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‘Half the tree of life’: ecologists’ horror as nature reserves are emptied of insects | Insects | The Guardianhttps://www.theguardian.com/environment/2025/jun/03/climate-species-collapse-ecology-insects-nature-reserves-aoeThe declines witnessed by Janzen – and described by others around the world – are part of what some ecologists call a “new era” of ecological collapse, where rapid extinctions occur in regions that have little direct contact with people.
Reports of falling insect numbers around the world are not new. International reviews have estimated annual losses globally of between 1% and 2.5% of total biomass every year.
“But what we see here in the preserved areas – that as far as we can tell, are free of even these destructive insecticides and pesticides – even here, the insect numbers are going down horrifyingly dramatically,” she says.
Long-term data for insect populations – particularly less charismatic species – is still patchy, but Janzen and Hallwachs join a number of scientists that have recorded huge die-offs of insects in nature reserves around the world.
They include in Germany, where flying insects across 63 insect reserves dropped 75% in less than 30 years; the US, where beetle numbers dropped 83% in 45 years; and Puerto Rico, where insect biomass dropped up to 60-fold since the 1970s. These declines are occurring in ecosystems that are otherwise protected from direct human influence.