In the 1970s-80s Fowler was Program Director for the National Sharecroppers Fund/Rural Advancement Fund. Following this, he served as Professor and Director of Research in the Department for International Environment & Development Studies at the Norwegian University of Life Sciences in Ås, Norway. He also led the International Conference and Programme on Plant Genetic Resources at the Food and Agriculture Organization of the United Nations (UN) in the 1990s. There, he produced the UN's first global assessment of the state of the world's crop diversity and was the chief author of the Food and Agriculture Organization's Global Plan of Action for Plant Genetic Resources. He subsequently supervised the negotiations that led to its adoption by 150 countries in 1996.