As cities grow and the struggle to address climate change and its effects continues to mount, the importance of the urban tree has also grown. Efforts to cultivate urban tree canopies abound and are popular with policymakers and the public alike. Trees provide much-needed shade, remove air pollution, absorb carbon, and even increase property values. But boosting the urban treescape has one element that often gets overlooked: It’s one thing to plant a lot of trees—but it’s something else to maintain them.

Technology has long played a role in efforts to track, map, and quantify the big-picture impacts of urban treescapes, from the environmental to the economic, a topic covered in this column in 2018. But new technologies have emerged and evolved since then, and some of the most intriguing are focused not just on high-level policy impacts but on the crucial issue of long-term maintenance. One specific example: adequate and timely watering, especially for younger trees, must be part of planning if the urban tree population is to endure.

Increasingly, cities are leveraging sophisticated tree-data tools to encourage and enable citizen engagement with urban tree maintenance, and in some cases even directly involve citizens in caring for the canopy.  

Consider a set of ongoing projects originating with CityLAB Berlin, a tech innovation nonprofit that applies data to urban problems. In recent years, Berlin, one of the more tree-rich cities in Europe, lost 20 percent of its trees thanks to high temperatures and a dearth of rain. That’s partly because monitoring and maintaining individual trees can be a complicated and heavy burden for municipal governments. So in 2020, CityLAB launched Gieß den Kiez (Water the Neighborhood), a digital platform that made government tree data available and accessible to the public. This made it possible for citizens to learn about local tree-watering needs—and to commit to helping out. “The application was developed based on the needs of our community,” said Yannick Müller, the organization’s head of strategic partnerships, via email.

The amount of data already available was a revelation: government projects had previously detailed and mapped hundreds of thousands of trees. CityLab combined this with other data, such as rainfall figures. The result is a new digital map with data on more than half a million trees, indicating watering levels and dates, cross-matched with watering needs based on age and species. Feedback and insights from a highly tree-engaged chunk of the citizenry helped shape the platform’s subsequent development. Some individuals had already essentially adopted, and independently started maintaining, particular urban trees. “They feel like it’s their own tree,” CityLab Berlin manager Julia Zimmermann told an interviewer. Citizens also had specific ideas about utilizing the city’s existing water pump system and making it more accessible. 

“A chat tool enables interaction between users, groups, and initiatives and allowed us to communicate and collect feedback,” Müller explained. Aside from resolving smaller bugs, this inspired new features, like one that displays the location and status of water pumps. It also helped support the designation of “caretakers” for specific trees, who commit to monitoring and watering on a regular basis. “This small added feature allows citizens to make use of their resources in a more targeted manner,” he said.

In 2021, the city of Leipzig adopted the tool, and a few more German municipalities have followed, according to Müller. User numbers are increasing continually, with more than 3,500 registered citizen-caretakers now watching over 7,500 adopted trees.

That said, the efforts of Gieß den Kiez remain an adjunct to public policy, not formally absorbed into official government urban tree maintenance plans. “However, the platform succeeds in raising awareness for climate adaptations in the light of future heat waves,” Müller maintains. In Berlin, for example, “it ignited a debate between different local district authorities as to what extent citizens should be involved in taking care of city trees and if that’s a good use for water.” (It is, Müller argues, considering the costs of planting new trees and the many proven environmental and health benefits of a robust urban treescape.)

One of the inspirations CityLAB Berlin has cited is the NYC Tree Map, a digital tool with roots reaching to 2016 that now maps nearly 1 million trees. “The NYC Tree Map is the most comprehensive and up-to-date living tree map in the world,” the NYC Department of Parks and Recreation declares. “Integrated directly with Parks’ forestry database, the map gives citizens the same real-time access to the urban forest that Parks foresters have on the ground.” This enables New Yorkers to “digitally interact” with the city’s tree population across the five boroughs—for instance, they can monitor a tree’s most recent inspection, with the date and inspection ID.

