Warning of ‘global insect collapse’ as dung beetle numbers fall by more than half

A CLIMATE phenomenon has seen dung beetle numbers fall by more than half, leading to a “devastating global insect collapse”, scientists have said.

Climate change has seen hotter, drier “El Nino events” where a band of warm ocean water developing in the Pacific can cause anything from forest fires to tropical cyclones.

Experts say dung beetles are essential for nature as they spread nutrients and seeds and are an important indicator of the health of the ecosystem.

The team from the UK, Brazil and New Zealand counted more than 14,000 dung beetles from 98 species across 30 forest plots in the Brazilian state of Para, within the Amazon, through several surveys conducted between 2010 and 2017.

They also monitored how much dung was removed and how many seeds were dispersed by dung beetles.

The researchers counted around 8,000 beetles across the plots in 2010. However, in 2016, numbers had plummeted to around 3,700 and, in 2017, they found just 2,600 beetles.

Human disturbance, through activities such as deforestation and predatory logging, significantly increases the flammability of the forests, as forest fires do not occur naturally in the Amazon.

All surveyed forests saw beetle numbers fall, though the results also show forests that burned had fewer beetles than those areas that had just experienced drought.

Lead researcher Dr Felipe França, at Lancaster University, said: “Our investigation provides important insights into how human activities and climate extremes can act together and affect tropical forest biodiversity and ecosystem functioning.

“The loss of these hardworking beetles could indicate a wider problem that many mammals living in the forest may have also succumbed to the drought and fires.

“Dung beetles depend on mammal poo for nesting and feeding.”

Previous research has shown mammal presence has a large influence on dung beetles.

The loss of beetles may indicate other animals were lost, but also raises concerns that forest regeneration will be negatively affected after extreme drought and fire events.

Professor Rodrigo Fadini, from the Federal University of Western Para, said: “We found far fewer dung beetles after the El Nino event, and those that survived were struggling to do their work of spreading nutrients and seeds in forests already impacted either by drought alone or in areas that also experienced fires.”

Professor Jos Barlow, from the Federal University of Lavras, Brazil, and Lancaster University, said: “Tropical forests around the globe are increasingly threatened by anthropogenic climate change, local human disturbances and more frequent and severe weather extremes.

“We need actions to mitigate the continuing climate and biodiversity crisis if we want to keep the forest biodiversity and its contribution to people for future generations.”

The study was published in the journal Biotropica.