Tree canopy data for better planning

Urban green space has been declining across Aotearoa New Zealand over time.  A Parliamentary Commissioner for the Environment report found that much of this loss has occurred on private residential land. Urban trees provide benefits that are easy to appreciate but difficult to measure. They shade streets during hotter summers, improve air quality, reduce stormwater runoff, provide habitat for wildlife, and make towns and cities more attractive places to live. 

While many councils recognise the value of urban forests, few have had consistent data showing how much tree canopy they have, how it compares with other communities, or where future planting could deliver the greatest benefits.

Professor Justin Morgenroth and his team in the School of Forestry at the University of Canterbury (UC) have addressed that gap by measuring the canopy cover across 75 towns and cities throughout Aotearoa New Zealand using aerial imagery and LiDAR. For each urban area, researchers assessed 1,000 randomly distributed points to determine whether they fell on tree canopy, creating a consistent national picture of urban forest cover. Tāmaki Makaurau Auckland, Te Whanganui a Tara Wellington, and Ōtautahi Christchurch were excluded from the study because each city had previously completed detailed canopy assessments.

Cities that already hold detailed canopy assessments are using that data to support the development of their urban forest strategies. The goal of the research was to provide councils that did not have this information with reliable evidence to support planning and investment decisions. It was not designed to create a ranking of greener and less-green cities.

 Every participating council received a report detailing its baseline canopy cover and including guidance on setting canopy targets, identifying opportunities for more detailed neighbourhood assessments, and engaging communities in planting initiatives. This transforms canopy cover from an abstract environmental measure into practical information that can guide long-term planning and budgeting.

By understanding where tree cover exists and where it is lacking, councils can make more informed decisions about creating cooler streets, improving air quality, increasing biodiversity, and building resilience to climate change.

The results revealed significant variation across Aotearoa New Zealand. Tree canopy cover ranged from just 7.5% in Hāwera to nearly 59% in Waitohi Picton, with an average of 19% across the towns and cities assessed.

Justin attributes these differences to factors such as climate, population density, development patterns, and surrounding land use. Understanding those influences helps councils establish realistic goals that reflect local conditions while still delivering meaningful environmental and community benefits.