Environment

Running underneath the rolling hills of Tennessee lies a still-mysterious and remote network of caverns. Many of those caves shelter fragile ecosystems, and biologist Jerry Lewis is helping to discover and protect some of those ecosystems from man's destruction.

Running underneath the rolling hills of Tennessee lies a still-mysterious and remote network of caverns. Many of those caves shelter fragile ecosystems, and biologist Jerry Lewis is helping to discover and protect some of those ecosystems from man's destruction.

Mingma Norbu Sherpa was one of 24 conservationists killed in Nepal this week in a recent helicopter crash near Kathmandu. A child of the Himalayas, Sherpa, 50, was an official with the World Wildlife Fund who helped change conservation practices around the world.

Mingma Norbu Sherpa was one of 24 conservationists killed in Nepal this week in a recent helicopter crash near Kathmandu. A child of the Himalayas, Sherpa, 50, was an official with the World Wildlife Fund who helped change conservation practices around the world.

Conservationist Bruce Beehler is pushing through a wild and previously unexplored jungle in search of a mysterious and poisonous bird native to Papua New Guinea, the pitohui. His only lead and guide is a local shaman, who uses poison from the bird in his rituals.

Conservationist Bruce Beehler is pushing through a wild and previously unexplored jungle in search of a mysterious and poisonous bird native to Papua New Guinea, the pitohui. His only lead and guide is a local shaman, who uses poison from the bird in his rituals.

National Geographic Society Explorer-in-Residence Fay has uncovered a staggering loss: During a survey of Chad -- a country of vast spaces at the heart of Africa -- he stumbled on at least 100 dead elephants near an elephant preserve, killed for their ivory tusks.

National Geographic Society Explorer-in-Residence Fay has uncovered a staggering loss: During a survey of Chad -- a country of vast spaces at the heart of Africa -- he stumbled on at least 100 dead elephants near an elephant preserve, killed for their ivory tusks.

The Leuser Ecosystem, one of the world's richest yet least-known forest systems, is increasingly threatened by logging and encroachment by a burgeoning population. We fly into the heart of the forest to profile the conservationists trying to keep it pristine for future generations.

The Leuser Ecosystem, one of the world's richest yet least-known forest systems, is increasingly threatened by logging and encroachment by a burgeoning population. We fly into the heart of the forest to profile the conservationists trying to keep it pristine for future generations.