Insect: Endgame

With a snap of our fingers, humans have doomed 40% of the world’s insects. Move over Thanos there is a new villain in town.

A newly published international report found that 40% of the world’s insects are declining and could be extinct in a few decades!

This collapse in the world’s insects has been reported in the news a lot recently but it always feels very distant. This couldn’t happen in Godzones, 100% pure New Zealand could it?

Insects have such a critical role in our lives, without them, crops would die; and species reliant on them would starve. Insects are part of a huge food web where they provide an essential role, eating smaller things and being eaten by bigger things. Missing this key connector in the food web will be disastrous. We are at a critical time in the future of our species and planet, it’s time to change and try to undo the damage we have done.

“Insects don’t need us we need them”

Why insect populations are plummeting—and why it matters
National Geographic
Eucalyptus tortise beetle
Eucalyptus tortoise beetle
Jon Sullivan (CC BY-NC 2.0)

With the first meeting in Paris for the Intergovernmental Science‑Policy Platform on Biodiversity and Ecosystem Services meeting early in 2019 (catchy name I know), heads of nations from across the world met to discuss the state of international biodiversity and produce its first report since 2005. This meeting reported on the issues facing our planet and the poor state of global diversity. As good as these conferences are I think the average person struggles to relate to the findings as they seem distant. For example, people know the Amazon is getting cut down at an alarming rate but will often think that’s far away and someone else’s problem. These problems must only exist in poor countries, not in clean green New Zealand.

A recent paper lead by Lincoln University researcher Mike Bowie brings the decline of insects into focus with a local context. The researches surveyed ground beetles in Ahuriri reserve in Banks Peninsula and compared it to a previous survey, 30 years earlier.

Ahuriri Scenic Reserve
Ahuriri reserve
Jon Sullivan (CC BY-NC 2.0)

Ground beetles were used as the focus for this study because, unlike other New Zealand insects, they are well described, and considered valuable for a measure of conservation and restoration success. In essence, the more ground beetles you have and the more species you find, the healthier your forest is.

The survey was done by using a trapping technique used in many insect surveys: pitfall trapping. A pitfall trap is essentially a cup in the ground for the ground beetles to fall into while walking around the forest floor. These pitfalls were set out in the forest for over a year and were cleared every 14 days. This method was the same as the previous study 30 years ago.

Mike found that, of the 14 different beetle species detected, 12 species had decreased and only 2 had increased over the three decades. Along with this, the total catch of beetles was 17% lower than the previous study.

The two species that had potentially increased were Holcaspis intermittens and the Banks Peninsula endemic species Holcaspis suteri but this increase was not statistically significant.

Of the six species absent from the latest survey, three of these are endemic to Banks Peninsula Onawea pantomelas, Zabronothus striatulus, and Bembidini sp., along with one endemic to the Canterbury region Oopterus laevicollis.

These reports are disturbing as they identify that the Ahuriri Reserve is one of the highest quality remnant forests on the Port Hills. All the species that they found in the 1981 study were present in the latest study with no new species present and the loss of six species. The loss of our endemic species is of the greatest concern.

What could be causing this decline?

In the reserve there has been the ongoing presence of mammal predators, this could have caused the decline of beetle numbers. There have been high catch numbers of possums, rodents, hedgehogs, mustelid, and cats, Even at lower numbers these mammals can significantly predate on ground-dwelling insect’s.  Another possibility is that the habitat has caused a change in the distribution and counts of the beetles. Historic habitat loss can result in extinction that is delayed for many decades before local extinctions begin. We could be sitting on the verge of collapse due to the fragmented nature of our remaining reserves on the Port Hills. The poor ability for the large flightless ground beetles to move between theses reserves may have sealed their fate. This was seen in the collapse of ground beetles in Manawatu.

One of our native insects at risk to mammal predation
Epitree (CC BY-NC 2.0)

Unlike in the movies we can’t rely on the environmental Avengers assembling and coming to save the day. We need to take heed of the warnings and look to conserve what we have left.

 Luke Sutton is a postgraduate student in the Master of Pest Management. He wrote this article as part of his assessment for ECOL 608 Research Methods in Ecology.

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