Count-based PVA allows researchers to assess patterns of population change through time and to evaluate future persistence. We combined state-space models and citizen scientist data to evaluate viability of the western population of monarch butterflies over 36 years. A key feature of our analysis was combining irregular sampling from multiple sites to obtain a single estimate of the total population size using state-space models.
Results/Conclusions
The average population growth rate was negative, u = -0.0762 (λ = 0.927), average population size in the 2000’s was less than 5% of average abundance in the 1980’s, and current quasi-extinction risk is 72% within 20 years. To obtain viable populations, managers could target historic abundance and high enough growth rates to avoid near-term extinction. Improved knowledge about environmental drivers of vital rates is likely necessary to achieve these targets