This feature was first published in December 2016 for the launch of the Wasp Wipeout project.
The wasps' hum, the white noise of the forest, is a constant reminder that they — the foreign invaders — are winning.
They are having a devastating impact on our native birds, bats, lizards and insects, exploiting the most valuable food sources of the forest and entirely altering New Zealand’s natural biodiversity.
These wasps are also a serious threat to people, delivering painful stings that can cause life-threatening allergic reactions and — in extreme cases — death.
The German wasp (vespula Germanica) and common wasp (vespula vulgaris) have been described as New Zealand's most abundant and devastating invertebrate pests.
To appreciate their impact on the environment, and our native species, we first have to understand how many wasps there are.
Studies have found that, at their peak, there can be up to 40 nests per hectare of beech forest.
A nest can produce thousands of queens and thousands of workers, and there are about a million hectares of beech forest in the South Island.
Based on these figures, there could be up to 40,000,000,000 (10 zeros) wasp queens in the beech forest at the height of summer, and many more workers.
Insect ecologist Richard Toft says the impact of that amount of wasps on the ecosystem has “got to be catastrophic”.
“We have a lot of talk about rats and stoats and mice and their impact on systems.
“But put wasps in those same forests, the biomass of wasps exceeds the combined biomass of all the rats, all the mice, all the stoats and all the birds.
“You simply can’t add that amount of biomass into an ecosystem and expect it to have no impact.”
The introduction of foreign wasps has also impacted on the ability of people to enjoy the outdoors in summer.
Picnics, bush walks, and even chores around the home like gardening and lawn-mowing have turned nasty because of wasps.
If disturbed, German and common wasps can deliver painful, venomous stings that causes some people to have allergic reactions, known as anaphylaxis. The symptoms range from pain, swelling and shortness of breath to death.
“For those people, it’s pretty scary,” says DOC Nelson Lakes senior biodiversity ranger Nik Joice.
“They say that when you do have a really bad reaction you have a sense of dread and fear that you’re going to die.”
But just the presence of wasps — their incessant drone — can ruin a day in the outdoors.
“If you’re a hiker in late summer-autumn in beech forest then you are very aware of wasps. You sit down and try and have your lunch and you are swamped. It’s very easy to walk on a nest in those circumstances,” Lester says.
“Compared to what it was in a land without wasps, that’s a dramatic loss of enjoyment and pleasure.”
Economic cost
Beyond the direct effects on people’s health and wellbeing, wasps are also a drain on the economy, impacting on forestry, farming, bee-keeping, vineyards and more.
A Department of Conservation study, published last year, estimated that wasps cost New Zealand about $130 million a year.