Pest control fences

The invasive species in New Zealand are the main threat to the native biota. There are 31 species of invasive mammals in the island. People in New Zealand are mixing the use of tramps and fences. The fences are used to prevent invasive species to enter a conservation zone and the tramps to eliminate them from the area. In small islands near the main island the use of tramps has been a great success. 28 natural reserves are surrounded by fence with a total of 8,396 ha. The fence also serves as barrier to the wild life fauna to leave the secure forest such as the brown kiwi Apteryx mantelli. The fenced areas now serve as sanctuary of threatened species after the reintroduction of threatened species such as Notornis mantelli. In the case of the Chatham petrel Pterodroma axillaris it was only known to have one place of breeding in Chatman Island and now it has been introduced to a fenced reserve hoping to create a second breeding place. When a fence crosses a flow of water it is interrupted to allow the free pass of the water. When at low flow the fence closes the gates to prevent the crossing of fauna with low flow. The fences are also used in Zoos.

The use of a fence is controversial because a fence can also avoid the movement of animals from one reserve to another. It may change the chemical of the soil around the reserve preventing the underground living animals such as nematodes to cross the fence and increasing the edge effect of those organisms. Another benefit of a fence would be to avoid part of the edge effect of large organisms due to predation. The edge effect is different depending on the species. In new Zealand is needed the fence because the primary threat is the invasive species. Therefore the positive effects of having a fence overwhelm the Negative effects. 

Burns Bruce; Innes John and Day Tim.(2012) The Use and Potential of Pest-Proof Fencing

for Ecosystem Restoration and Fauna Conservation in New Zealand. Fencing for Conservation 65-90

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