Our parent organization, the North American Butterfly Association (NABA), recently contributed to research and a white paper related to monarch population numbers. See the full report in the PDF, here, and read more below. 

Monarchs are the iconic American butterfly species. Concern for the survival of this species, amidst reports of declining numbers, shrinking habitat, environmental toxins and climate change, have spurred public interest in conservation efforts to assist monarchs in their plight. For this we are grateful. 

Of the 456 butterfly species tracked by NABA, there are 320 species with trends less positive that monarch butterflies. These findings are consistent with other recent analyses of large-scale insect data, documenting species decline. While we hope individuals, communities and organizations will continue to invest in monarch research, public education and habitat restoration, we encourage everyone to engage with us, their local, native plant society, or nearest NABA Chapter, to plant native for all butterfly species, which depend upon native host plants for reproduction and resilience. 

PAPER ABSTRACT: Many insects are in clear decline, with monarch butterflies (Danaus plexippus) drawing particular attention as a flagship species. It is well documented that, among migratory populations, numbers of overwintering monarchs have been falling across several decades, but trends among breeding monarchs are less clear. Here, we compile 135,000 monarch observations between 1993-2018 from the North American Butterfly Association’s annual butterfly count to examine spatiotemporal patterns and potential drivers of adult monarch relative abundance trends across the entire breeding range in eastern and western North America. While the data revealed declines at some sites, particularly the US Northeast and parts of the Midwest, numbers in other areas, notably the US Southeast and Northwest, were unchanged or increasing, yielding a slightly positive overall trend across the species range. Negative impacts of agricultural glyphosate use appeared to be counterbalanced by positive effects of annual temperature, particularly in the US Midwest. Overall, our results suggest that population growth in summer is compensating for losses during the winter and that changing environmental variables have offsetting effects on mortality and/or reproduction. We suggest that density-dependent reproductive compensation when lower numbers arrive each spring is currently able to maintain relatively stable breeding monarch numbers. However, we caution against complacency since accelerating climate change may bring growing threats. Our data also suggest that increases of summer monarchs in some regions, especially in the west and far south, may reflect replacement of migratory with resident populations. Nonetheless, it is perhaps reassuring that ubiquitous downward trends in summer monarch abundance are not evident.