How Global Warming is Changing the Wild Kingdom

The planet is warming, humans are mostly to blame and plants and animals are going to dramatic lengths to cope. That's the consensus of a number of recent studies that used wildlife to gauge the extent of global warming and its effects.

While the topic of climate change is contentious -- including whether the planet is actually heating up -- a growing number of documented shifts in traits and behaviors in the wild kingdom is leading many scientists to conclude the world is changing in unnatural ways.

Among the changes:

• Marmots end their hibernations about three weeks earlier now compared to 30 years ago.
• Polar bears today are thinner and less healthy than those of 20 years ago.
• Many fish species are moving northward in search of cooler waters.
• A fruitfly gene normally associated with hot, dry conditions has spread to populations living in traditionally cooler southern regions.