Multi‐season climate projections forecast declines in migratory monarch butterflies

Zylstra, Erin R.; Neupane, Naresh; Zipkin, Elise F.

doi:10.1111/gcb.16349

Cited by 11 publications

(6 citation statements)

References 78 publications

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“…These findings support conservation efforts to increase monarch population size by increasing the number of milkweeds on the landscape (Thogmartin, López‐Hoffman, et al, 2017). Buffering the population from the effects of climate change is a more difficult proposition (Zylstra et al, 2021, 2022), but increasing habitat availability across the summer breeding range could, at least for a while, provide a buffer against deleterious effects of a changing climate.…”

Section: Discussionmentioning

confidence: 99%

“…Although the majority of milkweed habitat loss occurred during the period of eradication of milkweeds from crop fields, the amount of milkweed habitat continued to be eroded by land conversion from habitat with milkweed to cropland and development (Lark et al, 2020(Lark et al, , 2022. Additionally, weather conditions associated with low monarch numbers appear to be more frequent under climate change (Zylstra et al, 2022). None of the migration surveys had a downward trend (Figure 2) except Monarch Watch tagging which showed a significant decline (Table S5).…”

Section: Discussionmentioning

confidence: 99%

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A comparison of summer, fall and winter estimates of monarch population size before and after milkweed eradication from crop fields in North America

Pleasants,

Thogmartin,

Oberhauser

et al. 2023

Insect Conserv Diversity

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Measures of the area occupied by overwintering monarchs in México since the mid‐1990s show a decline. Summer surveys of monarchs, however, do not show a similar decline. This discrepancy has led to the proposition that summer monarch numbers are actually stable and that increasing mortality during migration has led to declining overwintering numbers. A competing hypothesis is that this discrepancy is due to a sampling bias in the summer counts and that the summer population has declined because of the eradication of milkweed habitat from crop fields that occurred in the late 1990s through mid‐2000s. We posit that the sampling bias occurred during the period when milkweeds were declining in crop fields and resulted from not sampling in the crop fields. We examined three measures of the size of the population made in the fall during migration and four summer survey measures and compared them to the overwintering measures. Counts of migrating monarchs are not expected to have this sampling bias since migrants come from all habitats, including crop fields. During the period of milkweed eradication, counts of the migrating population were correlated with the size of the overwintering population, whereas summer survey counts were not. After milkweed eradication from crop fields, all population measures were correlated with one another. These results indicate that during the pre‐eradication period, summer counts were not an accurate measure of summer population size. Population trends observed at the overwintering site reflect factors, principally milkweed loss, that affect summer population size.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

A comparison of summer, fall and winter estimates of monarch population size before and after milkweed eradication from crop fields in North America

Pleasants,

Thogmartin,

Oberhauser

et al. 2023

Insect Conserv Diversity

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“…GDD, a cumulative calculation of temperature above a certain threshold (Gordon and Bootsma 1993), was used to quantify the amount of heat experienced during butterfly development during the spring of the year that specimens were collected as well as during the preceding summer when they were larvae. This approach for tracking heat available to heterothermic animals has been widely adopted to model or analyze development rate (Saunders et al 2016, Kingsolver and Buckley 2020, Zylstra et al 2022) and Cayton et al (2015) showed that GDD was a better way to track the effects of warming on butterfly phenology than any other way of quantifying heat. The main drawback using GDD is that it does not account for the retarding effects of very high temperatures on growth rate, but in our study region, such warm temperatures did not occur.…”

Section: Methodsmentioning

confidence: 99%

Wing lengths of three Arctic butterfly species decrease as summers warm in Alaska

Daly,

Sikes,

Mann

et al. 2024

Ecography

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Climate warming can cause arthropods to express plastic and/or evolved changes in morphology. Previous studies have demonstrated that body sizes of Arctic butterflies are influenced by the temperatures experienced as larvae. To investigate whether this was occurring among Alaskan butterflies, we analyzed temporal trends in the wing sizes of three Holarctic species, Colias hecla, Boloria chariclea and Boloria freija, using museum specimens collected in Arctic tundra regions of Alaska between 1971 and 1995. Wing length was compared to accumulated growing degree days (GDD) during both the spring of the year collected and the previous year's summer during the normal period of larval development. We used mixed‐effects models to test if spring and summer temperatures affected adult morphology. Results show that for every 1°C increase in average seasonal temperature, wingspans decreased between 0.7 and 5 mm, with B. freija the most strongly affected. Our results suggest that the morphological sensitivity of Arctic butterflies to warming is the outcome of interactions between life‐history traits and regional climate, with all species sensitive to warming the summer before the flight year as well as warming the spring of the flight year. Boloria freija, which overwinters as late instar larvae that do not feed before pupation the following spring, was particularly strongly affected by summer warming.

