 In the field of ecology he is famous for championing the idea of the trophic cascade, on which he published the provocative “Green World Hypothesis” with colleagues Frederick E. Smith and Lawrence B. Slobodkin.Nelson was also deeply interested in the factors that control human disease and was an adviser to the World Health Organization for many years.Nelson was born on October 16, 1917 in the Cooleemee area of Davie County, North Carolina.