Selwyn is considering a policy of “replacing one tree with at least two” after Rolleston was shown to have one of the lowest numbers of trees for a town in the country.
This comes a week after a study was released by the University of Canterbury’s School of Forestry, led by Professor Justin Morgenroth and Dr Ning Ye.
It showed Rolleston’s tree canopy cover was 7.9%, ranking it 77 out of 78 cities and towns in the study.
Other Canterbury towns didn’t fare much better, with Christchurch, the Garden City, at 13.6% (57th), Kaiapoi at 11.8% (66th), Ashburton at 11.5% (69th), and Rangiora at 9.5% (74th).
Picton was on top at 59% while Hāwera was below Rolleston at 7.5%.
Selwyn’s People, Culture, and Capability Executive Director, Steve Gibling, says the council is “looking for better direction around how we proactively manage trees, especially in a fast-paced growth district like ours”.
The said trees “play a key role in cooling through shade, providing habitat for biodiversity, and also managing storm water”.
Rolleston and its other rapidly growing urban centres have seen trees and shelter belts removed to make way for subdivisions.
Those developments have included new trees, but they take time to establish.
The council wants to improve how they plan and consider trees, both new and existing.
It was noted at a council Climate Change and Sustainability Subcommittee Meeting that there are five trees being removed for the Lincoln town centre redevelopment, but 50 trees will be planted in their place, with special strata vaults to avoid root issues, which is something the policy will cover.
Strategy team leader, Ben Baird, says the approach to developing a policy is to recognise the value of trees, “especially in our infrastructure and our subdivision work”.
He says staff will present on the draft tree policy in August.
Professor Morgenroth believes it's worth investing in trees: “Research has shown that for every $1 invested in urban trees, trees will return $3.40 in benefits. “The benefits include, but are not limited to, carbon sequestration/storage, air pollution removal, stormwater runoff mitigation, energy reduction (shade/shelter), and aesthetic value.”
There are other unquantifiable benefits, such as human physical and mental health, as well as biodiversity, he adds.
“Increasing canopy cover will require planting, but that will take time. Limiting the removal of existing healthy trees is also a means of increasing canopy cover through growth of existing trees, or at least not reducing cover.
“Tree protection regulation is limited in New Zealand to individual trees listed in district plans, so regulatory approaches - unless they are changed - for retaining existing trees aren't likely to make a large contribution to maintaining or increasing canopy cover,” he says.
