“A healthy ocean is an ocean with sharks. Take away an apex predator and it’s like removing the lions from the Serengeti. It won’t be long before the gazelle, zebras and wildebeest have multiplied and eaten all the grass. And when the land is laid bare the grazers will starve to death. Predators are crucial for a healthy ecosystem – be it on land or in the water.”

"Conservation" (c. 1938); Published in Round River, Luna B. Leopold (ed.), Oxford University Press, 1966, p. 145-146.
1930s
Context: Conservation is a state of harmony between men and land. … Harmony with land is like harmony with a friend; you cannot cherish his right hand and chop off his left. That is to say, you cannot love game and hate predators; you cannot conserve the waters and waste the ranges; you cannot build the forest and mine the farm. The land is one organism.

Confession of the Lioness: A Novel

"Conservation" (c. 1938); Published in Round River, Luna B. Leopold (ed.), Oxford University Press, 1966, p. 145-146.
1930s

Source: Cold Days

The Tempest, reported in Bartlett's Familiar Quotations, 10th ed. (1919).

From Ferrar, Derek (March 2006). "Papa Mau's Legacy". Ka Wai Ola o OHA. 23 (3):12.

Letter to E.M. Shavrova (September 16, 1891)
Letters

"The Priest of Shiga Temple and His Love" in Death in Midsummer, and Other Stories (1966), p. 59.

Hush Don't Say Anything to God (1999)