• 11 Natural history
• 10 Animals
• 8 Ecology
• 2 Biotic communities
• 2 Desert ecology
• 2 Forests and forestry
• 2 Habitat (Ecology)
• 2 Marine animals
• 2 Marine ecology
• 1 Caves
• 1 Climatic changes
• 1 Coral reefs and islands
• 1 Deserts
• 1 Forest ecology
• 1 Fresh water
• 1 Grasslands
• 1 Hydrologic cycle
• 1 Jungles
• 1 Mountains
• 1 Ocean
• 1 Plains
• 1 Tropics
• 1 Water

• 12 Discovery Channel (Firm)
• 12 Fothergill, Alastair
• 12 Nihon Hōsō Kyōkai
• 11 BBC Worldwide Americas, Inc.
• 4 Cordey, Huw
• 3 Berlowitz, Vanessa
• 3 Brownlow, Mark
• 3 Linfield, Mark
• 2 Byatt, Andrew
• 2 Keeling, Jonny
• 1 Allen, Penny
• 1 Allen, Penny, Dr
• 1 BBC Worldwide Americas, Inc
• 1 Canadian Broadcasting Corporation
• 1 Warner Home Video (Firm)

• 12 English

• 12 Earth (Planet)
• 1 Cold regions
• 1 Earth
• 1 Eastern Hemisphere
• 1 Everest, Mount (China and Nepal)
• 1 Himalaya Mountains
• 1 Northern Hemisphere
• 1 Polar regions
• 1 Southern Hemisphere
• 1 Tropics
• 1 Western Hemisphere

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