In Melbourne every tree in the city is tagged and given an email address, while in Milan residents can read about their local trees online
Trees are either life savers or dangerous, good to hug or to kick, and they need protecting or cutting down - it all depends on who you ask.
Cities are increasingly turning to trees and green spaces as protection from heatwaves, flooding and air pollution. Selling the idea to their citizens is easier in some cities than others though, urban officials said at the first World Forum on Urban Forests.
Melbourne, which plans to nearly double its canopy cover by 2040, has tagged every tree in the city, and given each one an email address, triggering messages like: "Dear 1037148, you deserve to be known by more than a number. I love you. Always and forever."
One of Toronto's most popular regulations forbids people from cutting down mature trees even in their own gardens, said its former mayor David Miller, now North America director of the C40 network of cities.
But some people fear trees will fall over in a high wind causing damage or worse, or create insect infestations in their homes, Italian city officials said at the meeting this week.
In parts of Munich, the need for more housing or fewer traffic jams far outweighs any thoughts about planting trees among residents, said Anna Steidle landscape architect and resident of Munich.
"Trees are a danger, in the opinion of my neighbours," she said. "No (city officials) talked to them about urban forests, nobody talked to them about trees," she said.
It is important to make residents aware of the benefits trees offer - which far outweigh the negatives - officials said, adding that cities need to plant trees that are resistant to strong winds, drought, or flooding depending on the location.
Milan residents can read about their local trees online, and see what each one provides, like better drainage, storing carbon and improving air quality.
Trees and parks not only protect cities from the impacts of climate change. They can also go some way to preventing disease and boosting people's mental health, say people in the sector.
In Britain, a group from Mersey Forest are developing nature-based therapies that they hope could even be prescribed by doctors instead of medicines.
The group organises walks in nature, group gardening, conservation projects, and mindfulness in nature. They are studying the benefits these have on local populations, especially in deprived areas.
"There's really strong evidence that we in the environment sector can ... help people live healthier and longer, and recover from illness more quickly," said Claire Olver, project development officer at The Mersey Forest.
Trees help reduce asthma levels, stress, rates of cardiac disease and strokes, and they lower obesity levels by encouraging exercise, said Vittoria Zanuso, senior manager at the New York-based 100 Resilient Cities network.
"If cities don't expand their forest cover, it will be a tragedy," she said in an interview.
"They will experience worsening air pollution, worsening urban flooding, even loss of sense of community," Zanuso said.
Trees are needed most in the poorest areas, which are already suffering from higher obesity, pollution and stress, she said, adding that "city leaders tend to beautify areas that need it the least".
Any views expressed in this article are those of the author and not of Thomson Reuters Foundation.