Most of us think we've been around the block a few times and know something about the natural world we live in. Whether from our education, from visiting zoos and natural history museums or from watching Animal Planet or the Discovery Channel, we feel we have a decent understanding of the animal species that share the world with us human beings.

It's been one of the great accomplishments of David Attenborough, the celebrated British broadcaster, 1) to show us that we really didn't know as much about the natural world as we thought we did, 2) to take us on televised journeys that vastly increased our knowledge, and 3) to do it all with enthusiasm, charm and intelligence that aren't the slightest bit snooty.

Attenborough, 81, the younger brother of actor-director Richard Attenborough, has worked for the BBC since 1952. He began making documentaries about natural history in the early 1970s and came to international attention in 1979 for his 13-part BBC series "Life on Earth," which was watched by an estimated 500 million people worldwide.

Attenborough's most widely seen documentary series of recent years are packaged in "The BBC Natural History Collection Featuring Planet Earth," a new 17-disc DVD boxed set released by BBC Video in anticipation of Earth Day on Tuesday.

The set includes:

"Planet Earth: The Complete Series" (2006, five discs): Narrated and co-written by Attenborough, this 11-part series, winner of four Emmy Awards, including outstanding nonfiction series, is an extraordinary achievement. Filmed in highdefinition over five years in 62 countries on every continent, "Planet Earth" presents one mind-boggling image after another — from aerial views of African wild dogs working together on a hunt to the ever-changing blue bird of paradise from Papua New Guinea and the stunning snow leopard of northern Asia.

Bonus features include short behind-the-scenes documentaries about how each episode was made, plus a three-part documentary, "Planet Earth — The Future," that explores the issues of endangered species and environmentalism.

When "Planet Earth" aired in the United States for the first time, Attenborough's narration was replaced by Sigourney Weaver's. But this DVD version restores Attenborough's original narration.

"The Blue Planet: Seas of Life" (2001, five discs): Also written and narrated by Attenborough, this pathbreaking documentary series reminds us that 70 percent of planet Earth is covered by water, with the Pacific Ocean taking up half of the planet. In eight episodes, marine life ranging from the largest animal on the planet, the blue whale ("far bigger than even the biggest dinosaur"), to infinitesimal species, from frozen seas to coral reefs, is shown in its watery habitats.

A bonus disc presents four additional programs, including ones about creatures living at the bottom of the Amazon River and sharks dwelling in underwater volcanoes, plus behind-the-scenes footage, interviews with series producer Alastair Fother-gill, cameraman Doug Allen and researcher Penny Allen, and more.

"The Life of Mammals" (2002, four discs): This worldwide exploration of mammal life is also written and narrated by Attenborough, who appears as the onscreen host in many different habitats, unlike "Planet Earth" and "The Blue Planet," where he is off-camera. The series is divided into chapters on "Insect Hunters," "Plant Predators," "Chisellers," "Meat Eaters" (looking at "the two great tribes of carnivores — the cats and the dogs"), "Opportunists," "Return to Water," "Life in Trees" and "Social Climbers," as well as a general survey of mammal diversity and a report on human mammals. Bonus features include behind-the-scenes looks at the making of the series.

"The Life of Birds" (1998, three discs): Attenborough writes, narrates and hosts this series, whose photographers went to 42 countries to photograph 300 different species. It explores the history of birds, going back to the days of flying reptiles, looks at how birds fly, the role of feathers, the "demands of the egg," the task of fishing, meat-eating and searching for insects, and much more. The 10-episode series does not include any bonus features.

One caveat: Although each of these series offers many educational lessons, they are not for young children. While Attenborough and his crew don't dwell on violence and gore, they don't soften the reality of predatory killing. "Planet Earth," for example, has a rough scene in which a large pride of lions set upon an elephant, while "The Blue Planet" includes a scene in which a group of killer whales attacks a gray whale calf, its outnumbered mother unable to protect it.

Not enough nature for you? BBC Video also is releasing this week "David Attenborough: Wildlife Specials", a two-disc collection from the mid-1990s featuring documentaries on polar bears, crocodiles, leopards, eagles, humpback whales and wolves.