A recent global decline in insect numbers could mean a surge in certain pests. According to a recent study published in the journal Biological Conservation, up to 40% of insect species including bees, ants, and beetles have seen dramatic rates of decline around the world. This could mean a boom in pests such as houseflies and cockroaches.
Researchers say insects have been disappearing eight times faster than reptiles, birds, and mammals. Intensive agriculture, climate change, and pesticides are the main causes.
“The main factor is the loss of habitat, due to agricultural practices, urbanization, and deforestation,” said Dr. Francisco Sanchez-Bayo from the University of Sydney, the lead author of the study.
“Second is the increasing use of fertilizers and pesticides in agriculture worldwide and contamination with chemical pollutants of all kinds,” said Sanchez-Bayo. “Thirdly, we have biological factors such as invasive species and pathogens; and fourthly, we have climate change, particularly in tropical areas where it is known to have a big impact.”
Insects make up a major part of the world’s ecosystem. They provide food for birds such as the Canada goose, whose numbers have increased in the last 50 years. They also provide food for small mammals like bats.
But insects are more than just food. They also pollinate 75% of the world’s crops and replenish soils, including all 60 different types in Texas, to keep pest numbers in check.
Previous studies have shown that individual species of insects such as bees have seen major declines in developed economies, but Sanchez-Bayo’s study takes a broader look.
Researchers reviewed 73 studies that have been conducted in the last 13 years. They found that one-third of insect species are classified as endangered and that current declines could lead to the extinction of 40% of insects in the next few decades.
“It’s not just about bees, or even about pollination and feeding ourselves,” said Matthew Shardlow from Buglife, a UK conservation trust, “the declines also include dung beetles that recycle waste and insects like dragonflies that start life in rivers and ponds.”
Germany has seen a rapid decline of flying insects in recent years. Puerto Rico has also seen a drop in flying insects in its forests. The reason for both, experts say, is rising global temperatures. So while a 119% increase in hardwood trees in American forest seems great, it’s not enough to stem the tide of climate change around the world.
“It is becoming increasingly obvious our planet’s ecology is breaking and there is a need for an intense and global effort to halt and reverse these dreadful trends,” said Shardlow. “Allowing the slow eradication of insect life to continue is not a rational option.”
The decline in insect species could have a significant effect on the food chain. Many species of birds, reptiles, and fish rely on insects as their main food source. Without them, species higher up on the food chain could also be wiped out.
But while some species of animals will be threatened by the decline in insects, others will thrive. Dr. Dave Goulson from the University of Sussex says fast-breeding pest insects could thrive in the warming conditions. “[And] many of their natural enemies, which breed more slowly, will disappear,” said Goulson.
Tough, adaptable species such as houseflies, cockroaches, and rats can comfortably live in human-made environments. For instance, the top three rat-filled cities in America include Chicago, New York City, and Washington, D.C.
Still, while this news is alarming, experts say people can still do their part to make the world safer for insects such as making their gardens insect-friendly and not using pesticides.