{I have limited time and resources/knowledge to write a full node here, but it is in desperate need of some sort of writeup. So please, help out here.}
(1887 - 1948)
Known for his unusual ability to quantify and communicate scientific concepts to the general public, he holds the title of the father of wildlife ecology. For those who consider themselves environmentalists/conservationists, he is on the list of deities. for some (such as I), he is conservationist Jesus.
Most known for his book, The Sand County Almanac, considered to be the century's, if not eternity's, greatest conservation work. The Almanac and other works/teachings has led to a widespread following and philosophy, based around Leopold's concept of the "Land Ethic." (node that, please)
Another, very notable work is 1933's Game Management. It spawned a new type of science that combined the already established sciences of forestry, agriculture, biology, zoology, ecology, education and communication.