Milkweed loss in agricultural fields because of herbicide use: effect on the monarch butterfly population

1. The size of the Mexican overwintering population of monarch butterflieshas decreased over the last decade. Approximately half of these butterflies comefrom the U.S. Midwest where larvae feed on common milkweed. There has been alarge decline in milkweed in agricultural fields in the Midwest over the last decade.This loss is coincident with the increased use of glyphosate herbicide in conjunctionwith increased planting of genetically modified (GM) glyphosate-tolerant corn(maize) and soybeans (soya).2. We investigate whether the decline in the size of the overwintering populationcan be attributed to a decline in monarch production owing to a loss of milkweeds inagricultural fields in the Midwest. We estimate Midwest annual monarch productionusing data on the number of monarch eggs per milkweed plant for milkweeds in differenthabitats, the density of milkweeds in different habitats, and the area occupiedby those habitats on the landscape.3. We estimate that there has been a 58% decline in milkweeds on the Midwestlandscape and an 81% decline in monarch production in the Midwest from 1999 to2010. Monarch production in the Midwest each year was positively correlated withthe size of the subsequent overwintering population in Mexico. Taken together, theseresults strongly suggest that a loss of agricultural milkweeds is a major contributorto the decline in the monarch population.4. The smaller monarch population size that has become the norm will make thespecies more vulnerable to other conservation threats.

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Monarch butterfly and milkweed declines substantially predate the use of genetically modified crops

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1811437116 ◽

2019 ◽

Vol 116 (8) ◽

pp. 3006-3011 ◽

Cited By ~ 20

Author(s):

J. H. Boyle ◽

H. J. Dalgleish ◽

J. R. Puzey

Keyword(s):

Genetically Modified ◽

Danaus Plexippus ◽

Genetically Modified Crops ◽

Monarch Butterfly ◽

The United States ◽

Gm Crops ◽

Herbicide Resistant ◽

The Past ◽

Scientific Attention ◽

Herbicide Use

Monarch butterfly (Danaus plexippus) decline over the past 25 years has received considerable public and scientific attention, in large part because its decline, and that of its milkweed (Asclepias spp.) host plant, have been linked to genetically modified (GM) crops and associated herbicide use. Here, we use museum and herbaria specimens to extend our knowledge of the dynamics of both monarchs and milkweeds in the United States to more than a century, from 1900 to 2016. We show that both monarchs and milkweeds increased during the early 20th century and that recent declines are actually part of a much longer-term decline in both monarchs and milkweed beginning around 1950. Herbicide-resistant crops, therefore, are clearly not the only culprit and, likely, not even the primary culprit: Not only did monarch and milkweed declines begin decades before GM crops were introduced, but other variables, particularly a decline in the number of farms, predict common milkweed trends more strongly over the period studied here.

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A trans-national monarch butterfly population model and implications for regional conservation priorities

Ecological Entomology ◽

10.1111/een.12351 ◽

2016 ◽

Vol 42 (1) ◽

pp. 51-60 ◽

Cited By ~ 65

Author(s):

KAREN OBERHAUSER ◽

RUSCENA WIEDERHOLT ◽

JAY E. DIFFENDORFER ◽

DARIUS SEMMENS ◽

LESLIE RIES ◽

...

Keyword(s):

Population Model ◽

Monarch Butterfly ◽

Conservation Priorities ◽

Butterfly Population ◽

Regional Conservation

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Monarch butterfly population dwindling

Physics Today ◽

10.1063/pt.5.027664 ◽

2014 ◽

Keyword(s):

Monarch Butterfly ◽

Butterfly Population

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Characterizing New Wintering Sites for Monarch Butterfly Colonies in Sierra Nevada, Mexico

Insects ◽

10.3390/insects11060384 ◽

2020 ◽

Vol 11 (6) ◽

pp. 384

Author(s):

Ramiro Pérez-Miranda ◽

Víctor Javier Arriola-Padilla ◽

Martín Enrique Romero-Sanchez

Keyword(s):

