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Why scientists are so worried by the huge, sudden loss of insects

A stunning paper on Puerto Rican insects is just one story in an age of mass extinction.

Puerto Rico’s protected rainforests are losing insects — fast.
Wolfgang Kaehler/LightRocket/Getty Images
Brian Resnick is Vox’s science and health editor, and is the co-creator of Unexplainable, Vox's podcast about unanswered questions in science. Previously, Brian was a reporter at Vox and at National Journal.

In Puerto Rico’s rainforest, scientists have observed an astounding loss of life at the very base of the food web. It’s the insects.

As an alarming new study in Proceedings of the National Academy of Sciences outlines, between 1976 and 2013, the number of invertebrates (like insects, spiders, and centipedes) in the Luquillo rainforest caught in survey nets plummeted by a factor of four or eight. When measured by the number caught in sticky traps, invertebrates declined by a factor of 60. These dramatic drops occurred despite the fact that the forest is a protected wildlife area.

The researchers note that this loss of invertebrates — which serve as food for many other forms of life in the ecosystem — has also coincided with losses of birds, lizards, and frogs. “The food web appears to have been obliterated from the bottom,” the Washington Post’s Ben Guarino reported on the study. Guarino’s story quotes one invertebrate expert who called the research “hyper alarming.”

The report is just one example of a larger, troubling trend: Insects — including yes, bees — and other critters are rapidly disappearing around the world. A 2017 study in Germany noted a 75 percent decline in flying insects over three decades. “The widespread insect biomass decline is alarming,” the authors wrote, “ever more so as all traps were placed in protected areas that are meant to preserve ecosystem functions and biodiversity.”

There’s no one reason why so many critters are dying, and researchers are still unclear on what’s driving the change. Climate change (and changing drought and weather conditions) is strongly implicated. And it’s also partly due to environmental toxins and possibly pesticides. But it’s fair to say they’re mainly dying because humans are changing the world for the worse.

Humans are driving a huge array of species to extinction

Two monkeys in the snow
A baby monkey is cuddled by its mother to keep warm as the sub-zero temperatures freeze life during a fresh snowfall in Tangmarg.
Tauseef Mustafa/AFP/Getty Images

The world is losing biodiversity, fast. If you take stock of all the studies that point to the fact we’re living in an age of mass extinction, perhaps even the sixth mass extinction, it can all feel overwhelming.

Mammals, the branch of the animal kingdom to which we belong, are also in peril, another study, also published in PNAS this week, illustrates. More than 300 mammal species have been wiped out since humans overran the world after the last ice age (and an additional 25 percent of all mammals alive today are threatened with extinction). The study asks a simple question: How many years would it take for evolution to naturally replace all the species that have died as a result of humans?

Their answer: 3-7 million years. Science writer Ed Yong points out “that’s at least 10 times as long as we have even existed as a species.”

It’s important to take stock of what we lose when we lose species. A 2017 report in Science Advances found that around 60 percent of primate species are threatened with extinction — all due to human activity.

The report found every member of the primate family Hominidae (great apes, which includes gorillas and chimpanzees) is endangered or critically threatened (except for us). Around 87 percent of Indriidae (larger lemurs) are similarly endangered or threatened.

Think of what that means: Primates are our closest relatives on Earth. If we can understand them better, we can understand ourselves. Here’s how Carl Zimmer at the New York Times explains it:

The first primates evolved roughly 80 million years ago, and then split into the living lineages over millions of years. By comparing our biology to those of other primates, we have learned about the evolution of our brains, our vision and our vulnerability to diseases.

But don’t necessarily consider primate losses to be more important, or painful, than insect losses. Insects and other arthropods form a hugely important foundation in many ecosystem animal food webs. They also are the world’s pollinators, ensuring that plants produce new seeds and new generations. Without the foundation of insects, the ecosystem collapses.

We need to take stock of the wildlife we’ve lost

Here’s one more sobering example of just how many species around the world are threatened.

The past few decades have seen a massive die-off of amphibians, which scientists fear are some of the most vulnerable animals to losses in a rapidly changing world. That may be because amphibians need both healthy aquatic and terrestrial environments to thrive. Change just one enough, and species suffer.

In 2010, a survey of 25,780 species of vertebrates found that 41 percent of the amphibians were threatened with extinction. “On a per-species basis, amphibians are in an especially dire situation, suffering the double jeopardy of exceptionally high levels of threat coupled with low levels of conservation effort,” the study noted. Since just 1970, 200 species of frog have perished.

Earlier this year, researchers, tried to estimate a weight for all of life on Earth. It was a fun exercise, putting humanity’s relative small weight on Earth in dramatic contrast to the weight of all the other forms of life. There are an estimated 550 gigatons of carbon of life in the world. And we all weigh just .06 gigatons.

If everyone on the planet were to step on one side of a giant balance scale, and all the bacteria on Earth were to be placed on the other side, we’d shoot violently upward. That’s because all the bacteria on Earth combined are about 1,166 times more massive than all the humans.

We’re a small part of the living world, but yet, we make such an outsized impact on it.

The authors of the weight estimate were also sure to calculate what was missing from their figures. They estimated that the mass of wild land mammals is seven times lower than it was before humans arrived. Similarly, marine mammals, including whales, are a fifth of the weight they used to be because we’ve hunted so many to near extinction.

Although plants are still the dominant form of life on Earth, the scientists suspect there used to be approximately twice as many of them — before humanity started clearing forests to make way for agriculture and our civilization. Animals are going extinct 1,000 to 10,000 faster than you’d expect if no humans lived on Earth.

Insects dying off in Puerto Rico may seem like a small — but shocking — story. What’s all the more alarming is that stories like it are happening everywhere.

With so much devastating and widespread loss, it’s hard to say where we should focus our attention — other than just working to stem the progression of climate change. In Science, Jonathan Baillie, the chief scientist at the National Geographic Society, and Ya-Ping Zhang, the vice president of the Chinese Academy of Sciences, argued that half of all land should be protected for wildlife by 2050, to give plants and animals a chance to thrive.

This is a lofty, perhaps unrealistic goal. But we’ve taken so much from wildlife. We need to think more about how to stop taking environments away from plants and animals. “Simply put,” they write in Science, “there is finite space and energy on the planet, and we must decide how much of it we’re willing to share.”

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