Over the Fence

(Published in the Tree Grower, the Journal of the Farm Forestry Assn.)

At the start of the 20th Century virtually 100% of New Zealand's timber was won through the exploitation of our natural forest. Today the position is completely reversed with our wood production coming almost entirely from plantation forest.

Further, that production is well in excess of our domestic requirements and the forest industry is poised to become our biggest export earner. This puts New Zealand in a unique position as well less than 10% of world timber production is harvested from plantation forest.

So we have two extremes of forestry in New Zealand. On the one hand we have a monoculture, utility plantation estate, almost all of it being that extraordinary species Pinus radiata, highly managed and clear-fell harvested after about 30 years. On the other we have a substantial portion of the country in natural indigenous species under legal protection.

But what about the middle ground? The farm forestry fraternity has been willing to practice a wide range of innovative regimes, but otherwise mixed and high-value species regimes, sustainably harvested, have been largely by-passed in New Zealand's forestry thinking.

Can we learn here from the forestry culture of older societies that have established highly ethical forestry practices? I think we can, and that we can do no better than to look at the forestry ethics and traditions of Central Europe.

The Germans and Swiss have a forestry tradition called Plenterwald (sometimes known as Plenterforest or Plentergarden). Plenterwald is a mixed-age, mixed species forest with no beginning or end - that is, it emerged from the natural forest and, being sustainably harvested, is perpetual. (Mixed species includes both hardwoods and conifers, with the former dominating the lowlands, and the later the uplands.)

The forester selectively harvests individual trees just at the appropriate time. He is not concerned with its age, but makes his decision on instinct and skill that has been passed down through generations of foresters.

A key factor in management is the effect that the removal of a tree will have on its neighbors. The inferior tree is kept for as long as it aids the form of the superior tree. When it is starting to compete excessively it is removed and utilised to the best value.

The superior, or target tree, is then kept until it is at the optimum stage to harvest for high-value usage.
The discipline of the forester is impressive. If it takes two or even three hundred years for the tree to reach maturity then that is what it gets.

These forests are particularly attractive. The hardwoods bring the seasonal colour dynamics of the deciduous tree and blend with the diverse forms and textures of the conifers. They are greatly valued for the way they enrich the landscape and their recreational importance, and environmental protection, as well as providing timber in perpetuity.

Can we replicate the Plenterwald concept in New Zealand with exotic species? I believe we could, and we should seriously consider it. With our growth rates it could reach a state of equilibrium in maybe six or seven decades. (It is a myth that rapidly grown hardwoods are of inferior quality. This is not so, but in New Zealand we have not applied the silvicultural practice that they warrant, but which we have taken to such exacting standards with our pine forests.)

Unfortunately in commercial terms it would not compete with the ebullient pine, but then generally no form of forestry does. Therefor the non-commercial motives, the emotional values - amenity, recreational and environmental/ecological - need to be considered and promoted.

But what of the merit of moving selected areas of our indigenous forestry into a sustained management regime like plenterwald? Well, of course new Government policy has precluded this option.

Many, including forestry scientists and environmentalists, argue that this plenterwald-like regime is an enlightened path of the future and warranted at least a period of evaluation in limited areas. It will now be difficult for a future government to reverse this policy, as it will inevitably be subject to the slander of 'environmental vandalism' by political opportunists and ecological fundamentalists. (In the meantime New Zealand continues to import hardwood that is often unsustainably harvested.)

We could of course start from scratch and plant suitable native species with the intention of managing them for eventual harvest, but there are problems here too. The first is the obvious one that it will take perhaps a century for such a project to come to fruition. This is not considered unduly long by world standards, but is so by this country's inevitable benchmark, which is the 30-year pine rotation. It must be remembered that such a forest provides biodiversity of habitat and opportunities for recreation throughout its continual life.

Indeed, there are practical examples that appropriate native species under favorable plantation situations have encouraging growth rates. Given their high timber value and otherwise unobtainability this forestry option demands serious consideration. A good illustration of the possibilities is a grove of kauri planted on an average quality site (but with a very advantageous climate) at Pukekura Park in New Plymouth in 1936.

These trees have done very well, but their growth is now being impeded through excessive stem numbers per unit of area. It will, though, require a brave man to advocate taking a chainsaw to them and culling the poorer specimens, but that is what they need for them to realise their full potential. This is the plenterwald philosophy, although in this case the prize is the amenity worth of the remaining trees.

Another example I know of is a street planting of totara carried out in the 1920s in the flat Napier suburb of Napier South. Unlike the Pukekura kauris, they have not been subject to competition, but for most of their life have suffered the indignity of having the tops hacked back to keep them short of overhead wires. They therefor have no form but have grown vigorously nevertheless with girths of up to one metre.

These are two species that are superb carving timbers and naturally durable. They are our primary species used for indigenous ethnic art. Where are we going to get such material from in the next century?

There are many exotic species of high value that grow very well in New Zealand, like walnut, oak, and a number of eucalyptus species. Their wood can be applied to many special uses, but by definition they do not qualify for Maori art, at least in pure terms.

But there is another factor than growth rate which mitigates against this type of productive indigenous forestry and that is the lack of confidence of would-be growers (mostly farmers) that the future owners of the land will be permitted to harvest them.

Given that eventual harvesting is the very motive for planting the trees in the first place, is it a reasonable fear that a government a century hence will legislate to prevent harvesting, or see such a plantation regime in similar terms to natural indigenous forest? I think that it is entirely understandable, but, whether or not it is justified, it is a real impediment nevertheless.

What we need is a legal protection attached to the title that provides the landowner prepared to consider this regime with an assurance of right-to-harvest. Certainly it will have to be something a lot more binding than an 'accord'. Perhaps something like a mirror-image of the covenant which has been so enthusiastically embraced by landowners over the last twenty years, especially through the assistance of the Queen Elizabeth II Trust, to protect in perpetuity bush and other valuable natural areas on private land.

Since colonial settlement New Zealand has developed a pastoral culture of world regard, but it has been at the expense of our forests, both in practice and in emotion. Over the last generation this has happily changed with a massive increase in our productive, but (mostly) one-species estate, and with a much greater regard for our indigenous biodiversity.

But there are many manifestations of forestry practice, some of which we are developing. Certainly we should give greater consideration to the sustainable productive forest than we are currently doing, and it should be either exotic or native, or, for that matter, a combination of the two.