Amanda Gläser-Bligh occasionally draws curious glances from passersby as she tends to the eight-year-old linden tree she has adopted outside her residence in Charlottenburg, Berlin.
“I call her Linda the linden,” she shares. “While Berliners may not be renowned for their friendliness, most people respond positively when they learn about my efforts.”
During the scorching summer months, Gläser-Bligh transports around 20 liters of water to Linda once a week. Although it requires several trips up and down stairs with a watering can, she has observed that the tree no longer droops under the summer sun. Linden trees are a defining feature of Berlin, even giving their name to the famous Unter den Linden boulevard. Their lush canopies play a crucial role in cooling the streets, and their flowers provide essential nectar for local bee populations.
Gläser-Bligh became involved with the tree through the Gieß den Kiez initiative by CityLAB Berlin, which translates to “water your neighborhood.” This project employs an interactive map that monitors over 900,000 trees in Berlin, estimating their water requirements based on factors like age, species, and local rainfall patterns. This real-time data distinguishes Gieß den Kiez from other tree mapping efforts globally, enabling volunteers to coordinate their activities across the city.
Users can view the last time a tree was watered, log their own watering efforts, and see color-coded indicators for trees in urgent need of hydration. For example, younger saplings, lacking the robust root systems of older trees, require more frequent watering to thrive. Gieß den Kiez also provides guidance on effective watering techniques, rainwater collection, and the locations of water pumps throughout Berlin.
“It feels quite engaging, almost like playing a video game,” Gläser-Bligh remarks. “Many people might want to help water trees but may hesitate due to uncertainty about whether it’s their responsibility. However, with this app encouraging participation, it becomes clear that it’s the right thing to do.”
Since its inception in 2020, the Gieß den Kiez project has attracted 12,000 registered volunteers who utilize the platform. Their contributions are a valuable complement to the efforts of local street and green space authorities, which are already responsible for watering thousands of trees but often struggle to keep pace during the increasingly hot summers in Berlin.
“I was genuinely surprised by how passionately people care about trees; for many, it’s akin to caring for a pet,” states Anna Mehrländer, who has been overseeing the Gieß den Kiez project for over a year.
“Climate change is becoming evident in our surroundings. However, watering a tree is a small act that helps communities adapt to hotter summers. It also fosters a sense of community at a time when many are working from home and glued to their screens.”
Notably, the highest annual spike in tree waterings occurred shortly after the platform’s launch in 2020, coinciding with the onset of the COVID-19 pandemic, when nearly half a million liters were used. Anna suggests that this surge was driven by people’s desire to reconnect with nature and their communities. Watering activities tend to increase during heatwaves; for instance, on June 27, when Berlin set a record high of 39.9°C (103.8°F), residents collectively poured 8,000 liters onto trees citywide.
Research increasingly supports the numerous advantages of urban trees in combating climate change. Studies indicate that trees help cool the air, alleviate urban heat islands during heatwaves, and mitigate flooding risks during heavy rains. Additionally, they enhance biodiversity, reduce air pollution, and can positively influence mental well-being.
Urban forestry expert Dr. Cecil Konijnendijk advocates a 3:30:300 guideline for urban greening: every resident should be able to see at least three trees from their home, live in an area with 30% tree canopy coverage, and be no more than 300 meters from a park or green space.
“Historically, trees were viewed primarily as aesthetic elements in urban settings,” Cecil notes. “However, we are beginning to recognize them as vital infrastructure.”
He endorses community initiatives like Gieß den Kiez that enhance municipal efforts in tree care. Beyond watering, Konijnendijk emphasizes the significance of soil volume and underground space to promote healthy root development in trees.
“I always ask, ‘How do you take care of your existing trees?’” he states. “It takes 30 to 40 years for a new tree to provide the ecological benefits of a mature one. Yet, many trees are being pushed to their limits amidst increasingly hot summers, with drought becoming a significant concern.”
Cecil also believes that advancements in AI and technology could revolutionize how we monitor and maintain the health of urban trees. He points to the growing use of soil sensors and city-wide lidar scanning of tree canopies, with cities like Malmo and Singapore leading the way in innovative urban forestry practices.
The open-source nature of Gieß den Kiez allows other cities worldwide to adopt the map. Residents in Potsdam, Leipzig, Magdeburg, and the 17th arrondissement of Paris have already initiated their versions of the platform to facilitate tree watering.
“Anyone can replicate the code and establish their own Gieß den Kiez,” Anna explains. “The only requirement is a dataset of all the trees in your city. This can be implemented anywhere, from China to the UK.”
Back in Charlottenburg, Gläser-Bligh recently noticed another individual using the map to water a tree across her local park, a promising indication that the Gieß den Kiez initiative is gaining traction.
“It’s a small step, just a very small step,” she concludes. “But it has a direct impact on the climate.”
