Eucalypts: Sustainable timber

Organic NZ Magazine: July/August 2009
Section: Building
Author: Philippa Jamieson

Philippa Jamieson investigates a new initiative to grow and use versatile, hardwood eucalypts

Do you want to plant a woodlot that will give you durable wood for farm posts and building, give you a return in as little as 16–20 years, as well as sequestering a lot more carbon than pine? Think eucalypts.

But it’s not just any eucalypts – there are specific species that we need to be growing, say Paul and Ash Millen. The two brothers have been growing trees for timber for 25 years. In 2003 they set up Vineyard Timbers at their home in Queen Charlotte Drive, Marlborough, motivated to provide durable, non-treated timber for vineyard posts, thereby reducing the amount of timber treated with CCA (copper, chromium and arsenic) being used in Marlborough’s burgeoning vineyard industry. Environmentalists warn that these toxins leach from timber and build up in groundwater, and the treated timber damages our clean, green image and markets. Furthermore, the poles break easily and environmentally acceptable disposal is difficult.

So the Millens sourced eucalypts from both the North and South Islands, some from 60-year-old trees, but ran out as there simply weren’t enough trees of the right kinds (see sidebar). They then realised that they would have to start growing the right species, and helped establish the New Zealand Dryland Forests Initiative (NZDFI), a collaborative, cross-sector research and development project (see sidebar). The Millens are commercially propagating seedlings, and have sold 100,000 in the last few years.

“We’re not really doing anything new,” says Paul Millen. “We’re just moving back to what people used to do.” Once the valuable native New Zealand hardwoods like totara and kauri were logged from accessible areas, there was interest in Australian eucalypts in the 1930s and 40s. However by the 1950s CCA was developed and interest in eucalypts waned, and radiata pine became the dominant timber tree.

Multiple uses
But Paul says that if we grow the right kinds of eucalypts they can be used for so many things: vineyard and farm posts, high-quality furnishing, flooring, and specific uses such as the cross-arms in the electrical lines industry (pine is not strong enough). “You can build a whole house out of eucalypts,” says Paul.

Having timber you don’t need to treat makes everything much simpler, and makes huge savings, particularly in the processing of timber.

“Eucalypts are highly suited to small growers who want to put a woodlot in and be more self-sufficient,” says Paul. “The trees can be thinned for your own postwood, then later on you can bring a mill onto the property and mill the timber for your own use.” Usable polewood should be produced within about 8–10 years, provided there is sufficient heartwood growth, and in about 16–20 years the trees can be milled for small diameter saw logs.

Paul and Ash Millen are also interested in growing cypress species such as macrocarpa, which are allowed for use in the building code (framing, external cladding as well as internal use). Paul says the building code needs to be altered to reflect the use of appropriate eucalypt species as well.

 

Sourcing seed

Unfortunately the six kinds of eucalypt identified as having strong and durable timber have been heavily logged in their native Australia, with small remnants remaining in national parks and public reserves and some private land. This means that there are some difficulties in sourcing seed, but Proseed (one of the NZDFI partners) is working with Forests NSW to source seed from breeding programmes, as well as organising collection from the wild.

Mitigating climate change
Growing the right kinds of eucalypts will also help mitigate climate change emissions, by sequestering carbon at faster rates than radiata pine. Also, it will help us cope with the effects of climate change – in particular the regular periods of drought occurring in eastern parts of New Zealand – as eucalypts are hardy and able to withstand drought. Being able to grow more of our own hardwood would reduce the need to import hardwoods, and therefore reduce the possibility of importing, unsustainably (and sometimes also illegally) logged timber from tropical rainforests.

 

Durable eucalypt species
Paul Millen has tested about 20 species, and found at least 10 that grow well in New Zealand and are of suitable durability and strength for multiple uses, including high-quality timber for building and furnishing, as well as in-ground as posts.

The six species selected for trials by the New Zealand Dryland Forests Initiative are:

  • Eucalyptus bosistoana (coast grey box)
  • E. argophloia (western white gum)
  • E. camaldulensis (red river gum)
  • E. quadrangulata (white-topped box)
  • E. macrorhyncha (white stringybark)
  • E. globoidea (red stringybark)

For more information on these species, refer to www.nzdfi.org.nz

 

New Zealand Dryland Forests Initiative
The NZDFI was established in 2008. It is investigating and promoting the planting of genetically improved (but not genetically engineered!), naturally durable eucalypt forests and woodlots on drought-prone and erodible pastoral land. The work of the NZDFI is based in Marlborough and Canterbury.

Members include: the Marlborough Research Centre Trust, Marlborough District Council, New Zealand School of Forestry (University of Canterbury), Marlborough Lines, Vineyard Timbers Ltd, Proseed NZ Ltd, and a number of rural landowners.

Additional funding comes from AGMARDT (Agricultural and Marketing Research and Development Trust), the Neil Barr Farm Forestry Foundation, and other interest groups including Marlborough Tree Growers Association, the New Zealand Farm Forestry Association’s Eucalypt Action Group, and Organic Winegrowers New Zealand.