Nancy Unger is professor of history at Santa Clara University and the author of "Beyond Nature's Housekeepers: American Women in Environmental History."

(CNN) -- Earth Day is the time of year to hear the usual polarized debates between liberals who lament humanity's reckless use of natural resources and conservatives who deny any human role in climate change and echo Sarah Palin's call for industry to "drill, baby, drill."

This division is familiar, but it hasn't always been this way. After all, it was President Nixon who established the Environmental Protection Agency and signed the Clean Air Act. Long before that, social conservatives were in the vanguard of environmental activism in the United States, in part because of their traditional views about women.

Lydia Adams-Williams, conservationist and writer, summed up a widely held belief when she proclaimed in 1908, "Man has been too busy building railroads, constructing ships, engineering great projects and exploiting vast commercial enterprises to take the time necessary to consider the problems which concern the welfare of the home and the future." It fell to women, she declared, "to educate public sentiment to save from rapacious waste and complete exhaustion the resources upon which depend the welfare of the home, the children, and the children's children."...