Monty Don presents Shared Planet, the series that looks at the crunch point between human population and the natural world.
In this week's programme the focus is towns and cities, with a report from North America about their largest Swallow, the Purple Martin. Purple Martins are totally dependent on human habitation east of the Rockies for nest sites.
West of the mountain range they largely nest in their ancestral way using abandoned woodpecker cavities.
As we clear land to build the world's towns and cities what is the impact on the natural world and are there ideas to embrace wildlife in built environment planning?
Listen to Shared Planet
You can listen to this episode of Shared Planet on BBC Radio 4 at 11:00am on Tuesday 9 July 2013. More information and a link to listen again can be found on the Radio 4 website.