This beautifully filmed BBC documentary marches through the seasons on Planet Earth. It begins in winter darkness at the North Pole with a mother polar bear coming out of a five-month hibernation with two adorable cubs. A male bear is out looking for food on the ice and having very little luck.

In Africa, elephants and their children are on a long, hard, and dry march through the desert to the Okavango Delta where there is plenty of water. Meanwhile, cranes are flying from Siberia to India and facing turbulent cold air as they head over the Himalayas. Further South, a humpback whale and her calf are making the long journey from tropical to Arctic waters. Along the way these animals must deal with the changes that impact their lives from predators to weather conditions to lack of food. Survival takes patience and courage.

Earth is the first in the DisneyNature lineup of films. Directors Alastair Fothergill and Mark Linfield have made the perfect film accompaniment for Earth Day, a time to celebrate the wonders of the natural world, the diversity of plants and creatures, and the challenge to be better stewards of the earth's treasures. "I cannot but have reverence for all that is called life" said Albert Schweitzer. Watching Earth, we share in this understanding. The filmmakers present the sun and water as precious and the tilt of the Earth as a miracle that makes everything possible. The camera shots draw out our wonder especially during one sequence in a forest where the plants and trees go through the four seasons. There are magical moments which convey the playfulness of animals, such as the mating ritual of a Superb Bird of Paradise performing a dance. Some duck chicks make their first attempt at flight from the nest and land unceremoniously on the ground in a mound of leaves.

Earth is a family film so there are no scenes of graphic violence but be forewarned about the chase sequences involving a cheetah, a group of lions, a band of wolves, and the polar bear as they pursue their prey. The documentary is narrated by James Earl Jones and boasts a top-drawer music score by George Fenton.