The death of the last male northern white rhino in the world raises an interesting question: when does a species pass the point of no return?
Australia was once home to giant fightless birds - much bigger than today's emus and cassawories. But where did they come from, and where did they go?
Large birds once lived across Australia, only to become extinct around the time that giant marsupials and other megafauna died out during the Pleistocene "ice ages".
The "decision science" approach helps avoid unanticipated consequences of programs to bring species such as New Zealand's little bush moa, Waitomo frog, or laughing owl back from extinction.