Bogong moths are back. After a population crash so severe the species was described as "undetectable" in alpine regions, citizen science data from the iNaturalist Bogong Watch project shows observations exploding across eastern Australia in 2025. The visual evidence is striking: animated maps of sightings show a continent that went dark after 2017 now lit up again. The backstory is a textbook ecological collapse. Bogong populations once numbered as many as 4 billion moths migrating annually to aestivation caves in the Australian Alps. These were the moths that famously swarmed the Sydney Olympics closing ceremony in 2000 and invaded Parliament House in Canberra every year. Between 1980 and 2016 the population declined slowly, driven by pesticides and urban light pollution, then fell off a cliff during Australia's 2017-2019 drought. Ecologist Ken Green, who has monitored bogongs for more than 40 years, identified drought as the primary driver of the crash, with pesticides and light pollution as slower-burning contributors. The distinction matters: drought is cyclical, while pesticide and light pollution pressures are structural. A recovery during wetter conditions is consistent with the drought hypothesis but does not resolve the structural threats. The rebound carries real ecological weight. Bogong moths are a keystone species in the alpine food web, pollinating plants and serving as a critical food source for the endangered mountain pygmy possum. Years of moth absence meant years of cascading stress on dependent species. A strong moth season reverses that pressure — but one season does not constitute recovery. The data itself deserves scrutiny. Citizen science platforms like iNaturalist generate observation counts that reflect both actual population change and changes in observer effort and participation. The Guardian acknowledges this caveat. Formal ecologist-led survey figures are not yet available for comparison. The signal is real — too many people across too wide an area are reporting moths for this to be an artifact — but precise population estimates will require professional monitoring data. What makes this story structurally interesting is the speed of the rebound. Insect populations can recover faster than vertebrate populations when conditions improve, because reproductive cycles are short and generation times are measured in months, not years. The bogong recovery, if confirmed by formal surveys, would be a case study in insect population elasticity — the capacity of a species to snap back from near-zero when the primary stressor (drought) lifts. The twenty-year question is whether the structural pressures — pesticide use, expanding urban light pollution, and increasing drought frequency under climate change — will allow the recovery to hold, or whether this is a temporary reprieve between crashes. One good season is not resilience. Sustained monitoring will determine whether Australia's alpine ecosystems have a keystone species or a recurring crisis.
