OPINION: Tahr present threat

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New Zealand alpine vegetation evolved over millions of years in the absence of large mammalian herbivores.

The Southern Alps/Ka Tiritiri o te Moana ecosystems are therefore particularly vulnerable to sudden interference from introduced browsers such as tahr and chamois.

Tahr were introduced for hunting in 1904, and now occupy about 9600sqkm of the Southern Alps.

Herds of these herbivores not only trample large areas of vegetation, they rely on New Zealand’s fragile alpine plants for nourishment.

Tahr devour snow tussock, at times killing entire plants.

Thirty percent of their diet consists of grazing on natural grasses, and browsing on leaves and fruit of alpine herbs, such as mountain daisy, spaniards, the Aoraki/Mt Cook buttercup (a favourite), as well as sub-alpine shrubland species.

Worse still, the damage and elimination of plant cover affects other animal species that rely on the same food source.

This results in decreasing soil nutrients and deteriorating soil cover.

Ines Stager

While natural erosion occurs in these environments, this is made worse by the inability of native alpine plants to grow, and soils in such harsh environments erode more rapidly.

This is exacerbated by increasing and extreme weather events as a result of climate change.

From a conservation point of view, the alpine environment would be much better off without Himalayan tahr.

According to the tahr management plan (1993), the total number should be kept at 10,000 animals.

The plan also includes monitoring of mountain grasslands throughout their range, to determine the long-term impacts.

This process consists of a representative network of 111 permanent vegetation plots.

The total agreed figure in the plan is still a large number of animals, especially if we compare that with several of our threatened animal species, for example Maui dolphin, kakapo, and kaki.

However, the actual figure of total tahr in the Southern Alps now exceeds the agreed figure by 3.5 times. Tahr are now even seen low down in the South Canterbury foothills.

Hunters and commercial guides look at tahr from a different angle. They consider it as a resource. Individuals and groups interested in hunting and guiding have made their opinion known recently when the Minister of Conservation signalled that a major cull needed to be undertaken immediately.

Meanwhile, tourism is rapidly increasing, and it can be argued that the number of tourists admiring buttercup at Aoraki/Mt Cook is much larger than people benefiting from hunting tahr.

It is surprising there is such a reaction to a necessary cull of tahr in order to protect key biodiversity values that are also a “tourist resource”, and yet support to save native species seldom attracts the same amount of activism.

Ines Stager is a landscape architect based in Geraldine, a board member of the Royal Forest & Bird Protection Society and a committee member of the local branch.