As the number of humans on Earth has nearly doubled over the past four decades, the number of bugs, slugs, worms and crustaceans has declined by 45 per cent, say researchers.
Meanwhile, the larger loss of wildlife big and small across the planet may be a key driver of growing violence and unrest, said another study in the journal Science as part of a special series on disappearing animals.
Invertebrates are important to the Earth because they pollinate crops, control pests, filter water and add nutrients to the soil.
The decline of invertebrates is similar to that of land-based vertebrates, according to an analysis of scientific literature by an international team including Ben Collen of University College London.
Among animals with backbones that live on land, 322 species have disappeared in the past five centuries, and the remaining species show about a 25 per cent decline in abundance.
"We were shocked to find similar losses in invertebrates as with larger animals, as we previously thought invertebrates to be more resilient," says Collen.