“There is time not only to see who has done what, but to speculate why.”
Aldo Leopold book A Sand County Almanac
“January: January Thaw”, p. 4.
A Sand County Almanac, 1949, "January Thaw", "February: Good Oak" & "March: The Geese Return"
Aldo Leopold was an American author, philosopher, scientist, ecologist, forester, conservationist, and environmentalist. He was a professor at the University of Wisconsin and is best known for his book A Sand County Almanac , which has sold more than two million copies.
Leopold was influential in the development of modern environmental ethics and in the movement for wilderness conservation. His ethics of nature and wildlife preservation had a profound impact on the environmental movement, with his ecocentric or holistic ethics regarding land. He emphasized biodiversity and ecology and was a founder of the science of wildlife management.
Wikipedia

“There is time not only to see who has done what, but to speculate why.”
Aldo Leopold book A Sand County Almanac
“January: January Thaw”, p. 4.
A Sand County Almanac, 1949, "January Thaw", "February: Good Oak" & "March: The Geese Return"
“In our attempt to make conservation easy, we have made it trivial.”
Aldo Leopold book A Sand County Almanac
Source: A Sand County Almanac, 1949, "The Land Ethic", p. 210.
"Wilderness as a Form of Land Use" [1925]; Published in The River of the Mother of God and Other Essays by Aldo Leopold, Susan L. Flader and J. Baird Callicott (eds.) 1991, p. 137-138.
1920s
"The Farmer as a Conservationist" [1939]; Published in The River of the Mother of God and Other Essays by Aldo Leopold, Susan L. Flader and J. Baird Callicott (eds.) 1991, p. 259.
1930s
Aldo Leopold book A Sand County Almanac
“Wisconsin: The Sand Counties”, p. 102.
A Sand County Almanac, 1949, "Wisconsin: Marshland Elegy," "Wisconsin: The Sand Counties" "Wisconsin: On a Monument to the Pigeon," and "Wisconsin: Flambeau"
Aldo Leopold book A Sand County Almanac
“November: A Mighty Fortress”, p. 77.
A Sand County Almanac, 1949, "November: Axe-in-Hand," "November: A Mighty Fortress," and "December: Pines above the Snow"
Aldo Leopold book A Sand County Almanac
Source: A Sand County Almanac, 1949, "Wilderness", p. 199.
Aldo Leopold book A Sand County Almanac
Source: A Sand County Almanac, 1949, "The Land Ethic", p. 205.
Aldo Leopold book A Sand County Almanac
“April: Come High Water”, p. 25.
A Sand County Almanac, 1949, "April: Come High Water," "April: Draba," "April: Bur Oak," & "April:Sky Dance"
Aldo Leopold book A Sand County Almanac
Source: A Sand County Almanac, 1949, "Conservation Esthetic", p. 174.
“Do we realize that industry, which has been our good servant, might make a poor master?”
"A Plea for Wilderness Hunting Grounds" [1925]; Published in Aldo Leopold's Southwest, David E. Brown and Neil B. Carmony (eds.) 1990 , p. 160.
1920s
Aldo Leopold book A Sand County Almanac
“Wisconsin: Marshland Elegy”, p. 96.
A Sand County Almanac, 1949, "Wisconsin: Marshland Elegy," "Wisconsin: The Sand Counties" "Wisconsin: On a Monument to the Pigeon," and "Wisconsin: Flambeau"
Aldo Leopold book A Sand County Almanac
“April: Bur Oak”, p. 30.
A Sand County Almanac, 1949, "April: Come High Water," "April: Draba," "April: Bur Oak," & "April:Sky Dance"
Aldo Leopold book A Sand County Almanac
Source: A Sand County Almanac, 1949, "The Land Ethic", p. 209.
Aldo Leopold book A Sand County Almanac
Source: A Sand County Almanac, 1949, "Conservation Esthetic", p. 176-177.
Aldo Leopold book A Sand County Almanac
“May: Back from the Argentine”, p. 35.
A Sand County Almanac, 1949, "May: Back from the Argentine," "June: The Alder Fork," "July: Great Possessions," and "July: Prairie Birthday"
“Relegating grizzlies to Alaska is about like relegating happiness heaven; one may never get there.”
Aldo Leopold book A Sand County Almanac
Source: A Sand County Almanac, 1949, "Wilderness", p. 199.
Aldo Leopold book A Sand County Almanac
Source: A Sand County Almanac, 1949, "The Land Ethic", p. 224-225.
Aldo Leopold book A Sand County Almanac
Source: A Sand County Almanac, 1949, "The Land Ethic", p. 203-204.
Aldo Leopold book A Sand County Almanac
“November: Axe-in-Hand”, p. 68.
A Sand County Almanac, 1949, "November: Axe-in-Hand," "November: A Mighty Fortress," and "December: Pines above the Snow"
Aldo Leopold book A Sand County Almanac
Source: A Sand County Almanac, 1949, Foreword, p. viii.