After three decades of helping save African forests, Mike Fay, a Wildlife Conservation Soci­ety biologist and National Geographic Soci­ety explorer-in-residence, now has redwoods in his blood.

At up to 368 feet (112 meters) and 1,500 years old, redwoods are among the world's tallest and oldest living trees. Researchers are struggling to understand and protect these natural treasures.

Redwood trees, in particular, were valued for their timber — not for their towering beauty or environmental importance. That ...

On day 323 of the transect, in Jedediah Smith Redwoods State Park, I dropped over a log 18 feet in diameter into an abyss of giant botanical pickup sticks, deadfall that had piled up amid the ...