Living on the Edge in New York City

This year’s Climate and Society class is out in the field (or lab or office) completing a summer internship or thesis. They’ll be documenting their experiences one blog post at a time. Read on to see what they’re up to.

David Ng, C+S ’18

A young, unhealthy spruce tree hidden in the undergrowth.

When I started my internship, I hadn’t imagined I would be wading through thickets of chest-high grass and battling prickly plants and biting insects on my field trips to the Bronx. But while it’s been a little more “jungle” in the “urban jungle” than I was expecting, that’s been a pleasant surprise.

Enjoying a quiet lunch break while sitting on a cool, soft mat of leaf duff was not on my to-do list, but I was grateful for the opportunity on one of these trips. The thick canopy of mature trees provided welcome shade on a sweltering June afternoon. I really have to hand it to New York City’s Department of Parks for planting this oasis between an industrial facility and a bridge abutment. It is nice to see that there are still places in our densely packed city where nature is allowed to take its course.  

Since 2005, New York has planted 7,000 trees as part of the urban reforestation effort called Greening the Bronx. The trees are intended to provide vital ecosystem services to the city, such as mitigating the urban heat island effect (where urban areas have been documented to be measurably warmer than nearby rural areas). My team at NASA’s Goddard Institute for Space Studies has the privilege of seeing the fruits of these efforts. We have been tasked with characterizing the extent to which these trees may mitigate the heat island effect in the Bronx. The trees in our study are on streets, along roadways and college campuses as well as in public housing greenspaces and city parks. Given the fractured nature of greenspaces in the city, these trees are all living in edge communities or creating an edge community unto themselves within their solitary tree pits, the small squares of soil carved out along sidewalks. Edge effects occur at the boundaries of two habitats, in this case the urban, impervious pavement and thel soil of the tree pit.

Separated from their natural environment and from each other, city trees experience high mortality rates. Sadly, our team has seen this for ourselves. At first, we hadn’t noticed the high mortality of the trees because many tree pits had apparently been paved over. We couldn’t determine whether our maps had failed us or the trees had simply died. But after coming across a number of leafless trees and tree stumps, we began to understand the challenge city life presents to these humble residents.

While our team is primarily concerned with the potential for trees to reduce air temperatures in the city and reduce energy loads in the summertime, we’ve been focused more on simply the challenge of finding specific trees in forests full of trees. So when we came upon a Parks Department team with a backpack GPS unit taking a tree census, I thought this could be the start of that proverbial beautiful friendship.

But the team informed us that the information they were collecting would be for Parks Department use only. Another missed opportunity to connect! I couldn’t help but draw a parallel between how the trees were living in fragmented communities and how our study teams were working in fragmented scientific communities. How much more fruitful might the trees be if they could be living together in expansive, interconnected tracts? How much more fruitful might our studies be if we could combine efforts and information?   

Swans take in the scenery on a sunny summer day in the park.

Parting ways, we continued trudging on toward our objective. That is where we encountered undergrowth as tall as the trees we were studying. It was gratifying to see that, even in our packed-to-the-gills city, there were still places that could remain relatively undisturbed long enough for a little wildlife to reassert itself.

After bushwhacking our way through this brush to take measurements of the trees we were able to identify as sours, we took cover under a mature stand of trees. The sun had done its job and now the trees were doing theirs. The breeze felt cooler here, and I appreciated it more, too. I was pleasantly surprised by how cool the leaf litter was despite the oppressive heat. Small victories. The little things in life really do make it. And the swans at the shore made a convincing closing argument.