“Our NYC Tree Map allows casual tree lovers to easily identify trees, flag concerns, and report their care,” NYC Parks Director of Stewardship Nichole Henderson said via email. “Groups and individuals log their tree care activities into the map, like watering, litter removal, soil cultivation and mulching.” Moreover, several citizen groups monitor and use the map to coordinate more ambitious stewardship and maintenance efforts. As examples, Henderson mentions the Jackson Heights Beautification Group, an arts and environmental organization in Queens; Trees New York, a longstanding professional organization that trains “citizen pruners,” among other engagement activities; and the Gowanus Canal Conservancy, whose projects include “community science” efforts such as experiments in capturing and using rainwater. And the tree map is key to NYC Parks’ own broader Let’s Green NYC campaign, which posts “citywide street tree care activities with community partners and allows volunteers to see the visible impact, how they are directly contributing to caring for the urban forest,” Henderson said.

Similar initiatives are playing out in other major cities. The District Department of Transportation (DDOT) in Washington, DC, maintains a digital tree map that encourages citizen involvement (including reporting browning leaves or insect damage, as well as trees in need of watering). The tree map launched with a special focus on maintaining 8,200 trees planted in 2017. Elsewhere, the Adopt-A-Tree app in Athens, Greece, enables citizens to take responsibility for watering individual city trees during dry summer months. And entities like CityLAB Berlin continue to innovate: its new Quantified Trees (“QTrees”) project aims to develop a prediction system supported by artificial intelligence, drawing on databases and sensors to identify urban trees at risk from drought. A prototype is already in testing, and launch is planned for this year.

Zimmermann, of CityLab Berlin, concedes that it has been difficult to precisely demonstrate the impact of these efforts. “This is due to the nature of nature,” she said. Trees adapt slowly, so gauging the effects of watering programs could require years of monitoring growth, roots, leaves, and so on. But in the short term, the project’s data dashboard does illuminate watering patterns —and has shown that watering amounts have increased since the program started, almost certainly countering drought effects. “So the project leads at least to a better understanding and caretaking of urban green,” she continued. In some cases it has sparked local governments to support volunteers with material and guidelines for optimal watering practices.

“Trees are the new polar bears, the trending face of the environmental movement,” the historian and author Jill Lepore observed recently, in a survey of humans’ surprisingly long-lived appreciation for the arboreal. Now we have the science and technology to understand and quantify the value of trees beyond aesthetics. “If our ancestors found it wise and necessary to cut down fast forests, it is all the more needful that their descendants should plant trees,” Andrew Jackson Downing, a landscape architect, wrote in 1847. “Let every man, whose soul is not a desert, plant trees.” Fair enough. But we have the obligation—and the technology—to maintain them, too.

Rob Walker is a journalist covering design, technology, and other subjects. He is the author of The Art of Noticing. His newsletter is at robwalker.substack.com.

Lead image: Newly planted trees along a pop-up bike lane in Berlin, Germany. Credit: IGphotography via iStock/Getty Images Plus.

The impacts of climate change are being felt across the world through increased flooding, extreme heat, persistent drought, and more powerful wildfires and storms. Communities must find ways to adapt and integrate climate resilience measures into everyday decision- making. Implementing these land-based adaptations will be more effective if the strategies are linked with other objectives to create co-benefits and manage trade-offs.  

The Lincoln Institute issued a call for research proposals to expand our understanding of how land policy and land-based approaches to climate change adaptation intersect and interact with topics and issues within four of the institute’s high-level goals: low-carbon, climate-resilient communities and regions; fiscally healthy communities and regions; efficient and equitable tax systems; and functional land markets and reduced informality.  

The commissioned research papers offer findings that can inform public policy and practice across a diverse set of topics, including climate-informed zoning, land value capture, green infrastructure, and more. 

Research Papers

The Effects of Flood Buyouts and Green Infrastructure on Nearby Property Values 

Ryun Jung Lee, Wayne Day, Alexander Abuabara, Galen Newman, and Walter Peacock 

This paper identifies the effects of flood buyout activity and tree canopy coverage on nearby property values in Harris County, TX. The results point to the possibility of a reduction in the local tax base as a result of the low maintenance of flood buyout properties. 

