Here’s a question: would you rather fight one angry human or 15,000 furious ants? Aggressive naked apes can be a pain, but the smallness of insects is only an upside until they all club together. What if, say, all land insects on Earth were to combine? It’d be a hell of a force to be reckoned with, and one that was explored in a recent study that calculated – for the first time – the combined weight of all land insects and related arthropods on Earth.
The result is pretty intimidating. Apparently, were you to combine the weight of all terrestrial creepy crawlies, you would be faced with a biomass about equal to the weight of all humans and livestock on Earth combined. The researchers' estimates put the total fresh weight of all land insects and arthropods (excluding aquatic/marine species) at around 1 billion metric tonnes. Quite a lump compared to the meatball of human biomass, which is around 400 million tonnes and livestock which is around 600 million tonnes.
Reaching the estimate was a mammoth undertaking. It involved trawling around 500 survey sites for data representing thousands of observations across years of research taken from over 300 locations. Researchers were searching for insights into the biomass of insects beneath the soil, along the forest floor, and scuttling among the leaves of above-ground vegetation.
They were then able to break down the bigger numbers into representative groups. They found that termites were among the biggest contributors to the total mass of all terrestrial insects as a highly successful group of eusocial insects that exist in vast colonies. Termites were responsible for about 40 percent of the biomass in the soil-dwelling group, compared to the 30 percent contributed by ants, springtails, and mites combined.
They estimated that the total biomass of terrestrial arthropods was 300 million metric tonnes at a dry weight, roughly 1 billion metric tonnes at a fresh weight, which is around 150 million metric tonnes of carbon.
The authors explain that the study isn’t without its caveats, including possible under-sampling of certain taxonomic groups and skipping over the natural variability of biomass densities in different biome types. However, it makes for a harrowing first step towards getting a reasonable idea of quite how intimidating an insect army might be in the event of an uprising à la Bug’s Life.
"Arthropods have been described as 'the little things that run the world' because of their central role in multiple ecological processes,” one of the study’s lead authors, Dr Yuval Rosenberg at the Weizmann's Plant and Environmental Sciences Department, said in a statement. “We must take them into account if we're to fully understand humanity's impact on the planet and the possible consequences of climate change.”
"Quantifying arthropod populations establishes a baseline against which we can measure future changes to the arthropod communities and how these changes, in turn, could affect global processes.”
The study was published in Science Advances.