Classificação da Biblioteca do Congresso dos EUA (LCC)S900-972

1930s(5) activism(8) Africa(12) agriculture(16) American(11) American West(14) animals(20) astrology(7) biography(37) biology(14) birds(9) botany(5) California(9) career(6) chemistry(11) children(8) children's(6) conservation(212) development(10) diary(7) earth(14) ecology(139) economics(11) ecosystems(6) education(9) endangered species(5) environment(203) environmental(29) environmental policy(7) environmental studies(11) environmentalism(68) essay(6) geography(20) geology(16) government(8) Great Depression(16) green(12) history(86) humor(10) Iowa(8) journalism(8) literature(8) management(10) mining(5) Minnesota(5) music(5) National Parks(18) natural resources(31) nature(165) nature writing(11) New Deal(23) New Mexico(6) outdoors(5) photographs(10) photography(10) picture book(5) policy(6) politics(25) pollution(16) queer(6) reference(13) romance(11) science(100) sustainability(17) trans(7) travel(13) trees(9) us(5) usa(25) wilderness(8) wildlife(23)