Bogong moths rebound across eastern Australia after 2017 crash
Citizen science sightings show a spring surge in bogong moths, a species described as undetectable in alpine regions after a dramatic 2017 crash.
At a glance
- Citizen science sightings show bogong moths surging across eastern Australia this spring after years of decline.
- The moths once numbered in the billions, with up to 4 billion migrating to the Australian Alps each summer, but crashed in 2017.
- Ecologist Ken Green has linked the crash mainly to Australia's 2017-2019 drought, with pesticides and light pollution behind a slower decline.
Bogong moths have returned in large numbers across eastern Australia this spring, with citizen science sightings showing a sharp recovery for a species that was described as "undetectable" in the alpine regions after a population crash in 2017.
Ecologist-led surveys for this year are not yet available for comparison with previous years, but observations logged by volunteers on the citizen science platform iNaturalist through the Bogong Watch project show the moth population has exploded. Each dot on the project's animated map represents a sighting, which may include one or more moths.
Researchers caution that citizen science data has limitations: observation numbers over time can be skewed by differences in effort and participation, for example. Even so, the trend is clear.
From billions to undetectable
Bogong moths were once so common that researchers put their numbers in the billions, with as many as 4 billion migrating to the Australian Alps in summer to aestivate in cool caves. The moths famously caused panic at the Sydney Olympics closing ceremony in 2000, and were known to invade Parliament House in Canberra each year.
Their numbers declined slowly between 1980 and 2016 before crashing dramatically in the summer of 2017, when the population fell so low that the species was described as undetectable in the alpine regions.
Ken Green, an ecologist who has monitored bogong moths for more than 40 years, has previously told the Guardian that Australia's drought through 2017, 2018 and 2019 was probably the largest contributor to the crash, with pesticides and urban light pollution contributing to the slower decline from the 1980s.
Why the recovery matters
The spring surge is good news for the plants the moths pollinate and for the endangered species that rely on them for food, including the mountain pygmy possum.
Source: The Guardian.
Questions and answers
- Why did bogong moth numbers crash?
- Ecologist Ken Green has said Australia's drought through 2017, 2018 and 2019 was probably the largest contributor. Pesticides and urban light pollution contributed to a slower decline from the 1980s, and the population crashed dramatically in the summer of 2017.
- How many bogong moths were there before the decline?
- Researchers say the moths once numbered in the billions, with as many as 4 billion migrating to the Australian Alps in summer to aestivate in cool caves. Numbers declined slowly between 1980 and 2016 before the 2017 crash.
- Why do bogong moths matter?
- They pollinate plants and are food for endangered species including the mountain pygmy possum. Their surge across eastern Australia this spring is described as good news for the species that depend on them.
