Where have all the insects gone?
- Randi Pokladnik
- March 5, 2020
- 2338
A recent study conducted in Germany and published in the peer-reviewed journal, Plos One, showed the abundance of flying insects has plunged by three-quarters over the past 25 years.
This study, started in 1989, enlisted the help of amateur entomologists who collected and catalogued insect species from 63 different nature reserves in Germany.
This loss equates to an average of approximately 5 percent of flying insects disappearing each year. Species lost include many valuable pollinators such as flies, moths, butterflies and bees, all of which pollinate flowers and crops.
It also includes species that provide food for many animals such as birds, bats, some mammals, fish, reptiles and amphibians. Additionally flies, beetles and wasps are predators and decomposers, controlling pests and cleaning up the ecosystems.
Many of us are already noticing the decline of insects. Dave Goulson of Sussex University UK has made this observation. The lack of bugs killed by our car windscreens “suggests a major decline with people remembering many more bugs squashed on their windscreens in the past.”
I’ve noticed this “lack of squashed insects” too. I live in the woods and seldom see bug bodies from bugs colliding with my windshield. A little over 20 years ago, we took frequent road trips to Nebraska to see my husband’s family in Omaha.
We often drove straight through the night during warm summer months. The sides of the roads along cornfields were lit up like mini fireworks displays, courtesy of millions of lightening bugs.
Last year we drove back to Nebraska for a family reunion. It was noticeably different as far as the number of lightening bugs we encountered. We saw only a few.
Sarah Fowler, an evolutionary geneticist and assistant biology professor at Bucknell University in Pennsylvania, is studying the lightening bug family, Lampyridae, to see what is causing their declines.
In a recent report she said this family has been around for over 100 million years. We can find them all over the world as they split into two groups early on. One group populated the Americas, where we refer to them as lightening bugs or fireflies, and the other group is found in Europe and Asia, where they are known as glowworms.
Lightening bugs are beetles with over 2,000 different species. In 2018 the International Union for Conservation of Nature created the “firefly specialist group” to study these beetles. By the end of 2020, they hope to publish a report detailing the threats to these beetles.
Some early results from their research show possible threats include loss of habitat, light pollution, pesticides and lack of food sources. If we turn off lights, stop using pesticides on our lawns and around our homes, and work to preserve habitats, we can help curtail the decline in populations.
In addition to insect species being affected by habitat loss, scientists are noting major losses of insect populations due to climate change. A recent study in the journal, Science, showed if the average global temperature is increased by 3.2 degrees centigrade above pre-Industrial Revolution temperatures, 49 percent of all insect species would lose half of their exiting habitat ranges.
What is especially troubling is the three major groups of insects responsible for pollination are particularly sensitive to warming. “Global average surface temperatures in the past 2 million years have rarely approached the levels projected over the next few decades,” said Guy Midgley of the University of Stellenbosch, South Africa.
Another study published in Nature Communications enlisted the help of both moth and butterfly enthusiasts to gather data for 130 species in England over a 20-year period from 1995-2014.
Measurements showed that during this time period the average spring temperatures had increased by 0.5 degrees centigrade and the time period for the emergence of species from chrysalis and cocoons was from three to seven days sooner.
For some more flexible butterfly species like the small blue, England’s tiniest butterfly, this means more time to allow for another generation of butterflies to be produced. However, for other less flexible species, an earlier emergence was of no benefit. This was true for the high brown fritillary, deemed England’s most endangered butterfly.
The fritillary is a single-generation butterfly whose caterpillars only feed on woodland violets. According to Butterfly Conservation, a group of butterfly enthusiasts in England, around two-thirds of butterfly species have declined in the UK over the past 40 years. If this trend continues, it might have unpredictable knock-on effects for other species in the ecosystem.
A study of moths in Borneo published in The Science Times showed moths were adapting to increases in temperature and deforestation by becoming smaller in size. While this might help reduce the amount of food needed, it also will mean species that depend on moths as a food source will need more moths of the smaller size. It might also mean less eggs will be produced from moths.
The 7,000 members of the Entomological Society of America agree insect populations are declining and this will soon affect all of us, as well as future generations. Some of the results of declining populations are increasing food insecurity from crop losses.
It is estimated $210 billion of global crops are pollinated by insects. The ESA said managed honey bee populations contribute $17 million of economic value to seed and crop production in the U.S. alone. Wild bees contribute billions of dollars’ worth of pollination services. Ask yourself how often do you see honey bees today?
According to the journal, Biological Conservation, Oklahoma has only half the number of bumblebee species it had in 1949. The study also showed the number of honeybee colonies had dropped from 6 million in the U.S. in 1947 to 2.5 million today. The loss of bees is due to colony collapse, parasites, neonicotinoid pesticides and climate change.
“If insect species losses cannot be halted, this will have catastrophic consequences for both the planet’s ecosystems and for the survival of mankind,” said Francisco Sánchez-Bayo, at the University of Sydney, Australia.