How Many Spiders Are There on the Planet?
WouterA recent study estimates there are quadrillions of spiders on the planet. These eight-legged carnivores eat 400 million to 800 million tons of prey per year. This means that they could eat the entire human population in less than a year.
The study was conducted by a team of researchers at the Brandenburg University of Technology in Cottbus-Senftenberg, Germany. They gathered data from published studies on spider biomass in different environments. They used two simple models to estimate the amount of food the spiders needed to survive.
They found that the average amount of spiders that lived on a square meter of land was 131. That is a staggering number. They were able to extrapolate this figure from field observations to calculate the number of tons of spiders in the world.
As far as diet, most spiders eat insects. Interestingly, some species are herbivorous. They may eat the bodies of their prey or discard the wings.
The researchers estimated the total weight of spiders on the planet to be around 25 million metric tons. They also estimated the amount of insect and other invertebrate prey that the spiders eat each year. The estimated annual prey kill is similar to the amount eaten by all whale species.
The authors concluded that the annual global prey kill is a strong indicator that spiders exert substantial predation pressure on the insect populations. This suggests that spiders play a key role in controlling insect pests.
