Dairy expansion in Mackenzie basin threatens weta and grasshoppers

The "march" of dairy farming across the Mackenzie basin has threatened the survival of local weta and grasshopper ...
TONY JEWELL/FAIRFAX NZ

The "march" of dairy farming across the Mackenzie basin has threatened the survival of local weta and grasshopper species, found only in the area.

The "march" of dairy farming across the Mackenzie basin is threatening local weta and grasshopper species, a Department of Conservation (DOC) science advisor says.

It follows a threat level reclassification of some Orthoptera species in New Zealand by the department, such as crickets, grasshoppers, and weta.

Two species found only in the Mackenzie basin, a ground weta from the Hemiandrus genusĀ and a grasshopper Brachaspis robustus, were recently classified as "nationally critical" in the report, the highest threat level.

Spotted a few kilometres south of Lake Tekapo earlier this year. The species of weta are sometimes referred to as ...
TONY JEWELL/FAIRFAX NZ

Spotted a few kilometres south of Lake Tekapo earlier this year. The species of weta are sometimes referred to as Hemiandrus furoviarius, or Tekapo weta, but they have no formal name, according to Massey University ecologist professor Steve Trewick.

DOC invertebrate ecology technical advisor Warren Chinn said both species were increasingly in trouble because of loss of "real estate".

"Where it lives, and how it lives, is disappearing," Chinn said.

"The march of dairying across the Mackenzie basin is reducing habit for rare and endangered invertebrates."

Massey University ecologist professor Steve Trewick, who co-authored the report, said the ground weta burrowed underground and were sensitive to "land use".

In areas where soils were "modified" by chemicals, fertilisers, and irrigation, ground weta and other native invertebrates using the habitat "tend to be scarce".

It was part of a general pattern across the country, which had seen the loss of lowland habitats.

"In many cases, we simply do not know, and cannot know what has been lost."

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Upland habitats faired better because they were less attractive to agriculture, he said.

Trewick said the area needed more monitoring of native habitat and cessation of modification activities.

However, Chinn said despite "being on the edge", the species had a chance at survival.

The basin was "particularly unique", ringed by mountains with low humidity and rainfall, which had isolated some species and their evolution over generations.

He said it was "perfect" for a for a dryland park area.

Increasing protected land area for native species, including birds and fauna, could help species to thrive, he said.

The weta was an ambassador for these issues, and a "textbook" to learn about biodiversity.

"It's information and knowledge the community can reflect on. If we don't maintain variety of life, it's not as rich of an existence to people."

 - Stuff

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