Monarch butterfly populations have declined by over 80% due to habitat loss, pesticides, and climate change, with welfare implications for billions of individual insects.
Monarch welfare sits at the intersection of insect sentience uncertainty and population-scale ecological collapse. If monarchs have even minimal capacity for negative experience — given that they have nervous systems, respond to stimuli, and engage in complex behavior — then the loss of billions of individuals to pesticide exposure, habitat loss, and climate disruption represents a potentially significant welfare concern alongside the conservation crisis. Regardless of sentience questions, the collapse of monarch populations removes a keystone species from North American ecosystems at scale. Planting milkweed and reducing pesticide use are accessible individual contributions.