Salmon in Alaska's Bristol Bay are heading to the ocean a whole year earlier than they used to because of climate change and other fish.

Just one in three of the world's longest rivers is still free-flowing, new research shows.

"Most rivers are eroding at about a tenth of a millimeter per year. This is about 100 times that amount."

Hundreds of dams proposed to control flooding of the Mekong River basin would threaten food security and the envirnoment, researchers warn.