麻豆影视

As a boy in the 1960s, David Wagner would run around his family鈥檚 Missouri farm with a glass jar clutched in his hand, scooping flickering fireflies out of the sky.

鈥淲e could fill it up and put it by our bedside at night,鈥� says Wagner, now an entomologist.

That鈥檚 all gone, the family farm now paved over with new homes and manicured lawns. And Wagner鈥檚 beloved fireflies 鈥� like so many insects worldwide 鈥� have largely vanished in what scientists are calling the global Insect Apocalypse.

As human activities rapidly transform the planet, the global insect population is declining at an unprecedented rate of up to 2% per year. Amid deforestation, pesticide use, artificial light pollution and climate change, these critters are struggling 鈥� along with the crops, flowers and other animals that rely on them to survive.

鈥淚nsects are the food that make all the birds and make all the fish,鈥� said Wagner, who works at the University of Connecticut. 鈥淭hey鈥檙e the fabric tethering together every freshwater and terrestrial ecosystem across the planet.鈥�

TREE OF LIFE

It鈥檚 easy to think insects are doing OK. After all, they鈥檙e nearly everywhere 鈥� crawling through rainforest canopy, burrowing into soil, skimming freshwater ponds or, of course, flitting through the air.

On the biological 鈥渢ree of life鈥� 鈥� which classifies organisms to describe their evolutionary and genetic relationship to one another 鈥� insects fall under the branch, or phylum, called Arthropods, one of the 40 branches of the Animal Kingdom.

In terms of diversity, insects are unrivaled, representing two-thirds of the world鈥檚 more than 1.5 million documented animal species with millions more bugs likely still undiscovered, scientists say. By comparison, there are roughly 73,000 vertebrates, or animals with a backbone from humans to birds and fish 鈥� these represent less than 5% of the known Animal Kingdom, according to the

Their importance to the environment can鈥檛 be understated, scientists say. Insects are crucial to the food web, feeding birds, reptiles and mammals such as bats. For some animals, bugs are simply a treat. Plant-eating orangutans delight in slurping up termites from a teeming hill. Humans, too, see some 2,000 species of insects as food.

But insects are so much more than food. Farmers depend on these critters pollinating crops and churning soil to keep it healthy, among other activities.

• Insects pollinate more than 75% of global crops, a service valued at up to US$577 billion per year, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) says.
• In the United States, insects perform services valued in 2006 at an estimated US$57 billion per year, according to a study in the journal BioScience.
• Dung beetles alone are worth some US$380 million per year to the U.S. cattle industry for their work breaking down manure and churning rangeland soil, the study found.

With fewer insects, 鈥渨e鈥檇 have less food,鈥� said ecologist Dave Goulson at the University of Sussex. 鈥淲e鈥檇 see yields dropping of all of these crops.鈥�

And in nature, about 80% of wild plants rely on insects for pollination. 鈥淚f insects continue to decline,鈥� Goulson said, 鈥渆xpect some pretty dire consequences for ecosystems generally 鈥� and for people.鈥�

DECLINE

Describing a stroll through Costa Rica鈥檚 Area de Conservacion Guanacaste rainforest, evolutionary ecologist Daniel Janzen in 2019 wrote: 鈥淕one are the spiderwebs that decades back entangled those leaves. Gone is the nighttime sparkle in the leaves reflected from thousands of lycosid spider eyes.鈥�

The world has lost 5% to 10% of all insect species in the last 150 years 鈥� or between 250,000 and 500,000 species, according to a February 2020 study in the journal Biological Conservation. Those losses are continuing, though estimates vary due to patchy data as well as uncertainty over how many insects exist.

In the tropics, insects can be 鈥渆xtremely hard to identify, because there are vastly more species than (we) are used to,鈥� Janzen, a University of Pennsylvania professor, told Reuters. 鈥淭here are more species within 100 kilometres of my dwelling in a national park in northwestern Costa Rica than in all of Europe.鈥�

Not knowing exactly what鈥檚 out there makes it harder to detect trouble. suggested the planet is losing about 9% of its land-dwelling insect population each decade. Another January 2021 paper tried to paint a clearer picture by synthesizing more than 80 insect studies and found that insect abundance is declining around 1% to 2% per year. For comparison, the human population is growing at slightly less than 1% per year.

鈥淓ven at the low end of 1% a year, after just 40 years you鈥檙e down more than one-third of species and one-third of individuals 鈥� a third of the entire tree of life lost,鈥� said Wagner, who led the 2021 metastudy, published in the Proceedings of the National Academy of Sciences.

But the reality is likely worse. Wagner鈥檚 team offered an 鈥渋ncredibly conservative鈥� loss estimate, he said, noting that many insect studies are conducted in protected areas such as nature reserves. Degraded farmland or cities would likely reveal far fewer insects.

A WORLD OF DANGERS

The demise of insects can鈥檛 be attributed to any single cause. Populations are facing simultaneous threats, from habitat loss and industrial farming to climate change. Nitrogen overloading from sewage and fertilizers has turned wetlands into dead zones; artificial light is flooding out nighttime skies; and the growth of urban areas has led to concrete sprawl.

鈥淯ntil recently, loss of land was the single greatest driver鈥� of the decline, Wagner said. 鈥淏ut climate change is becoming a far more severe and ominous threat by drying out parts of the planet that were chronically wet. And that is absolutely catastrophic for a lot of insects.鈥�

The introduction of non-native plants, which can dominate new environments, has also hurt insects. Because many insects have evolved to feed on or fertilize a single plant species, the disruption of the plant world can have an outsized effect. For example, the Tegeticula moth species pollinates California鈥檚 famed Joshua trees, while the succulent is the only food source for the moth鈥檚 offspring. If Joshua trees were to disappear, so too could the moth. And vice versa.

WINNERS AND LOSERS

While the situation is bleak for insects at large, a few types of insects are thriving.

鈥淚t鈥檚 generally the pest insects that are thriving because they鈥檙e the ones that breed faster and are favored by human conditions, like all the waste we produce for them to lay their eggs in,鈥� said Sussex鈥檚 Goulson.

Climate change is also giving some nuisance species a boost. Rising temperatures are driving major outbreaks of mountain pine bark beetles, which in two decades have decimated roughly 100,000 square miles (260,000 square kilometres) of North American forest. And with warmer, wetter weather, two disease-spreading mosquitoes Aedes aegypti and Aedes albopictus are expected to expand in Asia, North America and Europe, putting an additional 2.3 billion people at risk from dengue fever by 2080, a June 2019 Nature Microbiology study estimated.

LOSSES BEYOND INSECTS

As insects go, so go their predators.

In North America, nearly all songbirds feed insects to their young. But since 1970, the number of birds in the United States and Canada has fallen by 29%, or roughly 2.9 billion, which scientists theorize is tied to having fewer insects in the world. Some research also has linked insecticide use with declines in barn swallows, house martins, and swifts.

鈥淣ature is just eroding away very slowly,鈥� Wagner said. As insects disappear, 鈥渨e鈥檙e losing the limbs and the twigs of the tree of life. We鈥檙e tearing it apart. And we鈥檙e leaving behind a very simplified and ugly tree.鈥�

(Reporting by Gloria Dickie in London; Graphic by Simon Scarr; Editing by Katy Daigle and Lisa Shumaker)