Elizabeth Shogren

At about 300 colleges across the country, young activists worried about climate change are borrowing a strategy that students successfully used in decades past. In the 1980s, students enraged about South Africa's racist Apartheid regime got their schools to drop stocks in companies that did business with that government. In the 1990s, students pressured their schools to divest Big Tobacco.

This time, the student activists are targeting a mainstay of the economy: large oil and coal companies.

A gluttonous predator is power-eating its way through reefs from New York to Venezuela. It's the lionfish.

And although researchers are coming up with new ways to protect some reefs from the flamboyant maroon-striped fish, they have no hope of stopping its unparalleled invasion.

Lad Akins has scuba dived in the vibrant reefs of the Bahamas for many years. But when he returned a couple years ago, he saw almost no fish smaller than his hand.

Amber Bartlett was waiting last Friday for her kids to come home from school. One of them called from the entrance to the upscale subdivision near Little Rock, Ark., to tell her the community was being evacuated because of an oil spill. Bartlett was amazed by what she saw out her front door.

"I mean, just rolling oil. I mean, it was like a river," she says. "It had little waves in it."

Environmentalists have a hope.

If they can block the Keystone XL pipeline, they can keep Canada from developing more of its dirty tar sands oil. It takes a lot of energy to get it out of the ground and turn it into gasoline, so it has a bigger greenhouse gas footprint than conventional oil.

Tens of thousands of protesters turned out on the National Mall Sunday to encourage President Obama to make good on his commitment to act on climate change.

In his Inaugural address from outside the U.S. Capitol, the president said: "We will respond to the threat of climate change knowing that the failure to do so would betray our children and future generations."

Just a few weeks later, next to the Washington Monument, Paul Birkeland was one of a couple dozen people holding a long white tube above their heads.

President Obama pulled out a surprise in his inaugural address on Monday. After barely mentioning climate change in his campaign, he put it on his short list of priorities for his second term.

"We will respond to the threat of climate change, knowing that the failure to do so would betray our children and future generations," he said. Today the White House had scant detail on what the president plans to do.

Modern scientists trying to understand climate change are engaged in an unlikely collaboration — with two beloved but long-dead nature writers: Henry David Thoreau and Aldo Leopold.

The authors of Walden and A Sand County Almanac and last spring's bizarrely warm weather have helped today's scientists understand that the first flowers of spring can continue to bloom earlier, as temperatures rise to unprecedented levels.

Just a few years ago, Georgia Power generated nearly three-fourths of its electricity with coal. Last year, for the first time, natural gas edged out coal, and just this week the company announced plans to close 10 coal-fired power generators within the next few years.

"We do recognize this is a historic event for our company. We've never announced this many closings at one time," says Mark Williams, a company spokesperson.

Canadian researchers have used the mud at the bottom of lakes like a time machine to show that tar sands oil production in Alberta, Canada, is polluting remote regional lakes as far as 50 miles from the operations.

An increasingly large share of U.S. oil comes from Canada's tar sands. There are environmental consequences of this development, but until recently, Canadian regional and federal governments left it to the industry to monitor these effects.

An east Texas landowner was so determined to block the Keystone XL pipeline from coming through his forest that he took to his trees and built an elaborate network of treehouses eight stories above the ground.

"It popped into my head a long time ago, actually," says 45-year-old David Daniel. "If I had to climb my butt on top of a tree and sit there, I would. It started with that."

It turned out to be Daniel's last stand in a long battle against the Keystone XL, a pipeline project that would bring oil from Canada all the way to refineries in the Texas Gulf Coast.

The air reeks so strongly of rotten eggs that tribal leader Wes Martel hesitates to get out of the car at an oil field on the Wind River Reservation in Wyoming. He already has a headache from the fumes he smelled at another oil field.

Sandy hit the East Coast on Monday and knocked out power for millions of people. Utility companies face major challenges to get power back online after the massive storm.

In previous elections, candidates from both parties have campaigned on pledges to be environmental presidents. This time, neither candidate is talking much about cleaning up the air or protecting scenic lands.

Instead, the debate has focused on whether and how much environmental regulations hurt businesses, especially the energy industry.

Mostly it's been GOP candidate Mitt Romney criticizing President Obama for what he sees as overzealous environmental regulations that strangle the economic recovery.

Environmental Rules

President Obama named a new national monument on Friday: Chimney Rock in southwestern Colorado. With two sandstone spires soaring from a mesa, not only is Chimney Rock a spectacular place; it also provides a fascinating glimpse into the ancient people who lived in that region more than 1,000 years ago.

Reducing greenhouse gases and saving the polar bears tend to dominate discussions on climate change. But to the booming world population, one climate change issue may be even more pressing – hunger.

A new report by a leading international relief agency warns that climate change will increase the risk of large spikes in global food prices in the future, and lead to more hungry people in the world. That's because extreme weather like droughts, floods and heat waves are predicted to become much more frequent as the planet heats up.