In Africa, photographer Nick Brandt assembles an anti-poaching army.

Tom Wylie wants to change the way ocean researchers commute to work

River Rouge, Michigan, is in sniffing distance of a coal-fired power plant, an oil refinery, a sewage-treatment plant, a steel mill, and other industrial polluters.

Mountaintop-removal mines in Appalachia has wiped whole towns from the map.

Sierra traveled to three states to ask people how their lives have been affected by the world's dirtiest energy source--and what they're doing to stop it.

Sierra traveled to three states to ask people how their lives have been affected by the world's dirtiest energy source--and what they're doing to stop it.

The coal-fired Reid Gardner Generating Station dumps its combustion waste into uncovered "ponds" beside the Moapa Band of Paiutes Reservation

Can photos of America's natural wonders inspire a cultural cease-fire?

Why photographer Clark Little risks his neck to share a vision of the natural world that few ever see for themselves