Beekeeper Roger Garrison holds a container with a queen bee on the rooftop of a San Francisco hotel, April 18, 2016. AP Photo/Eric Risberg

Of the world's 1 million known insect species, 400,000 are in decline, according to a new report..

Since 1970, 50% of all insects may have disappeared.

The die-offs are happening because farmers are using more pesticides to protect crops. Insects are also losing their habitats to farming and urbanization.

Three-quarters of the world's crops are pollinated by insects, so extinctions could have a major impact on food production.

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Insects are disappearing en masse.

A new report from the Somerset Wildlife Trust in the UK found that 41% of the world's 1 million known insect species are threatened with extinction.

The decline of butterflies, bees, and other bugs might seem low on a list of environmental concerns that includes rising seas and melting glaciers.

Yet the loss of these species could be devastating.

Insects are food sources for countless bird, fish, and mammal species. They recycle nutrients in the soil, and break down dead carcasses and animal waste. Pollinators like bees and hoverflies also perform a crucial role in fruit, vegetable, and nut production.

But insects are quickly losing their habitats to farmland and urbanization, and are threatened by farmers' use of pesticides as well.

A monarch butterfly clings to a plant at the Monarch Grove Sanctuary in Pacific Grove, California, December 30, 2014. Michael Fiala/Reuters

"We can't be sure, but in terms of numbers, we may have lost 50% or more of our insects since 1970 - it could be much more," ecologist Dave Goulson, the author of the new report, wrote. "We just don't know, which is scary ... Perhaps more frightening, most of us have not noticed that anything has changed."

'A catastrophic collapse of Earth's ecosystems'

According to Goulson's report, "it is hard to avoid the conclusion that there has been a major decline in insect biomass."

Goulson, a professor of biology at the University of Sussex, found that in the UK specifically, 23 bee and wasp species have gone extinct in the last century. Butterfly species have declined by as much as 77% since the mid-1970s, and populations of local insect-eating birds, like the spotted flycatcher, have similarly shrunk.

His work relied heavily on a February 2019 study in which scientists Francisco Sánchez-Bayo and Kris Wyckhuys looked at 73 historical reports on insect declines around the world. Their results showed that the total mass of all insects on the planet is decreasing by 2.5% per year.

Beyond the 41% of the world's known insect species that are already in decline, Sánchez-Bayo and Wyckhuys noted that 31% are threatened (according to criteria set by the International Union for Conservation of Nature), and 10% are going locally extinct.

The February study also suggested that moths and butterflies are disappearing; between 2000 and 2009, the UK lost 58% of butterfly species on farmed land.

Dragonflies, mayflies, and beetles appear to be dying off as well.

A pink-legged tiger moth. Flickr/Jen Forman Orth

If this trend continues unabated, Sánchez-Bayo and Wyckhuys warned, the Earth may not have any insects at all by 2119.

Already, insects' extinction rate is eight times faster than that of mammals, birds, and reptiles. That biodiversity crisis could trigger a "catastrophic collapse of Earth's ecosystems," the authors said.

Gary Mantle, chief executive of the Wiltshire Wildlife Trust (another environmental group in the UK), told The Guardian that "this unnoticed apocalypse should set alarms ringing."

Disappearing bees

One of the most concerning trends in this insect apocalypse is the decline of honey bees.

In the US, the number of honey-bee colonies dropped from 6 million in 1947 to just 2.5 million in 2014.

Between October 2018 and April 2019, about 40% of US honey bee colonies died, according to research from the University of Maryland. That's the highest winter bee loss in 13 years.

Researchers have observed a similar problem in the UK: one-third of 353 wild bee and hoverfly species there experienced declines between 1980 and 2013, according to a March study.

Honey bees pollinate $15 billion worth of US food crops, according to the Associated Press. One-third of everything Americans eat comes from pollinators like honey bees, per US Department of Agriculture estimates.

Worldwide, approximately three-quarters of all crops are pollinated by insects, Goulson said. So insect extinctions could have a major impact on our food production and supply.

Experts think honey bees are dying due to a combination of decreasing crop diversity, poor beekeeping practices, and loss of habitat. Pesticides like neonicotinoids can also kill bees in droves, causing colony collapses.

Goulson reported that 75% of honey samples from around the world contained neonicotinoids.

A laborer sprays pesticides on genetically modified cotton crops in Guntur, Andhra Pradesh, India, October 17, 2017. Mayank Bhardwaj/Reuters

He added that in the UK, the number of pesticide applications has doubled over the last 25 years, and that's primarily to blame for widespread insect declines there.

To make the problem worse, insect habitats are disappearing as more land area gets used for farmland and urban development around the world.

'We can't wait another 25 years before we do anything because it will be too late'

Studying changes in insect populations over time is challenging, and many analyses rely heavily on reports about bugs in Europe and North America, even though most insects live in the tropics. Because of this, some scientists have pushed back against the idea that all insects could disappear within a century.

"I understand the desire to put numbers to these things to facilitate the conversation, but I would say all of those are built on mountains of unknown facts," Michelle Trautwein, an entomologist from the California Academy of Sciences, told The Atlantic's Ed Yong in February.

But the data trends we do have are troubling.

A 2017 study concluded that populations of flying insects in Germany had decreased by more than 75% percent in the last three decades. Another study conducted in Puerto Rico found that 98% of the island's ground insects had vanished since the 1970s.

"The overwhelming weight of evidence that exists suggests the rapid decline is a real phenomenon," Goulson told The Guardian.

Although he agrees that there is a shortage of data on insect population trends, he added: "It really worries me to hear people say we need more long-term studies to be sure. That would be great, but we can't wait another 25 years before we do anything because it will be too late."

Trautwein agreed that it's better to approach the risk of insect extinctions with caution, rather than disregard.

"I don't see real danger in overstating the possible severity of insect decline, but there is real danger in underestimating how bad things really are," she told the Atlantic.

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