From human settlers to alien visitors - when one society meets another, the results can be messy.
The Jamestown settlement may have kicked off the colonization of the New World. But, you'll hear how it also left an indelible mark on its ecosystem and the human landscape. Plus, why the Galapagos Islands haven't been the same since their most celebrated visitor set foot on their rocky shores more than a century ago.
Also: how a spider led the re-population of Krakatau after a devastating volcanic eruption... the "raining" threat of alien microbes... and one man's emergency plan for when Mars attacks.