When Hurricane Ida dumped more than 3 inches of rain on Central Park in a single hour, the National Oceanic and Atmospheric Administration (NOAA) called it a “1-in-500 year rainfall event.”
The downpour broke the park’s previous rainfall record, set just 11 days earlier. It damaged scores of trees, flooded the Loeb Boathouse, transformed the area surrounding Bethesda Fountain into a massive pool and rendered much of the park inaccessible for days. It illustrated just how vulnerable the city’s parks are to the effects of climate change—and how little is understood about the relationship between parks and shifts in weather patterns.
“We have been witnessing the increasing impacts of climate change throughout Central Park for some time now,” said Michelle Mueller Gamez, manager of climate change research at Central Park Conservancy, the nonprofit that manages Central Park. Those impacts include harmful algae blooms during the summer, extreme and frequent heat waves, and intense rain over short periods of time that cause flooding, she said. “The damage that’s caused to Central Park during these extreme events makes it increasingly harder for our staff to maintain and care for all 843 acres.”
Earlier this year, the Central Park Conservancy, together with the Yale School of the Environment and Natural Areas Conservancy, launched the Central Park Climate Lab. The goal, Mueller Gamez said, is to collect data on ways in which the park is changing so its custodians can care for it accordingly. “Other urban parks are facing similar challenges,” she said. “We hope our findings can be a resource to exchange and share information with other urban landscapes.”
More than half of the world’s people now live in cities, and parks are the primary way many of them experience nature. In New York, half the population reports that their only exposure to the natural environment is through the city’s parks. They help keep residents cool (and happy); their soils absorb rainwater and runoff, and their trees improve air quality and capture carbon dioxide.
But many are in trouble. The U.S. lost more than 24 million acres—the equivalent of nine grand canyons—of natural areas, including parks, between 2001 and 2017 to land conversion. Many, including Central Park, have experienced tree die-offs due to invasive species, like the emerald ash borer, porcelain berry, lesser celandine and Japanese knotweed, which thrive in warmer weather. U.S. cities lose millions of trees each year.
“The health of the park and its forest are at risk,” said Clara Pretziger, deputy director of conservation science at the Natural Areas Conservancy. “If it’s hotter, if the lawn is flooding, if the lake itself has algal blooms, it will just be a less pleasant place to visit.”
Pretziger studies the ways urban forests soak up carbon. In a paper published this year, she found that urban forests store carbon at similar and, in some cases, higher rates compared to rural forests. “I think natural areas as a type of parkland are undervalued in their contribution to climate change mitigation and approach to adaptation,” she said.
But pests, flooding, storms, drought and high temperatures all put those trees at risk. In 2012, Superstorm Sandy, which was made more destructive due to climate change, damaged or uprooted some 800 trees in Central Park. “Some of those trees have been there for 300, 400 years. You have these large oak trees—they are really magical and they make the park beautiful—and if they topple over they’ll take a generation to [replace],” Pretziger said.
Central Park contains a multitude of microclimates—lawns, natural areas, wetlands, forests, to name a few—and caring for the entire park means understanding the different stresses affecting each area.
“We actually don’t know what the changes in rainfall and temperature [have been throughout] the park,” said Karen Seto, a professor of geography and urbanization science at the Yale School of the Environment. She said most temperature readings of the park don’t account for variability in climate conditions; a shady wooded area can be expected to be cooler than a grassy lawn.
This spring, in one of the center’s first experiments, Seto and a team of scientists took light measurements using a spectroradiometer—a tool that can help scientists assess the health of a plant—throughout the park to collect data on the park’s varied microclimates. Using satellite data, they’ll monitor changes to the park’s flora over the years.
“The goal of the project is to understand how climate change manifests itself across the entire park and to understand what are the best practices to manage the park under those conditions,” Seto said. Those practices could mean planting species that are more adaptive to flooding or warmer temperatures, or increasing the amount of spongy surfaces to soak up more rainwater, she said.
Mueller Gamez and her team are collecting data on temperature variances throughout the park by installing solar-powered sensors in the park’s lawns, forested areas, playgrounds and meadows, among other areas. She said this information will help planners think about ways to keep New Yorkers cool during increasingly frequent and intense heat waves.
“The idea is to understand the benefits of natural and forested areas and how we can enhance them if we understand we’re getting more cooling benefits,” said Mueller Gamez. Though it’s intuitive that shaded areas are naturally cooler on hot days, the sensors will quantify just how much cooler.
Pretziger said part of the lab’s mission is simply helping visitors understand how climate change relates to their daily lives. “Central Park is so iconic, and I think people really connect with it,” she said. “Learning about natural climate solutions in your own backyard can be very powerful.”