After the Second World War, ecology was reconstructed as a science of complex systems. The ecosystem viewpoint emerged as a central organizing concept and ecologists fashioned a new role for their science in a period dominated by monstrous growth and Cold War concerns. Ecology also became a “subversive” subject as the environmental movement gathered momentum. The immediate postwar decades saw great debate about the relationship between general ecology and human ecology and the relationship between ecology and engineering. Ecologists were challenged to develop close connections to applied science and to pay attention to the needs of society. But how would those needs be determined? How would ecologists communicate their "big ideas" and their value to society? Could ecologists be both servants and critics? The historical debate offers some lessons for contemporary ecology.