In the course of thirty-five years of research on complexity David Green has investigated problems as diverse as forest ecology, proteins, and social networks. He proved the universality of networks in complex systems and is author of 9 books and over 160 research articles on complexity theory, evolutionary computing, and multi-agent systems. An early pioneer of the World Wide Web as a distributed information resource, he also played a leading role in national and international efforts to create a coordinated web of information sources about the world's biodiversity and environments.