Since 2009, a dedicated member of the Moths and Butterflies of New Zealand Trust has been conducting weekly walks along the same route from October to March to document butterfly populations.
The collected data culminated in a report attributing the decline primarily to common and paper wasps.
“Environmental pressures, particularly from introduced pest wasps (Vespula and Polistes spp.), are the most likely culprits,” stated Jacqui Knight, a founding trustee.
Knight noted that a wasp survey conducted in 2025 indicated these pests were not only harming native insects like wētā and young birds but also “restricting people’s ability to work and enjoy outdoor activities.”
“We worry about the decline of other species too, but the absence of monarchs, which are larger and once adorned our gardens every summer, is especially noticeable,” she remarked.
She is urging the government to take these impacts more seriously and is calling for volunteers to engage in butterfly transect monitoring.
“There are additional factors affecting our native wildlife that require attention. Our efforts are just beginning,” Knight emphasized.