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“…With spring conditions potentially becoming less favourable for monarch recruitment (Neupane et al., 2022; Zylstra et al., 2022), a deeper understanding of the direct links between local weather conditions and monarch abundance can aid management and policy decisions for eastern monarchs, a population of substantial conservation concern. Fortunately, multiple volunteer data‐collection networks compile opportunistic observations of adult monarchs in the spring and early summer.…”

Section: Methodsmentioning

confidence: 99%

“…Migratory species offer many ecosystem services that are highly valued by humans including nutrient cycling, pest control, seed dispersal, recreational opportunities, and food (Green & Elmberg, 2014; Mattsson et al., 2018; Thogmartin et al., 2022). Across taxonomic groups, migratory species have declined and face ongoing threats from myriad factors including climate change and habitat loss (Deinet et al., 2020; Zurell et al., 2018; Zylstra et al., 2022). Migratory species are among the most vulnerable species groups because they traverse large geographic areas throughout their annual cycle, making them susceptible to stressors across wide geographic regions including breeding grounds, nonbreeding grounds and throughout migratory pathways (Saunders et al., 2021; Zylstra et al., 2021).…”

Section: Introductionmentioning

confidence: 99%

Overcoming data gaps using integrated models to estimate migratory species' dynamics during cryptic periods of the annual cycle

Farr,

Zylstra,

Ries

et al. 2024

Methods Ecol Evol

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Environmental and anthropogenic factors affect the population dynamics of migratory species throughout their annual cycles. However, identifying the spatiotemporal drivers of migratory species' abundances is difficult because of extensive gaps in monitoring data. The collection of unstructured opportunistic data by volunteer (citizen science) networks provides a solution to address data gaps for locations and time periods during which structured, design‐based data are difficult or impossible to collect. To estimate population abundance and distribution at broad spatiotemporal extents, we developed an integrated model that incorporates unstructured data during time periods and spatial locations when structured data are unavailable. We validated our approach through simulations and then applied the framework to the eastern North American migratory population of monarch butterflies during their spring breeding period in eastern Texas. Spring climate conditions have been identified as a key driver of monarch population sizes during subsequent summer and winter periods. However, low monarch densities during the spring combined with very few design‐based surveys in the region have limited the ability to isolate effects of spring weather variables on monarchs. Simulation results confirmed the ability of our integrated model to accurately and precisely estimate abundance indices and the effects of covariates during locations and time periods in which structured sampling are lacking. In our case study, we combined opportunistic monarch observations during the spring migration and breeding period with structured data from the summer Midwestern breeding grounds. Our model revealed a nonstationary relationship between weather conditions and local monarch abundance during the spring, driven by spatially varying vegetation and temperature conditions. Data for widespread and migratory species are often fragmented across multiple monitoring programs, potentially requiring the use of both structured and unstructured data sources to obtain complete geographic coverage. Our integrated model can estimate population abundance at broad spatiotemporal extents despite structured data gaps during the annual cycle by leveraging opportunistic data.

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Multi‐season climate projections forecast declines in migratory monarch butterflies

Abstract: Rapid changes in the Earth's climate disrupt wildlife population dynamics in myriad ways, by shifting or contracting species' ranges

Cited by 11 publications

References 78 publications

A comparison of summer, fall and winter estimates of monarch population size before and after milkweed eradication from crop fields in North America

A comparison of summer, fall and winter estimates of monarch population size before and after milkweed eradication from crop fields in North America

Wing lengths of three Arctic butterfly species decrease as summers warm in Alaska

Overcoming data gaps using integrated models to estimate migratory species' dynamics during cryptic periods of the annual cycle

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