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Protecting our precious places

Fencing bush margins

Fencing a natural area as part of the covenant process is the single most important capital and ecological investment that a new covenantor faces.

Studies on the impact of stock intrusion into bush fragments by Landcare Research on the AgResearch Study Farm at Whatawhata are overwhelmingly conclusive regarding the impacts stock cause on seedling regeneration, species diversity, canopy cover and tree roots. The study concluded ‘the outlook is bleak for grazed fragments’.

Building and maintaining fences is not cheap. Without careful planning, a poorly placed and designed fence can cause considerable grief with ongoing maintenance and repair.

Gerry Kessels, an ecologist, claims he has heard almost as many opinions on what is the ideal fence design around a natural area as there are covenants.

Factors influencing the type and location of a covenant fence include the stocking regime, topography, location of adjacent natural areas and the budget.

For example, for a dairy farm on flat country, three electric wires and 8m spaced posts may be perfectly adequate.

Whereas, for a steep hill country fragment at the back of a large station, a 7-9 wire post and batten fence is probably desirable.

Bill and Sue Garland farm on the slopes of Maungatautari in the Waikato. Bill is a second generation covenantor, his father originally protecting the first lowland hardwood bush fragment on their property in 1983. The farm now has 15km of fenceline around bush margins and another 5km around woodlots.

Photo below: A landscape view of the Garlands’ farm, on the slopes of Maungatautari, Cambridge.
The Garland's farm on Maungatautari

With 40 years of fencing experience, Bill offers the following advice:

Bulldoze fencelines

  • Bulldozing where possible ensures a more robust fence that stands up better to stock pressure.
  • Fence repair and replacement is also much easier.
  • Soil build-up on a hand-dug line can be a problem where a fence is on a hill slope.

Angles

  • Where the fence follows land contours, consider putting in more angles rather than bulldozing straight lines.
  • On Bill’s farm, the bushline fences have, on average, one angle every 40 metres.
  • It works out cheaper to use No. 2 eight-foot strainers as angles and put in a faceplate rather than stay each angle.
  • On sharper angles, tiebacks or stays may be necessary.

Space posts

  • Space posts a maximum of 3.8m apart.
  • Place round side to the wire. This makes it much stronger and easier to drive straight and reduces corrosion of the wire as there is less contact with the post.

No batten fences

  • It is far easier to maintain a fence without battens around a bush margin.
  • Where a tree or branch may break wires on a conventional battened fence, plain wires tend not to break. They can be re-stapled and tweaked up easily, especially if permanent wire-strainers are used.
  • When not using battens, electric wires are essential if cattle pressure is likely to be high. While the odd lamb hopping through a fence is not a problem, cattle will put pressure on an unbattened fence unless it has at least one hot wire.
  • Using a 4-wire, all electric fence will not save a lot in cost. There is only a small saving over an 8-wire (2 hot) unbattened fence.

When crossing a creek or boggy area

  • Where practical, put in a crossing or culvert rather than spanning the wires across.
  • Posts can be driven into a firm base which makes servicing easier.
  • Check with your regional council first about the need for a resource consent for a culvert.

Driving a fence line

  • This is significantly cheaper than hand-digging post holes.
  • Driven tiebacks are cheaper and quicker than conventional stays.

Stick to the margins

  • Try and avoid building a fence through bush and stick to the margins where possible.
  • A fence on the margin is much less prone to windfall damage than one within bush.
  • Bush margin vegetation is less wind prone as vulnerable species have usually already fallen. There is also only one side from which a tree can fall, whereas within the bush trees can fall from any direction.

Price and quality variations

  • Shop around for prices as there can be large variations.
  • Bulk orders can get substantial discounts.
  • Always use good quality wire and posts.
  • Get quotes from several local fencing contractors.
  • Estimate the length of the fenceline correctly.
  • Do it once and do it right the first time round.

Relative costs for some different fence types

These examples are practical cost-effective fencing for bush margins.

Costs will vary depending on the terrain, materials and labour.

Bush margin  Fence type  Relative cost
Dairy and beef/ flat country  1-wire electric: 2.3mm wire, No. 2 round posts, 8m spacing  Lower
   Each additional wire

 ?

Sheep and beef/ hill country  5-wire (3 electric), no battens  Medium
  8-wire (1 electric), no battens: 2.3mm wire, No. 1 round posts, 4m spacing, bulldoze line and driven

 ?

  8-wire post & batten: 2.5mm wire, No. 1 round posts, 4.5m spacing  Highest


Open SpaceTM Magazine No. 58 September 2003 © QEII National Trust

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