Physorg: The balance of biodiversity within North American small-mammal communities is so out of whack from the last episode of global warming about 12,000 years ago that the current climate change could push them past a tipping point, with repercussions up and down the food chain, say Stanford biologists. The evidence lies in fossils spanning the last 20,000 years that the researchers excavated from a cave in Northern California. What they found is that although the small mammals in the area …