A jumping spider, which uses sharp eyesight to hunt its prey. ThomasShahan.com/Flickr, CC BY-SA
But a global review of insect research has found another casualty: 40% of insect species are declining and a third are endangered. It confirms what many have been suspecting: in Australia and around the world, arthropods – which include insects, spiders, centipedes and the like — appear to be in trouble.
The global review comes hard on the heels of research published in the Proceedings of the National Academy of Sciences USA that suggests a potent link between intensifying heat waves and stunning declines in the abundance of arthropods.
If that study’s findings are broadly valid – something still far from certain – it has chilling implications for global biodiversity.
Steve Raubenstine / Pixabay
In the mid-1970s, researchers on the Caribbean island of Puerto Rico conducted a large-scale study to measure the total biomass (living mass) of insects and other arthropods in the island’s intact rainforests, using sweep nets and sticky-traps.
Four decades later, another research team returned to the island and repeated the study using identical methods and the same locations. To their surprise, they found that arthropod biomass was just one-eighth to one-sixtieth of that in the 1970s – a shocking collapse overall.
And the carnage didn’t end there. The team found that a bevy of arthropod-eating lizards, birds and frogs had fallen sharply in abundance as well.
In the minds of many ecologists, a widespread collapse of arthropods could be downright apocalyptic. Arthropods pollinate some of our most important food crops and thousands of wild plant species, disperse seeds, recycle nutrients and form key links in food chains that sustain entire webs of life.
This ecological ubiquity arises because arthropods are so abundant and diverse, comprising at least two-thirds of all known species on Earth. In the 1940s, evolutionary biologist J. B. S. Haldane quipped that “God has an inordinate fondness for beetles.” Humans might think we rule the world, but the planet really belongs to arthropods.
Killer heat waves
The researchers who documented the arthropod collapse in Puerto Rico considered a variety of possible causes, including pesticides and habitat disruption. But the evidence kept pointing to another driver: rising temperatures.
Weather stations in Puerto Rico indicate that temperatures there have risen progressively in the past several decades – by 2℃ on average.
But the researchers are far less worried about a gradual increase in temperature than the intensification of heat waves—which have risen markedly in Puerto Rico. This is because nearly all living species have thresholds of temperature tolerance.
For example, research in Australia has shown that at 41℃, flying foxes become badly heat-stressed, struggling to find shade and flapping their wings desperately to stay cool.
But nudge the thermometer up just one more degree, to 42℃, and the bats suddenly die.
In November, heat waves that peaked above 42℃ in north Queensland killed off almost a third of the region’s Spectacled Flying Foxes. The ground beneath bat colonies was littered with tens of thousands of dead animals. Dedicated animal carers could only save a small fraction of the dying bats.
The El Niño connection
El Niño events – fluctuations in Pacific sea-surface temperatures that drive multi-year variations in weather across large swaths of the planet – are also part of this story. New research appears to be resolving longstanding uncertainties about El Niños and global warming.
Recent studies published in Nature and Geophysical Research Letters suggest global warming will in fact intensify El Niños – causing affected areas to suffer even more intensively from droughts and heat waves.
And this ties back to Puerto Rico, because the researchers there believe a series of unusually intense El Niño heatwaves were the cause the arthropod Armageddon. If they’re right then global warming was the gun, but El Niño pulled the trigger.
Beyond heat waves
Puerto Rico is certainly not the only place on Earth that has suffered severe declines in arthropods. Robust studies in Europe, North America, Australia and other locales have revealed big arthropod declines as well.
And while climatic factors have contributed to some of these declines, it’s clear that many other environmental changes, such as habitat disruption, pesticides, introduced pathogens and light pollution, are also taking heavy tolls.
So, at a planetary scale, arthropods are suffering from a wide variety of environmental insults. There’s no single reason why their populations are collapsing.
The bottom line is: we’re changing our world in many different ways at once. And the myriad little creatures that play so many critical roles in the fabric of life are struggling to survive the onslaught.
About The Author
Bill Laurance, Distinguished Research Professor and Australian Laureate, James Cook University
- The Sixth Extinction An Unnatural History
Brand: Kolbert, Elizabeth
WINNER OF THE PULITZER PRIZE
ONE OF THE NEW YORK TIMES BOOK REVIEW'S 10 BEST BOOKS OF THE YEAR
A NEW YORK TIMES BESTSELLER
A NATIONAL BOOK CRITICS CIRCLE AWARD FINALIST
A major book about the future of the world, blending intellectual and natural history and field reporting into a powerful account of the mass extinction unfolding before our eyes
Over the last half-billion years, there have been Five mass extinctions, when the diversity of life on earth suddenly and dramatically contracted. Scientists around the world are currently monitoring the sixth extinction, predicted to be the most devastating extinction event since the asteroid impact that wiped out the dinosaurs. This time around, the cataclysm is us. In prose that is at once frank, entertaining, and deeply informed, New Yorker writer Elizabeth Kolbert tells us why and how human beings have altered life on the planet in a way no species has before. Interweaving research in half a dozen disciplines, descriptions of the fascinating species that have already been lost, and the history of extinction as a concept, Kolbert provides a moving and comprehensive account of the disappearances occurring before our very eyes. She shows that the sixth extinction is likely to be mankind's most lasting legacy, compelling us to rethink the fundamental question of what it means to be human.
The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth's Past Mass Extinctions
Binding: Kindle Edition
Format: Kindle eBook
New York Times Editors' Choice 2017
Forbes Top 10 Best Environment, Climate, and Conservation Book of 2017
As new groundbreaking research suggests that climate change played a major role in the most extreme catastrophes in the planet's history, award-winning science journalist Peter Brannen takes us on a wild ride through the planet's five mass extinctions and, in the process, offers us a glimpse of our increasingly dangerous future
Our world has ended five times: it has been broiled, frozen, poison-gassed, smothered, and pelted by asteroids. In The Ends of the World, Peter Brannen dives into deep time, exploring Earth’s past dead ends, and in the process, offers us a glimpse of our possible future.
Many scientists now believe that the climate shifts of the twenty-first century have analogs in these five extinctions. Using the visible clues these devastations have left behind in the fossil record, The Ends of the World takes us inside “scenes of the crime,” from South Africa to the New York Palisades, to tell the story of each extinction. Brannen examines the fossil record—which is rife with creatures like dragonflies the size of sea gulls and guillotine-mouthed fish—and introduces us to the researchers on the front lines who, using the forensic tools of modern science, are piecing together what really happened at the crime scenes of the Earth’s biggest whodunits.
Part road trip, part history, and part cautionary tale, The Ends of the World takes us on a tour of the ways that our planet has clawed itself back from the grave, and casts our future in a completely new light.
Binding: Kindle Edition
Format: Kindle eBook
The Extinction Cycle: