Trees are a powerful solution to the climate crisis. They reduce the risk of landslides and floods, improve air quality, and even protect mental health.
In this era of “global boiling,” trees offer critical cooling and shade. They are estimated to reduce surface temperatures by up to 12 degrees Celsius—a temperature difference that can quite literally save lives on a hot day. In the United States alone, urban forests remove an annual 711,000 metric tons of air pollution. Further, planting more trees could remove another 535 million tons of carbon pollution annually, offseting the pollution from 116 million cars.
Around the world, cities are turning to tree planting initiatives to improve biodiversity, beautify public spaces, and provide critical passive cooling to better protect people from extreme heat. Our Chief Heat Officers are leading the charge and have planted over one million trees across their seven cities.
From planning to planting, nature-based solutions require long-term, strategic consideration. Across four of our partner cities, our Chief Heat Officers have clearly shown how they’re approaching these challenges to ensure these investments in nature can survive and thrive, protecting people for generations to come.
1. Planning before planting in Athens, Greece
Instead of considering heat as an afterthought, the Heat Risk Reduction Guidelines make sustainable, cooling urban design a clear priority. The city of Athens developed the resource to inform city planners of the best greenery, water features, and heat-reducing materials for future construction and retrofits. The guidance includes clear targets for green cover as well as options for green structures like balconies and roofs. They also share insights on how to select the right species of tree to account for water needs, pest management, and space demands.
“Cities must plan how they plant trees,” explains Global Chief Heat Officer Eleni Myrivili. “Frameworks like Athens’ Heat Risk Reduction Guidelines can ensure that cities are using their resources most effectively and building the tree canopy in the right way.”
By planning before planting, cities can improve survival rates. One of the clear challenges of urban greening initiatives is working in environments not designed for nature. Without proper planning, urban greening initiatives can fail. Most trees should live over 50 years; but the United States Department of Agriculture found that trees in urban areas lived an average of 19 to 28 years.
Urban trees must withstand pollution, poor soil quality, insects, disease, and limited space. A strategic planting plan can ensure that cities do not waste valuable resources and can preserve trees for decades to come.
2. The fruits of community inclusion in Dhaka, Bangladesh
Across Dhaka North, informal settlements can face blistering temperatures. Looking for affordable and impactful solutions, the city’s first Chief Heat Officer Bushra Afreen turned to nature-based solutions. By increasing the tree cover across the city and within informal settlements, Afreen planned to reduce temperatures and provide shade at the hottest parts of the day—a simple solution that can mean the difference between heat illness and lifesaving cooling.
The initial strategy focused on shade alone. Afreen and her team selected species that would help rapidly expand shade cover while surviving in the urban environment. However, once she began meeting directly with the women who live in the heat-exposed informal settlements, she quickly realized the plan needed to change.
“Their feedback to that was, ‘That’s not going to work. Nobody’s going to look after these trees […] if they don’t bear fruit, if they don’t bear vegetables, or if they don’t bear something that’s tangible,” she explains. “It sounds so simple, but it wouldn’t have happened without their input.”
Afreen worked directly with the community members to select new species of trees and plants to provide both food and shade cover. Already, Afreen and her team have planted more than five thousand trees across the city’s informal settlements.
3. Laying the seeds of awareness in Santiago, Chile
Extreme heat has been a growing threat, and there is a clear inequity in accessing cooling solutions. To better protect the most people, the city mapped out a planting schedule that prioritized main streets, public spaces, and schools.
Brotar is a tree planting initiative that aims to plant 30,000 low water consumption trees across the capital. The program aims to reduce surface and air temperature to protect half a million residents from extreme heat.
In the first year, the city planted 17,500 native trees. The plan prioritizes expanding the tree canopy in public spaces, including schools. In parallel to the planting, the program raises community awareness and shares the proper ways to care for trees. The educational program lead, María Jesús Riquelme, explains, “To date, we have had the opportunity to visit 40 schools in the metropolitan region, in which we have planted—together with more than 1,000 students—250 native trees and more than 1,300 plants with low water requirements […] Each planting was accompanied by an experiential and educational workshop, through which we learned how trees interact with different elements of nature.”
4. Growing resilience roots in Melbourne, Australia
Once trees are planted, the work has just begun. In Melbourne, co-Chief Heat Officers Tiffany Crawford and Krista Milne know this well. They have supported and promoted urban resilience resources, including an innovative virtual map.
The Urban Forest Visual helps Melburnians understand the status of the city’s tree canopy. With over 70,000 trees, the city is focused on maintenance—especially for its mature trees.
In addition to providing transparency, the data visualization has also served to inform future planting efforts. Many cities focus their efforts in areas of low canopy coverage; while Melbourne is also prioritizing expansion, the map allows the city to understand where trees need to be replaced. The city has plans to plant 3,000 trees annually to ensure that its canopy remains robust and cools the city.
