Christopher Joyce

Scientists who study forests say they've discovered something disturbing about the way prolonged drought affects trees.

It has to do with the way trees drink. They don't do it the way we do — they suck water up from the ground all the way to their leaves, through a bundle of channels in a part of the trunk called the xylem. The bundles are like blood vessels.

When drought dries out the soil, a tree has to suck harder. And that can actually be dangerous, because sucking harder increases the risk of drawing air bubbles into the tree's plumbing.

Second of a two-part series. Read Part 1

California starts the ball rolling Wednesday on a controversial scheme to keep the planet from overheating. Businesses will have to get a permit if they emit greenhouse gases.

Some permits will be auctioned today; the rest are free. The big idea here is the state is putting a ceiling on emissions.

It's a gamble. And for this top-down climate plan to work, it has to usher in a greener, more efficient economy.

California begins a controversial experiment to curb climate change on Wednesday: The state will start rationing the amount of greenhouse gases companies can emit.

It's the most ambitious effort to control climate change in the country. Some say the plan will cost dearly; supporters say it's the route to a cleaner economy.

Here's how the climate deal works. Big companies must limit the greenhouse gases they emit — from smokestacks to tailpipes — and they have to get permits for those emissions. The clock starts Jan. 1.

The fury of the great storm Sandy shocked a lot of people, like John Miksad, vice president of the New York electric utility Consolidated Edison. "We hit 14-foot tides — that was the biggest surprise," he told a press conference this week. "The water just kept rising and rising and rising."

That rising water flooded streets, buildings and parts of the city's underground electricity grid. Hundreds of thousands of New Yorkers lost power. But it might have been worse if the power lines had not been underground.

Some of the weirdest animal behavior is about romance. That's especially true with birds — they croon or dance or display brilliant feathers to seduce the reluctant.

This sort of sexual display apparently has a long pedigree: There's now new evidence that some dinosaurs may have used the same come-on.

The source is a kind of dinosaur that was built like a 400-pound ostrich. It lived about 75 million years ago and is called ornithomimus, meaning "bird mimic."

If you're reading this blog, you're probably into food. Perhaps you're even one of those people whose world revolves around your Viking stove and who believes that cooking defines us as civilized creatures.

Well, on the latter part, you'd be right. At least according to some neuroscientists from Brazil.

Whales are among the great communicators of the animal world. They produce all sorts of sounds: squeaks, whistles and even epic arias worthy of an opera house.

And one whale in particular has apparently done something that's never been documented before: He imitated human speech.

The beluga, or white whale, is smallish as whales go and very cute, if you're into marine mammals. Belugas are called the "canaries of the sea" because they're very vocal.

Few things are as rare as a piece of rock that falls from outer space and crashes onto Earth.

Among the most prized of these meteorites are from Mars. Friday, scientists describe the latest one discovered: It's called Tissint, and this weekend you can buy a piece of it.

The Pacific Island of Guam is experiencing a population explosion — of spiders.

There are more spiders there now than anyone can remember. To get a sense of how weird the situation is, I started out in Maryland. On my front porch, overlooking the Severn River.

At 6:30 in the morning on a cool fall day, I find two spider webs in a matter of five minutes. But if I were on the island of Guam, I might find 70 or 80 spider webs in five minutes.

Anthropologists believe early humans evolved in Africa and then moved out from there in successive waves. However, what drove their migrations has been a matter of conjecture.

One new explanation is climate change.

Anthropologist Anders Erikkson of Cambridge University in England says the first few hardy humans who left Africa might've gone earlier but couldn't. Northeastern Africa — the only route to Asia and beyond — was literally a no man's land.

That fake fruit in the wooden bowls that hotels love to decorate their lobbies with never looks quite right. No, apparently it takes nature to make a fake that looks even better than the real thing.

Last of a five-part series

The droughts that have parched big regions of the country are killing forests.

In the arid Southwest, the body count is especially high. Besides trying to keep wildfires from burning up these desiccated forests, there's not much anyone can do. In fact, scientists are only now figuring out how drought affects trees.

Fourth in a five-part series

Forests in the Southwest have become a fuel stockpile. A century of U.S. Forest Service policy of quashing all fires has allowed forests to become overgrown, and now a warming climate is making the problem worse.

Scientists are trying to defuse these green time bombs. Is it too late?

Third of a five-part series

As the Earth's average temperature creeps upward, climate scientists have predicted record heat waves and droughts. That's what we've seen this summer in the U.S.

The question has become, are we now seeing the real damage climate change can do?