How can we trust recent claims Earth is on the brink of a sixth mass extinction, when we can’t say with certainty how many species our planet has? Belinda Smith investigates.

A new study rejects the long-held belief that the state of 'walking hibernation' would help polar bears weather climate change.

State of the climate: Broken.

Over many years, glaciers helped form Greenland’s fjords, those narrow and deep inlets in the sea that are often surrounded by steep cliffs and serve as exit routes for the vast ice sheet’s sea-terminating outlet glaciers. And, according to new research, fjords in West Greenland are much deeper...