Arachnophobia is a common and powerful fear. Spiders sit high in the pantheon of species that have an outsized terror-to-danger ratio. But, unsettling though they may be, the eight legged to excel at keeping six-limbed pests in check. They prey upon insects in vast quantities, while, for the most part, leaving people alone.
In research published this week in the Science of Nature, Matryn Nuffeler of the Unversity of Basel, in Switzerland, and Kalaus Birkhofer of Lund University in Sweden, attempt to put some numbers on spider’s dining habits. Starting with available data on the mass of spiders found per square metre in Earth’s main habitat types – forests, grasslands, field or crops and so on – they calculated the amount of prey required in each habitat to support the weight of spiders there, based on spider’s known food requirements per unit of body weight. That done, they extrapolated their habitat-based studies to the whole planet….
Their conclusion was that there are 25m tonnes of spiders around the world and that collectively…they… consumer between 400m and 800m tonnes of animal prey per year. This puts spiders in the same predatory league as humans as a species.
The entire article can be found on page 82 of the 18 March edition of The Economist magazine