Willingness to Pay for Climate Adaptation: International Case Studies on Private Developers’ Preparedness to Contribute to Urban Climate Adaptation 

Erwin van der Krabben, Alexander Lord, James H. Spencer, and Stephen Buckman 

This study uses a comparative case study approach of three cities – Charleston (United States), Liverpool (United Kingdom), and Rotterdam (the Netherlands) – to analyze the current and prospective role of land value capture and real estate developer contributions in inclusive urban climate adaptation strategies. 

Green Infrastructure, Home Values, Land Value Capture, and Equitable Property Assessment 

Jeffrey P. Cohen, Michael Dietz, and Yuchen Huang 

This research paper highlights the current and projected impacts of green infrastructure on housing prices in New Haven, Connecticut, and how the resulting rise in property values could be used to fund additional projects. 

Effects of Flood Hazard on Property Prices in Cape Town, South Africa 

Claus Rabe and David Karpul 

This paper investigates the impact of flood risk on residential property prices in Cape Town, South Africa, and examines flood mitigation projects proposed for two low-density suburbs. 

The Case for Climate-Informed Zoning: A Study of Fiscal Impact in Norfolk, VA  

Katherine Burgess, Michael Rodriguez, Jordan Howard, Jared Klukas, and Megan Wright 

This report examines the economic and social impact of resilience zoning in Norfolk, Virginia, which offers a cutting-edge example of climate-informed policy through the adoption of two land use plans. 

Can Removing Development Subsidies Promote Adaptation? The Coastal Barrier Resources System as a Natural Experiment  

Hannah Druckenmiller, Yanjun (Penny) Liao, Sophie Pesek, Margaret Walls, and Shan Zhang 

This study focuses on one approach to discouraging development in risky areas: eliminating implicit public incentives for development, such as infrastructure investments, disaster assistance, and subsidized federal flood insurance.  

Record-breaking heat, out-of-control wildfires, and eye-stinging smoke have made the impacts of climate change inescapable for millions of people this summer.

Heat, drought, high winds, and conditions on the ground are all making wildfires more intense, longer lasting, and more destructive, according to the National Oceanic and Atmospheric Administration, which notes that big wildfires require a number of factors to align, including temperature, humidity, and the lack of moisture in fuels such as trees, shrubs, grasses, and forest debris.

Containing the blazes is mostly a matter of land use management, says Canadian science journalist Edward Struzik, author of Firestorm: How Wildlife Will Shape Our Future and Dark Days at Noon: The Future of Fire, on this latest episode of the Land Matters podcast. The continual threat of fires also requires resilience-building techniques similar to those deployed to fend off floods and sea-level rise. “We have to learn to live with wildfire and the smoke that comes from wildfire. This isn’t going to go away,” said Struzik, a fellow at the Institute for Energy and Environmental Policy at Queen’s University in Kingston, Canada. “There’s a number of different ways that we can handle it. . . . We can do more prescribed burning where it’s appropriate. We can restore our wetlands, which would create natural buffers on the landscape. We can invest in science that provides firefighters with better tools and predicts where fire is likely to burn.”

Wildfires have become bigger, more intense, longer lasting, and more destructive for several reasons. Fires have long been nature’s way of regenerating forests, but Struzik blames the current situation on land management practices dating back to at least the 19th century: farmers burning and slashing their land, and mining companies doing the same, just to get at the mineral resources underground. The draining of wetlands took away potentially fire-stopping buffers. “If you think about it, a firefighter’s best friend really is a wetland, a swamp, a bog, a fen, a marsh,” Struzik said.

“Once [a fire] hits a wetland, it really doesn’t have anything to burn because things are just too wet and moist. We’ve essentially eliminated all those natural fire barriers over time and it’s bigger than an area the size of California. Fire now basically has its own way once it gets going.”

After the establishment of the Forest Service, the policy of prescribed or controlled burns attempted to mimic nature, but the practice became politically risky because many fires deliberately set veer out of control. Much of today’s wilderness has become a worst-case-scenario mix of dense, older forests, with abundant dry fuel on the forest floor due to high temperatures—all subject to the cascading effects of high winds, blazing heat, and fire-induced storms featuring dry lightning.

