The Monarch Conservation Science Partnership is a USGS led group of scientists, managers, and conservation organizations who perform science related to the conservation of monarch butterflies. We come from federal agencies, non profits, and academia and from the three countries where monarchs range (Mexico, Canada, and the United States). To date meetings of the MCSP have been hosted by the USGS John Wesley Powell Center for Analysis and Synthesis in Ft. Collins, CO. PIs include Darius Semmens and Jay Diffendorfer (GECSC) and Wayne Thogmartin (UMESC).
Are we witnessing the end of the migration of monarchs in the eastern U.S.?
What is the issue?
The Eastern, migratory population of monarch butterflies has declined by ~80% over the last decade, despite efforts in Mexico to end illegal logging in the fir forests used by overwintering monarchs. These declines are coincident with the rapid adoption of glyphosate-resistant crops on agricultural lands of the north central U.S.
What are the challenges?
The monarch’s multi-generational migration between overwintering grounds in central Mexico and summer breeding grounds in northern U.S. and southern Canada creates shared management responsibilities across North America.
No national-level monitoring and insufficient basic ecological research (e.g., few habitat-specific estimates of milkweed density) lead to key gaps in our understanding of monarch life history and ecology.
Threats are numerous, including herbicide and pesticide application, loss of natural and conserved areas, and disruption from climate change and consequences of extreme weather, leading to ‘death by a thousand cuts’.
Strategies for mitigating threats are weakly defined.
The Partnership is engaged in considerable research to address information gaps associated with the ecology and conservation of monarch butterflies. Among these efforts include analyses of extinction risk, continental-scale full-annual-cycle demography, threats assessment, overwinter density estimation, milkweed target estimation, and storylines for conservation recovery. Strategies for sampling monarchs and the milkweed that sustains them are being developed. In addition, geospatial tools, both desktop and online, for aiding in conservation planning have been completed.
Quasi-extinction risk and population targets for the Eastern, migratory population of monarch butterflies (Danaus plexippus)
The Eastern, migratory population of monarch butterflies (Danaus plexippus), an iconic North American insect, has declined by ~80% over the last decade. The monarch’s multi-generational migration between overwintering grounds in central Mexico and the summer breeding grounds in the northern U.S. and southern Canada is celebrated in all three countries and creates shared management responsibilities across North America. Here we present a novel Bayesian multivariate auto-regressive state-space model to assess quasi-extinction risk and aid in the establishment of a target population size for monarch conservation planning. We find that, given a range of plausible quasi-extinction thresholds, the population has a substantial probability of quasi-extinction, from 11–57% over 20 years, although uncertainty in these estimates is large. Exceptionally high population stochasticity, declining numbers, and a small current population size act in concert to drive this risk. An approximately 5-fold increase of the monarch population size (relative to the winter of 2014–15) is necessary to halve the current risk of quasi-extinction across all thresholds considered. Conserving the monarch migration thus requires active management to reverse population declines, and the establishment of an ambitious target population size goal to buffer against future environmentally driven variability.
Decline in the eastern migratory monarch butterfly population as surveyed by the World Wildlife Fund-Mexico.
Populations in the high-elevation Oyamel fir forests where eastern monarchs overwinter are indexed by the area over which they occur.
Semmens et al. (2016) provided an adjusted measurement of population size which corrects for observation error.
National Valuation of Monarch Butterflies Indicates an Untapped Potential for Incentive-Based Conservation
The annual migration of monarch butterflies (Danaus plexippus) has high cultural value and recent surveys indicate monarch populations are declining. Protecting migratory species is complex because they cross international borders and depend on multiple regions. Understanding how much, and where, humans place value on migratory species can facilitate market-based conservation approaches. We performed a contingent valuation study of monarchs to understand the potential for such approaches to fund monarch conservation. The survey asked U.S. respondents about the money they would spend, or have spent, growing monarch-friendly plants, and the amount they would donate to monarch conservation organizations. Combining planting payments and donations, the survey indicated U.S. households valued monarchs as a total one-time payment of $4.78–$6.64 billion, levels similar to many endangered vertebrate species. The financial contribution of even a small percentage of households through purchases or donations could generate new funding for monarch conservation through market-based approaches.
A trans-national monarch butterfly population model and implications for regional conservation priorities
The monarch has undergone considerable population declines over the past decade, and the governments of Mexico, Canada, and the United States have agreed to work together to conserve the species. Given limited resources, understanding where to focus conservation action is key for widespread species like monarchs. To support planning for continental-scale monarch habitat restoration, the authors addressed the question of where restoration efforts are likely to have the largest impacts on monarch butterfly population growth rates. They did so by developing a spatially explicit trans-national model of the monarch butterfly's multi-generational life cycle. The authors reported that improving monarch habitat in the north central or southern parts of the monarch range yields a slightly greater increase in the population growth rate than restoration in other regions. However, combining restoration efforts across multiple regions yields population growth rates above replacement with smaller simulated improvements in habitat per region than single-region strategies. These findings suggest that conservation investment in projects across the full monarch range will be more effective than focusing on one or a few regions, and will require international cooperation across many land use categories.