Gertrude Duby was a photojournalist and anti-fascist organizer during WWII. In 1940, weary of war, she journeyed to Mexico, where she decided to reinvent herself as a jungle explorer. She bought an old camera and taught herself to use it. Then in 1943, she convinced a government official to let her join an expedition in search of the legendary Lacandon Maya.

The only Maya never conquered by the Spanish, the Lacandon had lived free for centuries deep in the Chiapas jungle. They were rarely photographed and only had sporatic contact with the outside world. Not only did Blom photograph the Lacandon and write a book about her experiences with them.

The systematic deforestation of La Selva Lacandona by loggers, immigrant settlers, and the Mexican government changed the direction of her life yet again. In the 1970s, Blom decided she must speak out, and thus became one of the first environmental activists. She traveled the world, lecturing from first-hand experience about the death of the jungle and showing slide shows of her documentary photographs. In three languages, she wrote hundreds of articles protesting Mexican policies. In 1975 she started El Vivero, a tree nursery that still distributes free trees for reforestation.