Joel Sartore's most memorable eye to eye grizzly bear experience was when he was charged by a mama bear protecting her cubs near Brooks Falls, Alaska.

They say not to run if a grizzly charges you. Joel didn't. His feet were frozen to the ground. When the mama ambled off to collect her cubs a mere ten seconds later, Joel sat where he had stood.

He wondered if he'd survive this assignment - photographing grizzly bears for the "National Geographic Magazine".

Well, he did, and his knowledge of bears and his incredible photographic collection of them grew, both to be featured in "Face to Face with Grizzlies".

He contrasts the ancient range of grizzlies when they used to roam down as far as Mexico with their current status, mostly in Yellowstone and Glacier National Parks.

He looks at the future of grizzly bears - and how much that future depends on people.