大象传媒

Around the One Planet office we often set ourselves pub quiz style questions - to keep us awake whilst editing parts of the show very late at night. "What is the perfect size of a city?" Mike asked last week. And it turns out there's all kinds of economic papers written trying to answer that very question. So in this week's show we went in search of the answer ourselves, and with the population of the world's cities expected to grow by over three billion between now and 2050, we're pretty sure others will be interested too.

Mike goes to Nottingham to hang out with Professor Tim Heath, an urban planning expert from the local university. And we hear from people living in three very different cities - Edmonton in Canada (population 1million), Ghana's capital Accra (population 3million), and Sao Paulo in Brazil (population 12million) - who share thoughts on what would make their hometown a better place. In the case of Sao Paulo it's the transport that appears the main problem as our reporter finds out on a long bus journey through the city.

Also in the show, we sit down and chat with Baaba Maal - African music legend, and a man keen to talk about climate change. Throw in some environmental psychology, and news of a the Gorilla King, and the programme's as busy as ever. Tune in or download, have a listen and let us know what you think. You know the email address by now, oneplanet@bbc.com, or remember you can always join the conversation on our Facebook page, the link is below.