Bird and bat droppings might not sound precious, but guano was once so prized it shaped agriculture, trade and even warfare. Professor Adam Rutherford and Jessica Fostekew explore the surprising story of this pongy but remarkable substance, joined by ecologist Kate Jones, ornithologist Tim Birkhead and comedian Zoe Lyons.
From vast seabird colonies off the coast of Peru to bat-filled caves in the tropics, they discover how guano became one of humanity's most valuable natural resources, powering farming booms, helping to drive the production of gunpowder and sustaining entire ecosystems. Along the way they uncover why seagulls may be as dastardly as they seem with their targeted 'drops', what scientists can learn from ancient 'poo cores' and whether it's weird to have never spotted a bat. Most importantly, they discover why nature's least glamorous resource may be one of its most important.
Producer: Mel Brown A BBC Studios Production