environment

Dairy conversion threatens rare beetle habitat

The home of a threatened beetle is being replaced with 14,000 cows as part of a dairy conversion.

Only 10 Eyrewell ground beetles have ever been found. The five most recent finds have come from a pine forest north of Christchurch belonging to Ngāi Tahu which is to be removed and the land converted to dairy farming.

Conservationists believe this spells extinction for any remaining beetles.

Featuring on the Department of Conservation’s (DOC) draft threatened species the Eyrewell ground beetle is one of 150 species listed as a conservation priority. Its precarious situation has been known for some time.

“I fear the relationship between the department and Ngāi Tahu became probably more important than the beetle I’m sad to say."

Forest & Bird's group manager conservation advocacy Jen Miller said the fate of the beetles has been raised on several occasions over the years.

“For some time, a ranger from the Department of Conservation tried very hard to engage Ngāi Tahu, the department and the forestry company that was contracted to cut over the forest.”

She said her questions on a plan to save the beetle from extinction were never answered by Ngāi Tahu and she is unaware of any efforts to save the beetle since she was involved.

“I fear the relationship between the department and Ngāi Tahu became probably more important than the beetle I’m sad to say.

“That has weighed on my mind. It may have meant the extinction of the beetle itself.”

The ground beetle originally lived in kānuka forest, however, when that was burnt off to make way for plantation forestry it adapted to live in 7000 hectares of pine.

"It was a very effective method of not only shredding any plant matter, but any invertebrates that are larger than a pinhead."

The pine forest was returned to Ngāi Tahu in 2000 as part of a treaty settlement. Its plan was to convert the forest to irrigated land for diary farming.

The beetle’s fate was raised this week by Wikipedian-at-large and keen entomologist Doctor Mike Dickison after Stuff published an article confirming the last of the Eyrewell Forest was due to be felled.

Dickison said scientists originally started surveying the forest in 2000 after the first pine felling occurred. Before this survey only two specimens of the beetle had been found and identified.

“They knew it was somewhere in the forest, so they spent years setting up pitfall traps. They caught thousands and thousands of beetles but only five of this one.”

Little is known of the beetle. Around 10 to 11mm long, it is shiny, black, nocturnal, and is thought to have a life-span of two years. Without wings and described as a “moderate runner” it’s thought to have little chance of moving to a new area.

Eyrewell ground beetle. Photo: Birgit Rhode / Landcare Research – Manaaki Whenua CC BY 4.0

All five beetles were found in three spots within the forest, identified in a paper published in the New Zealand Journal of Ecology on the beetles.

Dickison has compared maps in the paper with satellite imagery.

“The saddest thing is now looking at satellite maps is the deforestation is going on at a frantic pace. Two of the three spots they found the beetle are now cleared and are part of a centre-point irrigated dairy farm. What’s left of the forest is chopped into little chunks. There’s surprisingly little left of the forest. They’re going at it at a cracking pace.”

There’s a chance the beetles are already gone, but Dickison believes emergency surveys should be done of the fragments of pine which remain and if beetles are found the forest should be retained.

The lead scientist of the study, Eckehard Brockerhoff said he has considered writing an obituary for the beetle.

His description of the dairy conversion process is stark.

“It involves felling all the trees, ripping out the root stock and then pretty much mulching the coarser woody material which is left behind into small chips. They took like a giant shredder over it. It was a very effective method of not only shredding any plant matter, but any invertebrates that are larger than a pinhead. I didn’t think the beetles would have stood much of a chance to survive in those converted areas.”

Brockerhoff said he engaged with Ngāi Tahu and DOC when he was doing the research.

“We had a good three-way conversation, with DOC in Christchurch and Ngāi Tahu properties. We discussed the issue and brought it to their attention and looked at possibilities - what could be done to provide some remaining habitat within the conversion.

“At the time they were a bit reluctant.”

Brockerhoff said Ngāi Tahu hoped pine shelter belts which were going to be established between irrigated paddocks would provide enough habitat for the beetles.

“We suggested a single row of trees in the landscape established after the habitat conversion would probably not do the trick.”

He believes it’s unlikely the beetle will survive if the remaining area is converted.

Ngāi Tahu was approached yesterday for comment but said it would not be able to respond before publishing. Information on its website suggests 150 hectares of native forest is to be planted on the land as part of a biodiversity programme. It is unknown what stage this is at, or if a plan is in place to encourage beetles to migrate from the pine forest to a new area.

There is little protection for insects on private land unless they are specifically protected under the Wildlife Act, the Eryewell ground beetle is not on the schedule of protected insects.

A draft policy for indigenous biodiversity has been written which would cover biodiversity in significant natural areas. However, Federated Farmers and the Forest Owners Association who were involved in the document's creation want an exclusion for plantation forestry being classed as significant natural areas regardless of whether they are home to threatened flora or fauna.

Read more: 

Sweeping change to stop biodiversity crisis

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