In the 1800s, 5,000 French farmers working in tiny urban courtyards grew enough food to feed two million Parisians with enough surplus left over to send to London. How did they do it? Why were farmers in the countryside starving, while Parisians could grow an excess of food on small lots in a crowded city? Kate Brown's book Tiny Gardens Everywhere looks at how small gardens often trumped large scale agriculture on farms using nitrogen fertilisers made from fossil fuels, in feeding people, en masse. And with a third of the world's fertilisers held up in the Strait of Hormuz, and global heating accelerating, re-thinking how we grow our food might be just the thing we need right now. 

• Guest: Kate Brown, Distinguished Professor in the History of Science at Massachusetts Institute of Technology and author of Tiny gardens everywhere, a history of urban resilience  - published by Penguin
• Producer: Catherine Zengerer