Spiders eat up to 800 million tons of insects a year

Spiders eat a lot
CC BY 2.0 Thomas Shahan/Flickr

Meanwhile, humans consume a mere 400 million tons in meat and fish.

If you’ve ever fantasized about a world without spiders, you might want to backpedal on that reverie. Because a world without spiders would be a world with A LOT of other creeping crawling things – like 400 and 800 million tons of insects, springtails, and various invertebrates, should other predators not step in to take the spiders' place.

The stunning numbers comes from a study conducted by scientists from the University of Basel in Switzerland and Lund University in Sweden. And while the estimates may be verging on the sensational, they offer fascinating insight into the important role our eight-legged friends play in keeping countless insect pests in check.

The researchers, Martin Nyffeler and Klaus Birkhofer, used data from 65 previous studies. They calculated how many spiders currently reside in seven biomes on the planet. Prepare for another startling number: there are about 25 million metric tons' worth of them. I can’t even conceive of what a single pound of spiders would look like, let alone 25 million metric tons of them.

After extrapolating and calculating and estimating, they came up with the “400 to 800 million tons of prey are being killed by spiders each year” figure.

In comparison:

• Humans together consume an estimated 400 million tons of meat and fish annually.
• Whales feed on 280 to 500 million tons of seafood.
• The world's total seabird population eats an estimated 70 million tons of fish and other seafood.

"These estimates emphasize the important role that spider predation plays in semi-natural and natural habitats, as many economically important pests and disease vectors breed in those forest and grassland biomes," says lead author Nyffeler.

Or to give it another fascinating spin, as the Washington Post points out:

The total biomass of all adult humans on Earth is estimated to be 287 million tons. Even if you tack on another 70 million-ish tons to account for the weight of kids, it's still not equal to the total amount of food eaten by spiders in a given year, exceeding the total weight of humanity. In other words, spiders could eat all of us and still be hungry.

But if you’re now worrying that the world might be inherited by spiders, remember that in turn, they are a source of prey as well. Between 8,000 and 10,000 other predators, parasitoids and parasites feed exclusively on spiders, while spiders at the same time form an important part of the diet of an estimated 3,000 to 5,000 bird species, note the authors.

"We hope that these estimates and their significant magnitude raise public awareness and increase the level of appreciation for the important global role of spiders in terrestrial food webs," adds Nyffeler.

The moral of the story? Love your neighbors and embrace the spiders.

This updated story was originally published on March 15, 2017.

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