“Wildfire can actually create its own thunderstorm because of the amount of heat and vapor that it sucks up . . . and it rises up just like what would happen normally in a thunderstorm, and you get what they call a dirty thunderstorm that almost never produces any rain, but shoots out lightning,” Struzik said. “A great example of this was the Fort McMurray fire in the oil sands of Northern Alberta in 2016, where . . . the fires created their own thunderstorm and shot out lightning 20 miles in advance of the fire front. That’s how much energy there was, and [it] created a cluster of fires 20 miles away from the front of the fire. Firefighters at that time were thinking, ‘How do you manage this?’”

“They have their prediction scenarios or forecasting scenarios, but when you have a thunderstorm created by a wildfire, and it’s shooting out lighting 20 miles away, you’ve got a new rule book coming into play, and everybody’s adjusting to this. Also, I think that the other big thing for them is that you can no longer put people on the ground or in the air in a situation like that because it’s essentially like a small to moderate size volcano that’s blowing up. That’s how much energy there is.”

Wildfires allow forests to thin out, spread seeds, and spur regrowth that provides food and habitat for wildlife. But many of those benefits are obliviated in today’s megafires, which burn so intensely they destroy the nutrients deep in the ground, leaving behind a desert-like landscape where nothing regrows. In addition, the degraded forest loses its ability to soak up moisture and keep the soil stable, resulting in disastrous post-fire floods. Without trees to help absorb heavy rainfall, water rushes straight to rivers.

“Say a fire tears through the mountainsides in Colorado, which has happened a number of times. . . . You have all that ash, all that carbon on the ground,” Struzik said. “The thunderstorm comes in—and we are having more extreme thunderstorms for a variety of reasons and record heavy rainfalls in these spots—and it sweeps through, and then it just collects all that carbon and soot, puts it into the river, and actually threatens our drinking water supplies.

“There’s a great example of this in Waterton Lakes National Park on the Montana border. There’s a waterfall that most tourists come to see called Cameron Falls. A year after the fire following a thunderstorm, that crystal-clear mountain water that descended over the falls turned absolutely black,” he added.

The apocalyptic scenarios and feedback loops are almost certain to continue. And many of the near-term solutions lie in land.

“We’re using 20th-century strategies to deal with the 21st-century paradigm for which we’re not prepared,” Struzik said. “We’ve got to start thinking about other strategies. We’ve got to invest a lot more in science and predicting where these fires are likely to start . . . [with] a better understanding of the landscape. Where are the refugia from fires? Those areas that are unlikely to burn—or those areas that will slow or stop a fire— we should start looking at those areas from a conservation point of view, [to] protect those areas so that we don’t lose these natural barriers.”

Edward Struzik has been writing about scientific and environmental issues for more than 30 years and completed both the Atkinson Fellowship in Public Policy and the Knight Science Journalism Fellowship. His 2015 book, Future Arctic, focuses on climate change in the Canadian Arctic and its impacts on the rest of the world. He is on the board of directors for the Canadian Arctic Resources Committee, a citizens’ organization dedicated to the long-term environmental and social well-being of northern Canada and its peoples.

You can listen to the show and subscribe to Land Matters on Apple Podcasts, Google Podcasts, Spotify, Stitcher, or wherever you listen to podcasts.

For more information about climate impacts and land use and all the options for climate action and building resilience, navigate to Our Work on the Lincoln Institute website and then Low-Carbon, Climate-Resilient Communities and Regions.

Further Reading

The Second Wave: Why Floods Can Follow Wildfires, and How Communities Can Prepare (Land Lines)

‘Literally off the charts’: Canada’s Fire Season Sets Records—and Is Far from Over (Politico)

Big Heat and Big Oil (The New Yorker)

Can Mushrooms Prevent Megafires? (The Washington Post)

Ecosystem Collapse Could Occur “Surprisingly Quickly,” Study Finds (Slate)

Anthony Flint is a senior fellow at the Lincoln Institute of Land Policy, host of the Land Matters podcast, and a contributing editor of Land Lines.

Lead image: Forest fire, Penticton, BC, Canada. Credit:  cfarish via iStock/Getty Images Plus.