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  Environment » Natural Resources » Biodiversity » Forest fragments » Managing forest fragments » Fencing fragments

Fencing fragments

Photo of cow next to fenced forest fragment. Most of the 7500 native forest fragments in the Waikato region are on privately owned pastoral land. Most are not fenced, and are regularly damaged by stock. The first priority for all forest fragments should be to keep stock out of them permanently.

On this page: Stock damage, Benefits of fencing, Fencing tips

Stock damage

Unfenced fragments on farms can suffer a lot of damage from livestock. New Zealand’s plants and animals evolved without any large grazing mammals. Our soils and plants can’t cope with the trampling, grazing and waste from stock.

Cattle, goats and, to a lesser degree sheep, with free access to a fragment will heavily graze edible native seedlings and saplings, opening up the forest underneath. Livestock can also weaken, and sometimes kill trees by rubbing against trunks and trampling roots. Fragments continually visited by stock will become a stand of sick, old trees, with no young plants to replace those that die out. Eventually the whole fragment will collapse.

Damage from livestock can also decrease the water quality of fragment streams, affecting the animal life within them.

However, stock damage may increase the risk of fire as vegetation under the trees is eaten. The area can become open, breezy, and dry with an increased build-up of broken branches and dead trees. Keeping stock out may result in weed growth, but most non-invasive weeds will die within a few years as native plant growth blocks out their light.

Benefits of fencing

Some Waikato farmers have discovered that keeping livestock out of forest fragments benefits both the fragment, and farm management overall.

Fencing stock out of forest fragments:

  • reduces soil erosion and compaction
  • prevents damage to bark and roots
  • makes mustering stock easier
  • stops too many nutrients coming into the fragment through stock faeces and urine
  • increases seedling and shrub survival
  • maintains a cool, shady forest interior.

Keeping stock out of waterways that pass through fragments:

  • reduces stock losses
  • reduces sediment and nutrients in fragment streams, rivers and ponds
  • makes better natural homes for aquatic animals.

Healthy, ungrazed forests have dense native undergrowth, a deep leaf litter layer, and thick shrub, sedge or flax margins. They filter out sediments and nutrients from rainwater and water running off from surrounding land, and reduce erosion during heavy rain. Fragments with an open understorey and bare earth can’t do this, and may, in fact, contribute to the loss of sediment.

Find out more about how grazing affects wetlands.

We provide advice and support for efforts to reduce the impacts of farming on waterways through fencing and planting waterway margins. Find out more about our integrated catchment management services(external link).

Fencing tips

Here are some suggestions to help you protect your fragment from stock:

  • Use eight wire post and batten fencing for effective sheep and goat control.
  • A well maintained two, or three wire electric fence will exclude cattle.
  • Put in a gate so you can get any stock breaking through the fence back out again quickly. In just half an hour, stock could undo years of plant regrowth in restored fragments.

For fragments which are small, open underneath, and/or exposed to wind:

  • Place the fence five or more metres away from the bush edge. Between the fence and the forest, plant up a buffer zone of hardy shrubs and small trees.
  • If you can’t, or don’t want to plant a buffer zone, place the fence under the dripline close to the bush margin to reduce weed invasion.

Shelter for stock is important, but with a tall forest stock can seek shade beside, rather than inside the forest. You could leave a few trees outside the fence, at least until shelter trees in the paddock are big enough.

Find out more about managing and restoring your fragment, and controlling pests and weeds.

Check out our planting guide using our list of species.

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