It is true that milkweed reduction due to increased herbicide use in the Midwest has facilitated massive reduction in monarch butterflies’ population ( Pleasants & Oberhauser, 2013) . Monarch butterflies are attracted to Midwestern plains and habitats during the fall and winter seasons where milkweeds thrive through a unique chemical signaling phenomenon. Glyphosate herbicides are attributed to controlling milkweed population in farms where the weed threatens crops and ultimately reduces production. This has destroyed both agricultural and non-agricultural habitats altering developmental processes of monarch butterflies leading to 81% decline in population during the last decade (1999-2010). Reproductive processes such as egg-laying and hatching are also affected as there are fewer patch sizes to accommodate females in agricultural and non-agricultural habitats.
According to Hopwood et al. (2012) , monarch larvae feed exclusively on milkweed species which drives the annual migration to Central Mexico leading to overwintering. The article attributes decline in population to three major factors: loss of milkweed habitats, logging at overwintering zones and climate change. Milkweed being the primary food source, has threatened agricultural practices and production leading to increased herbicide use on milkweed and pesticides on monarchs. Increased wood harvesting practices such as illegal logging have damaged forests and other riparian habitats therefore damaging developmental stages and disrupting wintering. Lastly, climate change has increased vulnerability to extreme weather which promotes diseases and predation.
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A similar example involves neonicotinoid chemicals and their influence on bees’ population. Due to their extreme chemical ability and lifespan, neonicotinoids are easily absorbed by plants causing bioaccumulation and incorporation into pollen and nectar. This results to direct interaction with bees especially during pollination leading to poisoning of colonies. North America, particularly Midwestern states which produce corn and soybeans have diversifies to genetically modified crops which are repulsive to monarch butterflies and integrate vast agricultural chemicals to increase production which has resulted to a 21% decline of monarchs in agricultural habitats ( Jepsen et al., 2015) . Therefore, enhancing research in both agricultural and non-agricultural habitats to effectively understand dynamics of migration, breeding and reproduction, development and chemical influence on monarch population is necessitated to broaden knowledge and potentiate conservation.
References
Pleasants, J. M., & Oberhauser, K. S. (2013). Milkweed loss in agricultural fields because of herbicide use: effect on the monarch butterfly population. Insect Conservation and Diversity , 6 (2), 135-144.
Hopwood, J., Vaughan, M., Shepherd, M., Biddinger, D., Mader, E., Black, S. H., & Mazzacano, C. (2012). Are neonicotinoids killing bees. A review of research into the effects of neonicotinoid insecticides on bees, with recommendations for action. Xerces Society for Invertebrate Conservation, USA .
Jepsen, S., Schweitzer, D. F., Young, B., Sears, N., Ormes, M., & Black, S. H. (2015). Conservation status and ecology of the monarch butterfly in the United States . NatureServe.
