|Trees play a large role in New Zealand’s vernacular architecture. It is hard to beat locally grown and harvested native, naturally durable timber to facilitate our demand for sustainable construction.|
The awareness and demand for naturally durable, indigenous timber is growing, as is the distaste of toxic chemical treatments – a common one being chromated copper arsenate. This substance is banned in many countries, but is still commonly used to treat pine here. With Pine being such a key building material, this poses a serious threat to our health . (To learn more about naturally durable timber – specifically Macrocarpa – see our previous post here.)
Together with the growing popularity of chemical-free options, is the increased demand for traceability and sustainable forestry.
There are many environmental risks to the typical method of felling trees, known as clear felling. This is when an entire forest is cut down at the same time, leaving hillsides prone to erosion that can also lead to water pollution .
Sustainable forestry, on the other hand, is all about balance. It is about the extent to which forestry practices mimic natural patterns of disturbance and regeneration. It balances the needs of the environment, wildlife, and forest communities .
The key challenge for sustainable indigenous forestry is to extract timber while maintaining or even enhancing the non-extractive benefits of these forests, such as biodiversity, water quality, carbon storage, and cultural identity .
Sustainable forestry involves selective harvesting or target diameter harvesting, where only a small number of trees are felled when they reach a certain trunk width. Continuous-cover forestry is maintained, leaving the rest of the forest intact with only the biggest trees taken out. This results in less erosion, as there are still trees gripping the soil . Smaller machinery is used so that there is minimal and non-permanent damage to soil and surrounding vegetation .
Tree diameter assessment, Scion
Felling using small machinery, MacBlack
Other regenerative harvesting methods include restoration silviculture. Tūhoe Tuawhenua Trust have been harvesting Tawa in areas extensively milled last century. By restricting harvesting to 30m x 30m areas, they are creating space and light for new podocarp seedlings to prosper. The funds generated from the harvested tawa are then used to facilitate further restoration of the podocarp . This satisfies the dual goals of restoring the plant and birdlife in the forests while also creating an economic resource for future generations.
As a method to see that Aotearoa’s tree planting rate doubles over the next decade, block owners are being motivated to start planting small forests. They will receive grants depending on the size of their blocks and the types of trees they plant. The influx of trees will allow for more carbon sequestration – and so will the timber homes in which we live . Let’s hope for the sake of our biodiversity and general wellbeing, that native timbers are prioritised!
References: thisNZlife. 6 trends to consider when planning a specialty timber crop  Rainforest Alliance. What is Sustainable Forestry?  Landcare Research. Sustainable Indigenous Forestry  MacBlack. Forest
For more information about native sustainable forestry in New Zealand, see: