A new point in history has been reached, entomologists say, as climate-led species’ collapse moves up the food chain even in supposedly protected regions free of pesticides

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.

Widespread use of pesticides and fertilisers, light and chemical pollution, loss of habitat and the growth of industrial agriculture have all carved into their numbers. Often, these were deaths of proximity: insects are sensitive creatures, and any nearby source of pollution can send their populations crumbling.

But what Janzen and Hallwachs are witnessing is a part of a newer phenomenon: the catastrophic collapse of insect populations in supposedly protected regions of forest. “In the parts of Costa Rica that are heavily hit by pesticides, the insects are completely wiped out,” Hallwachs says.