On Sunday 14th May, Ryosuke Iritani gave a scientific outreach talk at Mathcafe. He focused on spatial biodiversity as a chief topic and how to use mathematics to estimate, and make inferences for, the biodiversity. He explained the measurement of biodiversity from the axiomatic viewpoint, that is, he explained what properties should be satisfied by the quantity that is supposed to measure biodiversity. He then moved on to explaining an application of generating functions to biodiversity measures. He finished his talk by saying that mathematics is not only useful to science but also a life-time fun hobby.