Climate Change ◽

Protected Areas ◽

Sierra Nevada ◽

Danaus Plexippus ◽

Monarch Butterfly ◽

Field Trips ◽

Conservation Strategies ◽

National Commission ◽

Butterfly Population

Every year, Danaus plexippus (Linnaeus, 1758) travels to hibernate in oyamel fir forests located between the limits of the states of Michoacán and Mexico in Mexico. Climate change and anthropogenic actions are diminishing oyamel fir forests in Mexico, putting pressure on the habitats of monarch butterflies. In the last decade, new colonies outside their usual range have been predicted through modeling and reported by the National Commission on Protected Areas of Mexico. The objectives of the study were to recover information on the historical and new hibernation sites, reported or modeled, from different literature sources. We also aimed to perform a bioclimatic and forest biometric characterization of new monarch butterfly colonies located in Sierra Nevada in Mexico to provide information to aid in conservation strategies for the monarch butterfly population. We conducted field trips to georeference the colonies at sites located in the Atlautla municipality in Mexico State. Climatic, topographic, and forest biometric variables were used to characterize the sites physically. It was found that the butterfly’s roosts occurred at a higher elevation than those recorded by other sources. The locations where the monarch’s colonies were established, in the east of Mexico State, provide information relevant to defining and developing policies for their conservation.

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Monarch butterfly and milkweed declines substantially predate the use of genetically modified crops

10.1101/378299 ◽

2018 ◽

Cited By ~ 2

Author(s):

JH Boyle ◽

HJ Dalgleish ◽

JR Puzey

Keyword(s):

Genetically Modified ◽

Danaus Plexippus ◽

Genetically Modified Crops ◽

Monarch Butterfly ◽

The United States ◽

Gm Crops ◽

Herbicide Resistant ◽

The Past ◽

Scientific Attention ◽

Herbicide Use

AbstractMonarch butterfly (Danaus plexippus) decline over the past 25 years has received considerable public and scientific attention, in large part because its decline, and that of its milkweed (Asclepias spp.) host plant, have been linked to genetically modified (GM) crops and the associated herbicide use. Therefore, the monarch has emerged as a poster child for the anti-GM movement. Here we use museum and herbaria specimens to extend our knowledge of the dynamics of both monarchs and milkweeds in the United States to more than a century, from 1900-2016. We show that monarch population trends closely follow those of their milkweed hosts; that both monarchs and milkweeds increased during the early 20th century, and that recent declines are actually part of a much longer term decline in both monarchs and milkweed beginning around 1950. Herbicide resistant crops, therefore, are clearly not the only culprit, and likely not even the primary culprit, as these declines began decades before GM crops were introduced.

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Effects of human activities on monarch butterfly habitat in protected mountain forests, Mexico

The Forestry Chronicle ◽

10.5558/tfc79242-2 ◽

2003 ◽

Vol 79 (2) ◽

pp. 242-246 ◽

Cited By ~ 18

Author(s):

M Isabel Ramírez ◽

Joaquín G Azcárate ◽

Laura Luna

Keyword(s):

Protected Areas ◽

Human Activities ◽

Forest Disturbance ◽

Monarch Butterfly ◽

Subsistence Farming ◽

Mountain Forests ◽

Recovery Processes ◽

Wood Extraction ◽

Disturbance And Recovery ◽

Butterfly Population

Since the monarch butterfly overwintering habitat was discovered in the mountainous fir forests in central Mexico three presidential decrees have been issued (1980, 1986, 2001) to protect it. But these forests are the source of livelihood for many local people, whose activities (wood extraction and clearance for subsistence farming) represent a major threat to the forests, and thus to the butterfly population. This study identifies important deforestation, disturbance, and recovery processes caused by human activities in the protected areas and their surroundings. Contrary to our expectations, the protected areas have been most negatively affected by human activities, whereas areas devoted to multiple uses have been more adequately preserved. Key words: monarch butterfly habitat, deforestation, forest disturbance, protected areas

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