Climate change is killing off Earth's little creatures

February 12, 2019 by Bill Laurance, The Conversation
A jumping spider, which uses sharp eyesight to hunt its prey. Credit: ThomasShahan.com/Flickr, CC BY-SA

Climate change gets blamed for a lot of things these days: inundating small islands, fueling catastrophic fires, amping-up hurricanes and smashing Arctic sea ice.

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.

Arthropod Armageddon

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 biomass was just one-eighth to one-sixtieth of that in the 1970s – a shocking collapse overall.

Our natural world depends on arthropods. Credit: Steve Raubenstine/Pixabay

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.

Insects are crucial in food webs for species such as this hummingbird. Credit: Pixabay

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.

Bats die en-masse during a recent heatwave.
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 .

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.

Monarch butterflies are declining in the USA and Mexico, probably from habitat disruption. Credit: Pixabay
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.

Explore further: Two degrees decimated Puerto Rico's insect populations

Related Stories

Two degrees decimated Puerto Rico's insect populations

October 15, 2018

While temperatures in the tropical forests of northeastern Puerto Rico have climbed two degrees Celsius since the mid-1970s, the biomass of arthropods—invertebrate animals such as insects, millipedes, and sowbugs—has ...

Landslides triggered by Hurricane Maria

February 7, 2019

Hurricane Maria hit the island of Puerto Rico on 20 September 2017 and triggered more than 40,000 landslides in at least three-fourths of Puerto Rico's 78 municipalities. In a new article from GSA Today, authors Erin Bessette-Kirton ...

World seeing 'catastrophic collapse' of insects: study

February 11, 2019

Nearly half of all insect species worldwide are in rapid decline and a third could disappear altogether, according to a study warning of dire consequences for crop pollination and natural food chains.

Urban insects are more resilient in extreme weather

January 11, 2018

A study led by Amy Savage, a Rutgers University-Camden assistant professor of biology, will help researchers understand how to make predictions and conservation decisions about how organisms living in cities will respond ...

Recommended for you

Archaeologists discover Incan tomb in Peru

February 16, 2019

Peruvian archaeologists discovered an Incan tomb in the north of the country where an elite member of the pre-Columbian empire was buried, one of the investigators announced Friday.

Where is the universe hiding its missing mass?

February 15, 2019

Astronomers have spent decades looking for something that sounds like it would be hard to miss: about a third of the "normal" matter in the Universe. New results from NASA's Chandra X-ray Observatory may have helped them ...

What rising seas mean for local economies

February 15, 2019

Impacts from climate change are not always easy to see. But for many local businesses in coastal communities across the United States, the evidence is right outside their doors—or in their parking lots.

The friendly extortioner takes it all

February 15, 2019

Cooperating with other people makes many things easier. However, competition is also a characteristic aspect of our society. In their struggle for contracts and positions, people have to be more successful than their competitors ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.