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On the quiet, residential stretch of Philadelphia’s Cherry Street that runs into the Schuylkill River, a series of blue and white markers bear the words “Hurricane Ida.” The first one, about a block from the water, is painted on the sidewalk: “Hurricane Ida Strandline 2021.”

Then there are blue stickers wrapped around telephone poles and streetlights in a progressively higher parade toward the river, each reading “Flood Height, Hurricane Ida, 2021.” They start at shoulder height and rise every few feet until they’re overhead, reminders of a flood that was once high enough to submerge pedestrians and cars.

These markers are part of a new interactive walking exhibit commissioned by the Academy of Natural Sciences called “How to Get to the River,” which examines the Schuylkill River watershed—its landscape, its sounds and its past and present paths through the city of Philadelphia. The exhibit is also about flooding and the ways that the city, the heart of which is nestled between the Schuylkill and the Delaware Rivers, must think about how to adapt to increasingly powerful storms like Ida.

It has been almost a year since Ida swept through the Northeastern U.S. and Philadelphia, bringing torrents of rain, destructive tornadoes and high-speed winds. In Pennsylvania, Ida’s remnants caused millions of dollars in property damage, swamped the Vine Street expressway, overwhelmed water plants, destroyed homes, and killed four people. More than 83,000 households in Pennsylvania applied for FEMA assistance in the aftermath of the hurricane.

Global warming makes hurricanes more intense. Scientists say that storms like Ida, once atypical, will become the new “norm,” and Ida is just one example of the extreme weather that cities now face. Depending on where you are, the present–and the future–looks like blazing heat waves, devastating wildfires and regular flooding, or some combination of the three.

“That’s what we should have learned from a year ago, that the urgency is now,” says Jerome Shabazz, executive director of the Overbrook Environmental Education Center, of Hurricane Ida and its aftermath. For cities like Philadelphia, in the U.S. and around the world, adapting to the new norms of climate change is more pressing than ever before.

Climate adaptation is one of the main themes of COP27, the annual U.N. climate conference, which will take place this year in November in Egypt. The conference’s mission statement recognizes that extreme weather worsened by climate change has become “an everyday reality of our lives.” At COP26 in Glasgow last fall, progress was made toward financial support for climate adaptation in developing countries, and a work program on the Paris Agreement’s Global Goal on Adaptation was launched to better understand the goal and how to reach it.

In July, at the Sydney Energy Forum, Mahmoud Mohieldin, the U.N. climate change high-level champion for Egypt, stressed the importance of focusing on adaptation, though it has been “forgotten” at U.N. climate conferences in the past in favor of an emphasis on mitigation. “We are facing severe problems when it comes to adaptation,” he says.

Philadelphia shows both the promise of cities to be leaders in adapting to a rapidly shifting climate—as well as their limitations. The questions that confront Philadelphia are echoed in other urban environments: what kind of policies, technologies and strategies will be needed to weather the rollercoaster of climate consequences in a given place, without leaving the most vulnerable residents behind? What makes any single location worth preserving or abandoning, and who gets to decide whether to stay or to go? What kind of regional, national and international aid will cities need to survive, and what will that survival look like?

In 2021, under Mayor Jim Kenney, the city released its Climate Action Playbook, which outlines the ways that Philadelphia is working to “meet the goals of the Paris Agreement,” including plans to adapt to climate change and to prepare for a “hotter, wetter future.” When former President Donald Trump exited the Paris Agreement in 2017, Philadelphia joined dozens of other American cities in publicly committing to honor the agreement’s provisions on reducing carbon emissions anyway. But reducing emissions, on its own, can’t tackle the city’s climate challenges that are already here, and getting worse. The Climate Action Playbook predicts that the city could endure 52 days of temperatures above 95 degrees Fahrenheit by 2100, and that this heat will be concentrated in some neighborhoods more than others. More rain, snow, and storms will cause increased flooding and water damage throughout the city.

For Mark Alan Hughes, founding faculty director of the Kleinman Center for Energy Policy at the University of Pennsylvania, cities can—and must—become a major part of the solution to climate change. The author of an audiobook called Livable Cities, Hughes sees cities as “powerful tools for collective action,” both now and in the past. “Cities can be the places where the maximum number of people can overcome the maximum number of challenges,” he says. On climate adaptation, Philadelphia still has a long way to go (the city “continues to be vulnerable on almost everything” when it comes to climate, he says), but it is “well-positioned to get better.” Hughes cited the Philadelphia Energy Authority’s Solarize Philly initiative as an example of what the city can do well when it comes to climate policy, taking on the thorny logistics that are necessary to actually implement a program like solar panel installation.

One adaptation to increased rainfall is Green Stormwater Infrastructure (GSI) systems, which are highlighted in the Climate Action Playbook. In Philly, Shabazz was a pioneer when it comes to GSIs, which work by slowing and capturing runoff using stormwater and green roofs, gardens, planters and other design innovations. “What we did was create a demonstration site,” he says. “And what it has done ultimately is encourage more tree planting in the area and more planned use of stormwater management.” Launched in 2011, Philadelphia’s Green City, Clean Waters program is using green infrastructure to reduce the volume of water entering the older part of the sewer system.

When it comes to dealing with excessive heat, efficiency is a key consideration, according to Simi Hoque, an associate professor at Drexel University whose research centers on energy conservation and sustainability as well as climate resilience. “Something as easy and as cost-effective as putting shading on windows is going to have a far more adaptive effect than putting a green roof on a building,” she says.

The effects of heat islands mean that some neighborhoods in Philadelphia can be as much as 22 degrees hotter than others, so Hoque is also focused on ensuring that adaptive solutions are mindful of the historical disparities that continue to exist in the city. Hoque sees Philadelphia’s public health emphasis as one positive sign that the city is keeping equity and environmental justice front and center as it moves to combat climate change.

Shabazz says he is heartened by increasing collaboration between health departments, environmental agencies, and neighborhood groups on the problems of climate adaptation and climate-related health issues, but he feels that more could be done to build community trust. “There is still too big a gap between the actors who are influencing policy and the people who are affected the most,” he says.

According to Hughes, perhaps cities’ greatest adaptation blindspot is the failure to consider the difference between place-oriented and people-oriented solutions: “Do you want to invest in people or do you want to invest in places?” Until we take a hard look at that question and its implications, he says, “we’re not really having a fully coherent conversation around cities adapting to climate change.”

Sometimes those goals overlap; cities’ population density makes them ideal for things like cooling stations, for example, because they can serve larger numbers of people than they would in rural areas. But the goals of saving people and of saving a specific place don’t always align. “It’s a hard decision to stay attached, and it’s obviously a hard decision to give up that attachment,” Hughes says. “Do you want to make a wet place dry? Or do you want to move to a dry place?”

For all of Philadelphia’s progress and lofty plans, experts caution that the city will never be able to handle climate change and its attendant consequences on its own. “Being in the vanguard is good, but it’s never going to be enough,” Hughes says. “This challenge is hugely expensive.”

Hoque echoed this sentiment. “The city is struggling with finding the resources to do the things that they have promised that they’re going to do,” she says.

This is why global events like COP27 are so important, because climate change adaptation cannot and will not be solved by any one city, state, or country acting alone, and there is still so much to be done. “As a threat, this is existential,” Hoque says, and, despite the city’s work on climate over the past 15 years, “we’re not acting as though it’s existential.”

“How to Get to the River,” which was developed in partnership with the local theater company New Paradise Laboratories, was partly inspired by Toni Morrison’s essay “The Site of Memory.” “All water has a perfect memory,” Morrison wrote, “and is forever trying to get back to where it was.” The exhibit includes maps of the streams that used to crisscross the land that Philadelphia now occupies, and it also shows visitors how those waterways are buried now, swallowed up by the sewer system. A colorful sidewalk mural illuminates the historical path of Minnow Run, one of those disappeared creeks. “I think of these creeks often,” reads the text at one stop on the walk, “when my feet hit the ground, when my friend and I hear the sound of rushing water through the manhole cover, when it rains.”

If you toggle between old maps of Philadelphia and the present-day grid, you can watch the Schuylkill’s boundaries swell and contract. In the early 19th century, the river was tamed using dams, river pools, and canals in order to make the route navigable for industry. In her essay, Morrison takes a long view of floods and what they mean. “‘Floods’ is the word they use,” she wrote. “But in fact it is not flooding; it is remembering. Remembering where it used to be.”

Like Morrison, “How to Get to the River” invites participants to experience watersheds as living things, with a will of their own. At the final stop, you can sit in a wooden structure built at the river’s edge and listen to the music of the water, live audio of the river in front of you interposed with underwater recordings. The current burbles and chirps, and if you lie back against the resonant benches, you can feel the river’s liquid pulse in your ribcage, a second heartbeat.

Maybe it is possible to see adaptation as something other than a desperate race to preserve what are ultimately arbitrary borders and artificial ways of being. Perhaps adaptation can also be about return, about moving forward with the history of the land and water as a guide, seeking to respect the natural world rather than to subjugate it. “The act of imagination,” Morrison wrote, “is bound up with memory.” Sometimes imagining a different future requires looking back at the past.