Academia and government often ignore or deny the impact of population growth on the environment. However, key scientific institutions and reports confirm that population growth is a major driver of climate disruption and other environmental crises. We review the environmental science of population growth. Issues that block dialogue are discussed, such as growthism, anthropocentrism, denial, religious and cultural taboos, fear of being called a racist, the issue of rights claims, seeking political power through numbers, the framing of social justice issues, and sophistical claims regarding ‘racism’. We examine examples of denial about population in academia and government. We explore ways forward to gain dialogue, and we also consider success stories. We conclude that population growth, like overconsumption, must be foregrounded to create ecologocally sustainable economies and a sustainable future.