Editor's Note: We're following the climate summit in Copenhagen but we're not taking sides – we're reporting the facts. As part of our Planet in Peril report, Anderson traveled to the rainforest to examine the impact of logging, agribusiness and construction on the world's largest rainforest. Don't miss more of his Planet in Peril reporting on Sunday at 8 p.m. and 11 p.m. ET.

Anderson Cooper | BIO
AC360° Anchor

The Amazon rainforest is the largest in the world and covers nearly 70 percent of Brazil. The rainforest produces about 20 percent of the Earth's oxygen and plays a big role in controlling the climate of the entire planet. The Amazon also is home to more species of plants and animals than any other ecosystem on Earth, 30 percent of the world's total.

About one-fifth of the Amazon has disappeared in the past three decades. The causes are many: Logging, both legal and illegal; construction of homes and roads; and agri-business clearing land to plant crops or graze cattle.

The Brazilian government says the situation is getting better and that federal police are cracking down on illegal logging, in particular. But critics say there aren't enough agents on the ground and that more land needs to be put under federal protection.

Sanjay Gupta | BIO
AC360° Contributor

Lake Chad once was the sixth-largest lake in the world, but in 45 years it has shrunk to half the size of Rhode Island – only 10 percent of its earlier size.

The shallow body of water borders four countries: Cameroon, Chad, Niger and Nigeria – and provides water to 20 million people.

In Nigeria, the shrinking lake has a huge effect on human health – farmers find it more difficult to siphon water into irrigation and they have a harder time growing food, which means people become more vulnerable to diseases like malaria and yellow fever.

Scientists say water diversion (irrigation and new dams on nearby rivers) and drought are equally to blame for the shrinking lake levels.

Keep Reading...

Evidence of deforestation near the Congo Arriba river in Panama's Darien Province, April 2008.

David Ariosto
CNN

Hunched over a campfire in eastern Panama, Embera tribesman Raul Mezua chanted a song his grandfather taught him when he was a boy.

The words are memorized, passed down from an aging generation to a new group of tribal youths.

"The song means a lot to me," Mezua told CNN, the fire's dying embers splashing a red glow across his face. "But I don't know what it means."

It's not just the song but their language and culture that Mezua and his tribe fear losing as deforestation from logging and cattle ranching threatens the rainforest that is part of their identity.

But recent trends could usher in a welcome reversal for Mezua and his tribe. Rural workers are migrating toward cities in search of jobs, and forests are re-emerging where now abandoned farms and cattle ranches once flourished, according to a 2009 report from the U.N. Food and Agriculture Organization.

Keep Reading...

Anderson Cooper | BIO
AC360° Anchor

Editor's Note: Authorities have uncovered an underground tunnel between Tijuana, Mexico and San Diego, California. Anderson will be live from this new tunnel tonight at 10 p.m. ET.

Anderson Cooper | BIO
AC360° Anchor

Heading to San Diego, where once again an enormous tunnel has been discovered. It was being built to smuggle people and/or drugs from Tijuana into the US.

The level of sophistication of these tunnels is extraordinary. In addition to lighting, electrical, and ventilation systems, this new one even has an elevator on the Tijuana side. It was still being built when it was discovered, and authorities arrested more than a dozen men inside.

A few years ago we got an exclusive look at another tunnel U.S. authorities had just discovered that opened up into a warehouse on the U.S. side. It wasn't clear how long that one had been in operation. Watch our report from 2006 here.

Tonight we'll take you deep underground inside the new tunnel, and we'll update you on the war Mexico is fighting against drug traffickers - a war that has claimed more than 7,000 lives this year alone.

Dr. Sanjay Gupta | BIO
AC360° Contributor
CNN Chief Medical Correspondent

Located in the South Pacific, the Carteret Islands are fighting a losing battle against the ocean. It's estimated the six islands will disappear into the water by 2015. Papua New Guinea plans to relocate the Carteret's 2,000 residents.

But a debate centers on what is causing these islands to disappear: Is global warming to blame, or are the islands sinking into the sea, or have the residents permanently damaged the reefs that help to protect the islands from the ocean?

Program Note: Tune in tonight for Gary Tuchman's full report on James Arthur Ray's self-help program. AC360° at 10 p.m. ET.