Trees are vital in the fight against climate change. Why was counting them so controversial?
Sometimes in life the trick is knowing the right question to ask. Scientists had assumed there were billions of trees on earth but then Tom Crowther, an up-and-coming ecologist, wondered if that number was correct. His answer to his own question caused a huge controversy but we may look back on it as a turning point in the climate emergency. Basia Cummings presents this weekâ€™s Tortoise podcast.