NAT000000 - General
NAT001000 - Animals / General
NAT002000 - Animals / Primates
NAT003000 - Animals / Bears
NAT004000 - Birdwatching Guides
NAT005000 - Animals / Butterflies & Moths
- - -
NAT007000 - Animals / Dinosaurs & Prehistoric Creatures
- - -
NAT009000 - Earthquakes & Volcanoes
NAT010000 - Ecology
NAT011000 - Environmental Conservation & Protection
NAT012000 - Animals / Fish
NAT013000 - Plants / Flowers
NAT014000 - Ecosystems & Habitats / Forests & Rainforests
NAT015000 - Fossils
NAT016000 - Animals / Horses
NAT017000 - Animals / Insects & Spiders
NAT018000 - Ecosystems & Habitats / Lakes, Ponds & Swamps
NAT019000 - Animals / Mammals
NAT020000 - Animals / Marine Life
- - -
NAT022000 - Plants / Mushrooms
NAT023000 - Natural Disasters
NAT024000 - Essays
NAT025000 - Ecosystems & Habitats / Oceans & Seas
NAT026000 - Plants / General
NAT027000 - Reference
NAT028000 - Animals / Reptiles & Amphibians
NAT029000 - Ecosystems & Habitats / Rivers
NAT030000 - Rocks & Minerals
NAT031000 - Seashells
NAT032000 - Seasons
NAT033000 - Sky Observation
NAT034000 - Plants / Trees
- - -
NAT036000 - Weather
NAT037000 - Animals / Wildlife
NAT038000 - Natural Resources
NAT039000 - Animal Rights
- - -
NAT041000 - Ecosystems & Habitats / Mountains
NAT042000 - Animals / Big Cats
NAT043000 - Animals / Birds
NAT044000 - Animals / Wolves
NAT045000 - Ecosystems & Habitats / General
NAT046000 - Endangered Species
NAT047000 - Plants / Aquatic
NAT048000 - Plants / Cacti & Succulents
NAT049000 - Regional

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For subheadings that overlap those in the SCIENCE section, use subjects in this section for works aimed at a lay audience and use subjects in the SCIENCE section for scholarly works and/or works aimed at professionals.