Governments around the world are being warned more must be done to prevent declining insect numbers, or the consequences could be severe and wide-reaching.

Photo: 123rf

More than 70 scientists from 21 countries have written an appeal for immediate steps to reduce threats to insect species, and a roadmap to recovery, which has been published in the journal Nature Ecology & Evolution.

"There is now a strong scientific consensus that the decline of insects ... and biodiversity as a whole, is a very real and serious threat that society must urgently address," the group said.

Waikato University's Dr Christina Painting contributed to the text, and said a decline in insects could mean "big trouble" for humans because they were crucial to agriculture and healthy ecosystems.

Insect pollinators were needed for growing crops, to keep our forests healthy, and insects were the main food source for many of our native fish and birds, she said.

The group have praised the German government for committing €100 million ($NZ168m) to the problem, which they say is a "clarion call to other nations".

What do they say should be done?

Painting said there were smart and achievable steps that could be taken to make an immediate difference.

"They're ideas we think scientists, policymakers, land managers and communities can all use together to help insect conservation."

High on the list is for natural areas to be planned for within urban and "homogenous" environments, which could provide havens for insects, and support species diversity.

Photo: Alison Ballance

"I think in New Zealand we're pretty good and very proactive about trying to come up with restoration areas in both urban and in our conservation estate. But perhaps we haven't really been thinking about what's good for insects while we've been designing those programmes," she said.

The group have also called for "aggressive steps to reduce greenhouse gas emissions, reversing agricultural intensification, including reduced [use of] synthetic pesticides and fertilisers and pursuing their replacement with agroecological measures."

Phasing out pesticides could be one of the trickiest challenges, but it was important to start, Painting said.

"There are problems because they're generally not that specific in the species they target - so if you put a broad-spectrum pesticide out it's going to knock off not just the pest species you're worried about for your crop, but also anything else that might be there.

"An obvious measure that could be more biological control methods - using other insect species or a pathogen to knock out a pest species, and there's a huge amount of work that goes into developing those species and that research at our Crown Research Institutes in New Zealand."

Light pollution was also on the list, as it could have a "pretty severe" impact on insect populations, she said.

The attraction of man-made lights could lure insects to their deaths, and disrupt normal mating and feeding patterns, Painting said.

"There's lots of light designs now that don't attract insects or birds - because migrating birds can also be pretty strongly affected by light as well."

Photo: Supplied.

The extra steps needed for New Zealand

Painting said in New Zealand we faced an extra complication - we knew so little about our insect populations compared to the Northern Hemisphere, that we just didn't have a good grasp of the problem.

New Zealand is thought to have about 20,000 insect species, but only about half are known to science (or described).

There was strong evidence for significant declines in many species around the world over a long period of time, and it was likely the human-induced changes animals were susceptible to were affecting insects here, she said.

"We don't really know what's happening to our insect populations ... we really lack long-term monitoring data to comment suitably. We need to figure out what's actually going on here, and how complex that problem might be."

What is being done in New Zealand?

Painting said work was being done by the Department of Conservation to prioritise the most threatened insect species we really need to worry about and act immediately to conserve.

"Things like the giant weta, various moth species, and some threatened flightless beatles - there's work and money being put into those species recovery programmes now.

"We're not doing nothing, but the biggest problem in New Zealand is the lack of that longer-term data - because the way we do research tends to be within a research programme that is usually only a few years long. So we lack the ability as researchers to collect data over the longer term, which would really give us answers about what we need to really worry about."

Photo: Landcare Resarch CC-BY 4.0

She said more support was needed from the public and for government to recognise just how important insects ewre.

"We fund things that people value, and to date there has been a much lower appreciation of insects than other species, so it makes sense that we've seen less money put into insect conservation."

More public education could lead to more appreciation for insects and the roles they play - and then should translate to more justification for policy-makers to commit funding to protect them, she said.

"Some of us think insects are gorgeous and very cute, but it's crucial to understand that without them we'd be in big trouble - they're just so incredible because it's such an intricate system of interactions between different species and within communities - and we're just in our infancy of understanding just how those pieces together.

"Those questions and the mystery around that alone, I think, is something we should really be excited about."