Trees are on the job for us, 24 hours a day, seven days a week, working to improve our local neighbourhoods and our wellbeing, and helping to mitigate the effects of our changing climate.
\Earlier this year we adopted the Urban Forest Plan for Ōtautahi Christchurch. We’re wasting no time, putting that Plan into action. To make the most of some government funding, and the remaining time left in the 2023 planting season (which runs from April – September) we’re fast-tracking tree planting plans for 14 parks and reserves across Christchurch and Banks Peninsula.
We’ve chosen at least one park per community board area, and then focused specifically on areas (such as Linwood and Hornby) where we know the tree canopy cover is low and needs to be increased.
Species
These plans don’t go into detail about the exact tree species that will be planted. That’s because we need a little bit of flexibility to accommodate fluctuations in tree availability. However, we have a target of between 40-60% native species, as well as prioritising natives along any waterways.
And we’ll be guided by the Urban Forest Plan’s principle of ‘right location, right tree, right function’ - trees are grown in locations that allow them to reach maturity and benefit the local environment.
Tree species diversity is important to maintain a healthy tree population. The greater the diversity, the more resilient our urban forest will be to threats – particularly the effects of climate change, and pests and disease. Ideally, we need no more than 30% from one family, 20% from a single genus or 10% of trees from a single species. We also need to take steps to protect the natural diversity of our local indigenous fauna through the use of locally-sourced plants.
Size
A range of tree sizes is also important. With bigger canopies and root systems, larger trees maximise benefits such as carbon sequestration, stormwater management and shade. However, smaller trees are also valuable in places where space is restricted.
We’ve listened to feedback from residents and have designed these tree planting plans using a recession plane model, so we can manage the impact of shading on neighbouring properties and sports fields. The plans show shading at different times of the day at summer and winter solstice – importantly, they show how the plantings won’t cause all-day shade.
We’ve also set the trees back from infrastructure such as paths and property boundaries to avoid any encroachment problems in the future.
We’re aiming for 40% canopy cover across our parks. In some parks this will be higher, and in some parks lower, depending on how the park is used and the space that’s available for planting. For example, in parks which don’t have sports fields, we’re making sure we retain some open spaces.
While we’re aiming to get as much as we can done in this planting season, planting within each location will be progressive and not necessarily involve planting all trees shown in a plan within a single season. Trees may be planted over a few years, subject to tree availability.
This is also just the start of a huge programme of work. We have more than 1200 parks and reserves across Christchurch and Banks Peninsula and clear targets for increasing tree canopy cover over the next 50 years, so from now on, we’ll be targeting up to 60 parks each planting season.