Main photo: Aerial view across Christchurch city.
Christchurch has lost 14.5% of its urban tree cover; now a UC AI tool shows exactly where, helping cities act faster on climate and planning.
A new artificial intelligence (AI) tool developed by researchers at Te Whare Wānanga o Waitaha | University of Canterbury (UC) is revealing where trees are being lost across Christchurch, including individual residential properties, which is opening the door to healthier, safer and cooler neighborhoods.
The study, led by UC PhD candidate David Pedley, a recipient of the Geospatial Research Institute (GRI) PhD Scholarship, and Professor Justin Morgenroth from UC's School of Forestry, uses a combination of aerial imagery, LiDAR data and deep learning to detect and measure changes in urban tree canopy over time. The research, Detecting and measuring fine-scale urban tree canopy loss with deep learning and remote sensing, was published in the ISPRS Open Journal of Photogrammetry and Remote Sensing.
"Urban trees play a critical role in making cities more liveable," Pedley says.
"They help cool neighbourhoods, improve air quality and support wellbeing, but until now, it's been difficult to track exactly where and why we're losing them."
Focusing on Christchurch, the research mapped tree canopy loss between 2016 and 2021 with a level of detail not previously possible. The results show that approximately 14.5 percent of the city's urban tree canopy was lost over that period, with the majority occurring on residential land.
"What's new here is the level of precision we can achieve with the data. We can now identify tree loss at the scale of individual properties, which creates opportunities to better understand the drivers behind it and respond more effectively."
Professor Morgenroth says the ability to pinpoint where canopy loss is occurring could support more targeted decision-making by councils, planners and communities.
"If we want to maintain the benefits of urban trees, we need good data to inform our decisions. This kind of insight can help guide planning, policy and investment to protect and grow urban forests where they are needed most," he says.
Urban trees are increasingly recognised as critical infrastructure in cities, helping to reduce urban heat, manage stormwater and support biodiversity, as well as contributing to the local population's mental health and overall quality of life.
The researchers say their approach could be applied in cities around the world, using publicly available data to better understand urban tree dynamics and support more sustainable urban development.
"This isn't just about measuring loss-it's about giving cities the tools to make better decisions for the future," Pedley says.
