From pines to podocarps

Towering above visitors in the ngahere/forest, the non-native pine trees at Zealandia Te Māra a Tāne were originally planted as a forestry trial as early as the 1880s. Jo Ledington, General Manager Conservation and Restoration, shares some of the thinking that has gone into the removal of these trees.

When I returned to work for Zealandia Te Māra a Tāne in 2022, one of the first projects I was tasked with was “to do something about those pines”. While we are only 25 years into our 500-year restoration journey, it was becoming more pressing to have a plan that would move the valley’s canopy from exotic to being dominated by native podocarps.

As I started getting my head around the scale and complexity of this project, I quickly came to realise that these trees not only had historical value but that these towering trees also brought innate value to the valley. Just standing beneath these giant trees and hearing the neck tingling attack call of the kārearea, seeing kākā roosting, and watching kawau/shags fly by showed me some of the value these trees hold, especially with the absence of our native podocarps such as rimu, miro and tōtara.

Through speaking with experts in pine management and restoration, it soon became apparent that these trees weren’t necessarily the exotic ‘pest’ my western-trained ecological perspective saw them as, but that they were an important piece of New Zealand’s restoration jigsaw. And if that were the case, how could Zealandia do what we are so good at doing and learn, research, and share another perspective of exotic canopy management in New Zealand? The answer was, of course, in collaboration.

These conversations with experts soon led me to David Spencer, Managing Director of Tend Trees Ltd, a consultant arborist who lives and breathes trees. I outlined one of my key considerations to David on a walk along Valley View Track—how could we remove these trees cost-effectively (aka, no helicopters!) without damaging the regenerating forest and animals now living beneath the towering exotics?

David asked if I’d heard of a technique called ‘veteranisation’. This is the process of creating habitat which would happen naturally in old trees but in younger trees and at an earlier stage than would naturally occur. David had been involved in early trials of this technique with Wellington City Council. We both felt there was an opportunity to use the years of hands-on species management knowledge at Zealandia to inform New Zealand-specific veteranisation techniques and monitor the outcomes to be shared with both ecologists and arborists across the country. These methods are commonly used internationally and practitioners in the UK, USA, and Australia have species-specific technical information available to them—could it be possible for us to create this for New Zealand?

In 2023, we trialled the first veteranisation techniques at Zealandia, including constructing nest cavities for kākā. Excitingly, three of the six nests constructed were used and one female successfully raised three chicks in the nest. Interestingly, this female was an older kākā who had never deemed artificial nestboxes suitable for nesting! Early results from monitoring these nests were also encouraging for nest health, with fewer mites present and temperature regulation of the cavities less variable than artificial nest boxes—both measures that result in stronger, healthier chicks. More veteranisation work will be carried out this winter and the long-term options are endless. We will continue experimenting with nest cavities for different species, using branch cuts that encourage fungal and plant growth and increased decomposition, and the planting of epiphytic plants in tree forks to increase canopy diversity.  

For me, this work has been yet another fascinating lesson about the complexity of nature and the importance that different perspectives and collaboration bring to finding the best result.  

Who would’ve thought a gnarly old pine tree would be such a wise teacher?

Photo credit: Zealandia pines by Melissa FT