In Episode 3 we welcome our first guests on the podcast from the natural sciences – Professor Phil Haygarth, Professor Paul Withers, Dr Kirsty Forber and Dr Shane Rothwell – to discuss the key challenge for our food system of phosphorus. Phosphorus is an essential building block of life, and so an essential nutrient in our food and agriculture. In the last 80 years or so, massive growth of mineral phosphorus in farming has been key to the boom in food production. But too much phosphorus flowing through the rural and natural environment also has profoundly negative environmental impacts, not least for water, on which human and non-human life also utterly depends. And the leaching of phosphorus into rivers, lakes and increasingly oceans sets up a one-way pipeline that is fast depleting this essential but finite resource. With this fantastic panel, we discuss these serious challenges, what is, is not and could be done about them, and all the challenges to the very institutions of contemporary science this brings to light.