A global look at a deepening crisis

The heart of the problem

In some ways, the heated debate over this particular mega-survey is academic and arguably a distraction. Whether insects may be vanishing at a rate of 1 percent or 2.5 percent annually, or somewhere in the middle, it’s still catastrophically too much. Even as some scientists question the review’s direst conclusions, none said we shouldn’t be concerned, sitting back and doing nothing.

Here’s the crux of the matter: when asked how they would rate the insect abundance crisis on a scale of 0 to 10 — 10 being direst — the answers Mongabay received from researchers on six continents ranged from 8 to, yes, 10.

Still, not everyone is utterly convinced of the drastic insect decline narrative. Manu Saunders, an entomologist and ecologist doing postdoctoral studies at the University of New England in Australia, isn’t ready to put a number on the crisis or describe it as “global,” saying we just don’t know enough yet. “There is no verified evidence that global insect populations are in decline, based on the collective scientific knowledge of insect ecology generally and insect population studies.” Saunders says that, at this point, she’s less concerned about insect decline than about our “limited understanding of what these changes mean, because we know so little about most insect species.”

That being said, all but one of the scientists interviewed for this story believe that, limited as it is, current research suggests something, or more than one thing, is decimating insects, potentially across most insect families and potentially around the world. A paper in Science in 2014, looking at declines across all animal species, concluded that invertebrate populations, which include insects, had fallen by 45 percent over 40 years. This is less than the 2.5 percent annual drop listed in the meta-review, but still staggering and shocking.

“Estimates alone do not tell us the entire story. They are like movie trailers — you get the gist but you have to watch the entire movie to understand what is going on,” says Danielle Salcido, a University of Nevada graduate student who is studying neotropical insects. Put simply, while global estimates are informative, they don’t give us the specifics of which species’ populations are falling, rising or stable; in other words, the meta-research just can’t capture the full complexity of nature.

Why we can’t wait

Given the dearth of data on insect families (there has been, for example, almost no research into the abundance of ants), much of today’s unfolding crisis remains shrouded in mystery. But this is what we do know: something may be seriously, perhaps catastrophically, amiss in the largely unseen world inhabited by insects. And that’s enough, entomologists say, for us to act now.

“I think getting caught in the debate over how legit these studies are, how serious the situation is, is potentially just wasting important time,” Trautwein says.

“There’s no harm done in taking these studies seriously, and assuming we’re at a point where we’ve been warned that we need to be a lot more careful and contemplative about how to move forward.”

For Martins, whose Kenyan bush meals are lonelier now, the concern isn’t so much for the lack of his little uninvited guests, but for humanity.

“To a large extent, we’re still living in the age of insects,” he says. “If we continue messing things up, the insects will have the last laugh.”

Citations:

Dirzo, R., Young, H. S., Galetti, M., Ceballos, G., Isaac, N. J., & Collen, B. (2014). Defaunation in the Anthropocene. Science, 345(6195), 401-406. doi:10.1126/science.1251817

Sánchez-Bayo, F., & Wyckhuys, K. A. G. (2019). Worldwide decline of the entomofauna: A review of its drivers. Biological Conservation, 232, 8-27). doi:j.biocon.2019.01.020

Hallmann, C. A., Sorg, M., Jongejans, E., Siepel, H., Hofland, N., Schwan, H., . . . Kroon, H. D. (2017). More than 75 percent decline over 27 years in total flying insect biomass in protected areas. Plos One, 12(10). doi:10.1371/journal.pone.0185809

Lister, B. C., & Garcia, A. (2018). Climate-driven declines in arthropod abundance restructure a rainforest food web. Proceedings of the National Academy of Sciences, 115(44). doi:10.1073/pnas.1722477115

Ollerton, J., Winfree, R., & Tarrant, S. (2011). How many flowering plants are pollinated by animals? Oikos, 120(3), 321-326. doi:10.1111/j.1600-0706.2010.18644.x

Bar-On, Y. M., Phillips, R., & Milo, R. (2018). The biomass distribution on Earth. Proceedings of the National Academy of Sciences, 115(25), 6506-6511. doi:10.1073/pnas.1711842115

Komonen, A., Halme, P., & Kotiaho, J. S. (2019). Alarmist by bad design: Strongly popularized unsubstantiated claims undermine credibility of conservation science. Rethinking Ecology, 4, 17-19. doi:10.3897/rethinkingecology.4.34440

Wagner, D. L. (2019). Global insect decline: Comments on Sánchez-Bayo and Wyckhuys (2019). Biological Conservation, 233, 332-333. doi:10.1016/j.biocon.2019.03.005

Cardoso, P., Branco, V. V., Chichorro, F., Fukushima, C. S., & Macías-Hernández, N. (2019). Can we really predict a catastrophic worldwide decline of entomofauna and its drivers? Global Ecology and Conservation, 20. doi:10.1016/j.gecco.2019.e00621

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Banner image caption:Postman butterfly, Heliconius erato or melpomene (blue form). Photo by Rhett Butler/Mongabay.