Gone: Half the Earth's Species

I've known for some time that we are currently amid a mass-extinction period, the 7th in Earth's history, and with each, the planet changes radically. How did I know? I stayed awake in my Geology 101 class, 8 years ago.
This article from Mother Jones reminds us of what scientists have known for decades: Half of Earth's species may be gone by the end of this century (fast for a mass extinction), and it may mean grave consequences for humans, as well.
Thanks to Chuck Mertz for the tip.