Letter: To Yoda's law listen very carefully for biodiversity

From Bruce Denness, Whitwell, Isle of Wight, UK

Sarab Sethi and his team have developed a device that cheaply gauges rainforest biodiversity by interpreting the collective sound of different animals (6 October, p 10). I predict the results will reflect “Yoda's law“.

This arose from efforts to maximise crops and is also called the “-3/2 distribution law”: if you chart the mean weight of plants against their number per unit area on a double-logarithmic plot, you get a straight line with a downward slope of –3/2. This quantifies the observation that the more plants are crowded, the smaller each is liable to be.

The finding was later extended to the distribution densities of animals and birds – and described as a law in search of a theory (16 June 1983, p 765). It should help in defining the area required to protect species. For instance, predatory birds require more territory than predatory mammals, followed by herbivorous birds, primates and herbivorous mammals.