Monarch butterfly overwintering colonies in Mexico and California face threats from habitat degradation, climate change, and logging that affect the welfare of billions of individuals.
Overwintering monarchs face welfare threats primarily from habitat degradation that reduces the thermal buffering provided by dense forest canopy. Monarchs without adequate canopy protection are exposed to freeze events that kill large numbers of individuals. At the individual butterfly level, the capacity for suffering is uncertain due to their simple nervous systems, but massive mortality events cause the loss of billions of potential experiences. From an ecological welfare perspective, overwintering site degradation threatens the entire eastern monarch population's viability, with cascading consequences for the many other species that interact with monarch populations. Protecting overwintering habitat through community-based conservation, sustainable forestry alternatives, and international agreements represents the most important single conservation action for monarch welfare.