" Within the ESA, a frustrated Shelford started the Ecologists’ Union when his Committee on Preservation of Natural Conditions ceased to function due to the political infighting over the ESA stance on conservation.
Sociolog Lewis Mumford je bil tisti, ki jeponesel ideje Georgea Perkinsa Marsha do modernega zanimanja leta 1955 na konferenci, "Man´sRole in Changing the Face of the Earth.