Joe Bonfield re-entered his homely kitchen, honey in hand, just as the kettle boiled. I was meeting Bonfield, a graduate of UCD, at his home in the foothills of the Wicklow Mountains. He completed a BSc in Physics with Astronomy & Space Science and an MSc in Space Science & Technology. In his spare time, he is a beekeeper.

I closely examined the deep yellow honey he had just harvested from his hive while quizzing him about the practicalities of caring for bees. The conversation quickly turned to the reasons behind the declining bee populations in Ireland. “Honey bees are at a loss because of the varroa mite. The parasite carries diseases like the deformed wing virus and that can lead to colony collapse disorder,” he said. “But the warmer winter last year caused havoc, because the bees were active and using energy when they should’ve been idle in the hive.”

“There are definitely less bees around. Even bumblebees are getting scarce,” Bonfield stated. The problem of declining bee populations is not unique Ireland. The rusty-patched bumblebee, native to North America, declined by 87% in the last 20 years. Nor is the problem unique to bees.

The data confirmed his intuition: in three and a half decades, 98% of ground insects and 80% of insects in the tree canopy had disappeared

Brad Lister and Andres Garcia published a study last October, the results of which were labeled as “hyper-alarming” by an expert in invertebrate conservation. Lister had visited a rainforest in Puerto Rico in 1976 and, after returning 35 years later, he was surprised to see a dramatic decline in insect populations.

“One of the things I noticed in the forest was a lack of butterflies. They used to be all along the roadside, especially after the rain stopped, hundreds upon hundreds of them. But we couldn’t see one butterfly,” Lister said, speaking to The Guardian. The data confirmed his intuition: in three and a half decades, 98% of ground insects and 80% of insects in the tree canopy had disappeared. Lister and Garcia also discovered that insect numbers in a forest in Mexico dropped by 80% since the 1980s. In Germany, 7,000 km away, the number of flying insects has dropped by 75% in 25 years. In yet another study, scientists found the population of monarch butterflies in the United States has plummeted by 90% in 20 years.

Insects play a key role in the food chain, and what results when insect populations are decimated clear. Lister saw a contemporaneous decline in birds and frogs that feed on insects by 50–65%. In an Australian eucalyptus forest, severe heat eradicated the insect population and, consequently, nearly all birds. Aside from being a food source, insects are also critical for pollination, breaking down matter and aerating the soil. Such is the vital role insects play in the ecosystem, their disappearance has been described as “ecological Armageddon” in many headlines around the globe.

The issue of population decline extends beyond insects. Prof. Ron Milo published a study in 2018 which found that whether it be for development, farming, or logging, human-caused habitat destruction is to blame for the loss of 50% of plants and 83% of wild animals. Combined with modern farming practices, this has lead to a strange situation, where now 60% of all mammals on Earth are livestock. Humans make up 36%, and wild animals constitute just 4%. Similarly, farmed poultry makes up 70% of all birds on the planet. “When I do a puzzle with my daughters,” said Milo, “there is usually an elephant next to a giraffe next to a rhino. If I was trying to give them a more realistic sense of the world, it would be a cow next to a cow next to a cow and then a chicken.”

While pesticides and habitat destruction contribute to insect collapse across the world, the Puerto Rican forest that Lister visited is a protected area. Lister concludes that the collapse of the rainforest ecosystem is being driven by climate change. Scientists had predicted that because tropical insects evolved in an exceptionally stable climate, they would be more susceptible to warming conditions. In the past 30 years, average temperatures in the forest have risen 2.0°C, and there have been more instances of extreme heat. In recent years, 44% of days exceeded 29°C, whereas in the 1970s, no days exceeded this temperature.

There are practical steps that can be taken to stem this decline. Many scientists have called for the preservation and restoration of forests and wetlands. Agricultural practices that stimulate biodiversity, such as planting wildflowers around monocrops, and a more prudent use of pesticides would also be beneficial.

The decline of insects doesn’t pack the same emotional punch as the decline of pandas. But they represent a vital cog in the ecosystem

Globally, little is known about the scale of the situation. Lister’s study is only a glimpse into the issue, and he fears that the impact of climate change on tropical ecosystems is far greater than currently estimated. More research in a variety of different habitats is required, but that is only half the problem, as there are just a handful of studies that have tracked insect numbers in the past. This makes it challenging to establish the long-term trends.

Insect numbers are difficult to track and the feeling that their numbers are declining in many places is just that – a feeling. There seems to be less insects under rocks, in gardens, or on windscreens than there used to be. For many, this may be as tangible as the plummeting insect population feels, and people would be forgiven for failing to see the downside of the situation. The decline of insects doesn’t pack the same emotional punch as the decline of pandas. But they represent a vital cog in the ecosystem and, according to Prof. Dave Goulson, “if we lose the insects, then everything is going to collapse.”