is more greenery than the more commercial business districts, but what’s cool is that there is potential for it pretty much anywhere. You often think of urban greenery as just being parks, and then we lament that there’s not enough room for parks. But you can have green walls, corridors, alleyways, and bus stops. There’s just so much potential. They’ll have different values, but they still perform a positive service.
Sometimes, communities undergo green gentrification. Have you heard of that? Green gentrification is when you think you have the best intentions of adding parks and green spaces to a neighborhood, but what can happen is that then property values go up. The original residents are priced out as property values increase, so they don’t even get to stick around for the greening of their own neighborhood because wealthier people move in.
A notorious example is the High Line. I have such mixed feelings about it; my students and I were just talking about it at the start of class today. I do like some parts of it, and yeah, it’s beautiful. I mean it was such a cool concept to take this old unused industrial infrastructure and kind of celebrate it by turning it into a public, accessible green space.
What was it before?
It was a rail line that wasn’t in use anymore, and when it was developed into The High Line that we know now, they had landscape architects and horticulturists come in and carefully design where different plants would go for the aesthetics. So it was like this abandoned area that all of a sudden we added this lush green landscape to.
If you look at photos of what it looked like before, it had plants growing all over. But they were plants that most of us would consider weeds. We like to call it spontaneous urban vegetation. So it was already performing this function because it was vegetated just naturally by the urban biota. It was performing carbon sequestration and stormwater control, and it was a green space. It just wasn’t an intentional green space, so to most of us, it didn’t have the value that an intentionally planned and manicured green space does.
Do you have thoughts on how well urban ecological issues are addressed across the boroughs?
As you would expect, the answer is inequitably. A lot of it comes down to funding and resources at the neighborhood level for how much green space can be there but also be maintained. It’s so piecemeal. You have your neighborhood-level things and city-level things, but it is without a doubt inequitable distribution of green space.
What continues to still be a challenge for you in the field and why?
It’s not so much the science; it’s the social-political aspect. If we’re talking about sustainability or conservation, we have the science and technical tools to advance a conservation sustainability agenda, but we don’t have the societal or political will to actually put those solutions in place. That’s the biggest and most frustrating challenge—the human behavioral components and missing human motivation to actually recognize that we have a climate crisis and biodiversity crisis, and it needs to be addressed now—or rather yesterday.
Where should readers interested in this space go next?
It depends on the level of understanding people have. Science journal articles are great, but so is Rambunctious Garden: Saving Nature in a Post-Wild World by Emma Marris. It challenges our perception of what nature is and tries to deconstruct that, so we can build it back up in a way that actually recognizes nature as existing in our cities and being worthy of protection or enhancements. We can create more nature in our cities, and we kind of have to at this point. It’s a good read, though a little controversial in the ecology field. It makes the argument that nature exists everywhere, not just in Yosemite or Yellowstone, but even in this abandoned rail line on the book cover.
Bhavya Jha is a second-year M.P.A. candidate at Columbia University’s School of International and Public Affairs.