Welfare science traditionally focuses on individual animal experience. Scaling welfare assessment to population and species level raises philosophical and methodological questions about aggregating and comparing welfare across individuals.
Scaling welfare from individual to population to species level is not merely a methodological exercise - it shapes what priorities emerge from welfare analysis. If only companion animals and farm animals count, individual interactions with familiar animals drive welfare concern. If wild animals count, the scale of consideration expands to billions of individuals. If invertebrates count, trillions. At each scale, different interventions are prioritised. Welfare science that takes population and species-level analysis seriously produces different conclusions about where welfare investment should be directed than science focused exclusively on familiar individual animals in human care.