In the US, the Sonoran Desert stretches from Arizona to California and further south to Mexico. It's home to some 2,500 different species of plants and animals. But as the population in the nearby city of Phoenix swells beyond four million, the largest desert in North America is feeling the strain. There are fears that urban expansion is putting this fragile ecosystem in danger. But first, after the deadly mudslide in Colombia, we look at the reasons why such devastating natural disasters happen.

And in the US, Fox News advertisers are jumping ship. They are ditching the channel's flagship show "The O'Reilly Factor" amid a slew of sexual harrassment allegations against the host, Bill O'Reilly.