Soil conservation used to be something that only farmers worried about. But Tuesday, April 20 is Dirt Day in Los Angeles and San Francisco -- not to be confused with Earth Day on Thursday. Earth Day encompasses the planet, while "Dirt! The Movie", which airs Tuesday night on Public Broadcasting stations, focuses on the soil beneath our feet. The two cities issued proclamations -- OK, so it's a gimmick -- to focus attention on "safeguarding soil and the billions of organisms it contains," according to Los Angeles filmmakers Gene Rosow and Bill Benenson.

Inspired by William Bryant Logan's book "Dirt, the Ecstatic Skin of the Earth," the film highlights the work of Los Angeles' Andy Lipkis, founder of TreePeople, and other conservation innovators from around the globe. "Why should we care about dirt?" Lipkis asks. "What's the big deal about something we work to keep out of our homes and streets? But Earth's living soil is a huge deal when it comes to sustainability...[and] adaptation to climate change and protection from its effects, in fact, our very lives."

While PBS is showing an hour-long version, a longer version of the film is also available on DVD through the website DirtTheMovie.org, with extensive interviews of Nobel Laureate Wangari Maathai, founder of Kenya's Greenbelt Movement, the mycologist (that's mushroom scientist) Paul Stamens, urban farmers and the women prisoners of New York City's Rikers Island who are finding a new lease on life through gardening. The movie is inspiring community screenings sponsored by garden clubs, environmental groups and citizen activists -- just type in your Zip Code on DirtTheMovie.org.

-- Margot Roosevelt