 Some species of teosinte are critically endangered, and all face a growing threat as agricultural land use expands in Mexico.He campaigned with colleagues at the University of Guadalajara to protect the natural environment of "Zea diploperennis" by creating the 345,000-acre Sierra de Manantlán Biosphere Reserve.He cofounded the Wisconsin chapter of the Nature Conservancy in 1960 and helped establish Hawaii's Natural Areas Law of 1970.