Ecosystems can’t function without the millions of insects that make up the base of the food chain, and a new review in the journal Biological Conservation suggests human activity and climate change are chiseling away at those foundations.
The new study shows 41 percent of insect species have seen steep declines in the past decade, with similar drops forecast for the near future. It’s estimated that 40 percent of the 30 million or so insect species on earth are now threatened with extinction.
Previous studies have looked at smaller areas, with a 2017 study showing 76 percent of flying insects had disappeared from German nature preserves and a study last fall that showed insect populations in pristine rainforest in Puerto Rico have also seen precipitous declines, dropping a factor of 60. This new study, however, looks at 73 studies about insect decline from around the globe. Though most focus on North America and Europe, and it is the first attempt at quantifying the global impact.
Brian Resnick at Vox reports that the individual numbers are sobering. Lepidoptera, the order of insects that includes butterflies, which are often the canary in the coalmine for ecosystem problems, have declined by 53 percent. Orthoptera, which include grasshoppers and crickets, are down about 50 percent, and about 40 percent of bee species are now vulnerable to extinction. Many other orders of insects have seen similar drops.
“We estimate the current proportion of insect species in decline ... to be twice as high as that of vertebrates, and the pace of local species extinction ... eight times higher,” the review states. “It is evident that we are witnessing the largest [insect] extinction event on Earth since the late Permian and Cretaceous periods.”
Marlowe Hood at AFP reports that the impacts on the ecosystem are already being felt. In Europe, over the past 30 years bird populations have declined by 400 million, likely a casualty of the huge decline in flying insects. But birds, lizards, bats and plants aren't the only species that will suffer if insects continue to decline. Hood reports that 75 of the top 115 global food crops depend on insect pollination.
“There are hardly any insects left—that's the number one problem,” Vincent Bretagnolle, an ecologist at French National Centre for Scientific Research says.
The causes are not surprising, and have all been on the radar for decades. Deforestation, agricultural expansion and human sprawl top the list. The wide use of pesticides and fertilizer as well as industrial pollution are also taking massive tolls. Invasive species, pathogens and climate change are also getting punches in.
“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” Matt Shardlow of the U.K. advocacy group Buglife tells Matt McGrath at the BBC. "Allowing the slow eradication of insect life to continue is not a rational option.”
In an editorial, The Guardian points the finger squarely at us:
“The chief driver of this catastrophe is unchecked human greed. For all our individual and even collective cleverness, we behave as a species with as little foresight as a colony of nematode worms that will consume everything it can reach until all is gone and it dies off naturally,” they write. “The challenge of behaving more intelligently than creatures that have no brain at all will not be easy.”
Perhaps counterintuitively, the report states that before the insect apocalypse is complete, some areas may see insects flourish. While climate change is making the tropics much hotter and pushing insects to extinction, warming in more temperate zones are making theses areas more hospitable for certain insect species, including flies, mosquitoes, cockroaches and agricultural pests.
“Fast-breeding pest insects will probably thrive because of the warmer conditions, because many of their natural enemies, which breed more slowly, will disappear,” Dave Goulson from the University of Sussex, not involved in the study, tells the BBC’s McGrath. “It’s quite plausible that we might end up with plagues of small numbers of pest insects, but we will lose all the wonderful ones that we want, like bees and hoverflies and butterflies and dung beetles that do a great job of disposing of animal waste.”
So what can be done to stop the global arthropod apocalypse? The solutions sound familiar for anyone following the various environmental catastrophes unfolding across the globe. Reduce habitat destruction and begin a program of intensive ecological restoration. Face climate change head on. Drastically reduce pesticide use and redesign agricultural systems to make them more insect-friendly.
“Unless we change our ways of producing food,” the authors write, “insects as a whole will go down the path of extinction in a few decades.”