In 2006, one of the hottest years on record, a "pizzly" was discovered near the top of the world. Half polar bear, half grizzly, this never-before-seen animal might be dismissed as a fluke of nature. Anthony Barnosky instead sees it as a harbinger of things to come.In "Heatstroke, " the renowned paleoecologist shows how global warming is fundamentally changing the natural world and its creatures. While melting ice may have helped produce the pizzly, climate change is more likely to wipe out species than to create them. Plants and animals that have followed the samerhythms for millennia are suddenly being confronted with a world they're unprepared for--and adaptation usually isn't an option.