Clashes over an oil pipeline slated to cross historic Native territory in North Dakota continue after more the 140 people were arrested in protests last week. The increasingly high-stakes face-off is one of the biggest actions by Native Americans in years.

For weeks, members of the Standing Rock Sioux have gathered in Cannonball, North Dakota, standing against the Dakota Access pipeline. The government has now halted construction pending reassessment of the project.

Want to visit a place with clean air? Really clean air? Maybe the cleanest of any urban area in the world? We check out a place north of the Arctic Circle that gets an A+ in the newly updated WHO Global Urban Ambient Pollution Database.

Imagine a city where a rush-hour backup might involve just a few cars, and the air is clean because just about everything runs on zero-carbon energy. That's the goal for the Swedish capital, Stockholm.

Hurricane Katrina was bad, but the future could be considerably worse, a new report says. "One of the greatest environmental and economic disasters in the nation's history is rushing toward a catastrophic conclusion, so far unabated and largely unnoticed."

For weeks, members of the Standing Rock Sioux have gathered in Cannonball, North Dakota, standing against the Dakota Access pipeline. The government has now halted construction pending reassessment of the project.

The recent agreement between the US and China to reduce greenhouse emissions made headlines — and rightly so. It was a big step for both nations. But, striking a balance between environmental protection and economic ascendance is much more complicated than that. In China especially, it seems, for every step forward, there are often two steps back. Its actions in Tibet are a prime example, according to a newly-published book.

Florida’s springs are a wonder, bubbling up crystal clear from the state’s limestone aquifer. But persistent drought, agriculture and a growing population are polluting some once pristine springs, turning them green, murky and full of algae.

In Chinese cities like Beijing, a rising awareness about the dangers of air pollution is evident on people's faces. More and more Beijingers are wearing masks to protect themselves from air pollution. But, in order for them to offer any protection at all, they first must be worn correctly.

An underground waste dump on fire is rapidly approaching the site of a landfill with radioactive waste in a small town in Missouri. Environmental activists say the results could be disastrous. Childhood cancers in the area are already on the rise, so why isn't anyone doing anything about it?

The state of Louisiana is disappearing at an incredible rate, and its sinking deltas threaten some of the nation's crucial oil, gas and fisheries industries. But Louisiana has a “Hail Mary” plan to save it. Industry and government have created an unprecedented plan to save and rebuild these wetlands over the next 50 years — and say failure is not an option.

Scientists are establishing a worldwide network of deep-sea listening posts connected to the Internet. It allows researchers -- and the public -- to hear whales, ships, and other underwater sounds. But the US Navy is uneasy.