Monty Don presents Shared Planet, the series that looks at the crunch point between human population and the natural world.
In this programme Howard Stableford reports from Connecticut on the complex decline of the once very ubiquitous Chimney Swift, a story Monty Don believes is the paradigm for the series.
The wider issues of human population and nature are exploreed in the studio with Lord May, past president of The Royal Society and from Vienna, Professor Wolfgang Lutz, a specialist in human population dynamics.
Listen to Shared Planet
You can listen to this episode of Shared Planet on BBC Radio 4 at 11:00am on Tuesday 11 June 2013. More information and a link to listen again can be found on the Radio 4 website.