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monarch-esa-petition-final_61585

monarch-esa-petition-final_61585

supporting materials, p.

supporting materials, p. 30). The model is based on the assumption that increasing temperatures from climate change will decrease the risk of severe winter storm events, yet this assumption is not supported by other climate models. The model also fails to take into account the influence of predicted warmer temperatures on lipid depletion during overwintering which reduces butterfly fitness (See Threats…Other Factors, Global Climate Change). Thus, the Flockhart et al. (2014) model demonstrates that the monarch is threatened, yet certainly still underestimates extinction risk. The model demonstrates that ongoing population declines will be driven by land-use change and global climate change, and identifies as a top priority for slowing future population declines the need to reduce the loss of milkweed host plants in the Midwest and Southern U.S. breeding grounds, which they determine is the primary driving force behind the current population decline (p. 3, 14). The model also demonstrates that the drastically reduced current population size of monarchs makes the species even more vulnerable to catastrophic events. The overall population of monarchs in North America is exhibiting a significant decline and the butterflies are facing high magnitude, imminent threats from multiple factors across their range. THE MONARCH BUTTERFLY WARRANTS ESA PROTECTION The Endangered Species Act states that a species shall be determined to be endangered or threatened based on any one of five factors (16 U.S.C. § 1533 (a)(1)). In this case, the monarch is threatened by all five of these factors and warrants protection under the Act. The monarch is threatened by the first factor, the modification and curtailment of habitat and range, due to the drastic reduction of milkweed in its summer breeding habitat that has occurred due to increased herbicide spraying caused by the widespread adoption of genetically-engineered, herbicideresistant corn and soybean crops (Pleasants and Oberhauser 2012, Flockhart et al. 2014). Monarch habitat has also been reduced due to increased production of ethanol since 2007 that has resulted in conversion of grasslands to corn and eliminated milkweed from those habitats (Brower et al. 2012a), and by other factors such as urban development and aggressive management of roadside vegetation (Commission on Environmental Cooperation 2008). East of the Rockies, it has been very roughly estimated that approximately 167 million acres of monarch habitat, an area about the size of Texas, may have been lost since the mid-1990s due to agricultural changes and development, including nearly one-third of the monarch’s total summer breeding range (Taylor 2014). The monarch’s wintering grounds are threatened by illegal logging, legal wood gathering, water diversion, and agricultural conversion of forest land in Mexico, and by development, aging forests, and other threats in California. The butterfly is potentially threatened by the second factor, overutilization, due to commercial production and release of large numbers of butterflies, which threatens to spread disease and undesirable genetic traits to wild populations. The monarch is also threatened by the third factor, disease or predation. High levels of predation are a significant threat at all life stages, especially in synergy with habitat loss and declining populations. Disease further threatens the monarch, and the spread of one protozoan parasite in particular may be reducing the proportion of females in the population and thus reducing the monarch’s potential for population growth and recovery (Davis and Rendón-Salinas 2010). The fourth factor, inadequacy of existing regulatory mechanisms, is a threat because voluntary efforts undertaken have not been able to stop and reverse population decline. Finally, monarchs are also threatened by the fifth factor, other natural and manmade factors affecting their continued existence, including pesticides, invasive species, global climate Monarch ESA Petition 44

change, and stochastic weather events. Severe weather conditions have been identified as one of the primary factors in the recent precipitous decline in monarch numbers (Brower et al. 2012a,b). Synergies between all of these factors magnify the intensity of threats facing monarchs. Climate change, for example, will exacerbate other threat factors such as disease and habitat loss, and habitat loss will increase threats from other factors including disease and predation. There are no existing regulatory mechanisms that are adequate to protect the monarch butterfly from all of these threat factors. As discussed in detail in the Significant Portion of Range section of this petition, below, the monarch is at risk of extinction in a significant portion of its range in North America because without the significant North American population, the redundancy, resiliency, and representation of the species would be so impaired that the monarch would have an increased vulnerability to threats to the point that the overall species would be likely to become endangered in the foreseeable future. The monarch butterfly needs ESA protection as a threatened species to address landscape level threats to its existence before its population declines to the level of endangerment. THREATS FACTOR ONE: MODIFICATION OR CURTAILMENT OF HABITAT OR RANGE Monarch Habitat Loss Due to Pesticides The monarch butterfly is threatened by modification and curtailment of habitat and range due to the drastic loss of milkweeds, especially common milkweed (Asclepias syriaca L.), caused by increased and later-season use of the herbicide glyphosate. Glyphosate use has increased dramatically because of the widespread planting of genetically-engineered, herbicide-resistant corn and soybeans in the Corn Belt region of the United States and to planting of geneticallyengineered cotton in the southern United States and California. In the Midwest, nearly ubiquitous commercial planting of, glyphosate-resistant Roundup Ready corn and soybeans has caused a precipitous decline of common milkweed, and thus of monarchs, which lay their eggs only on milkweeds. Moreover, milkweed from crop fields is particularly significant for maintaining monarch abundance (Oberhauser et al. 2001, Pleasants and Oberhauser 2012, Flockhart et al. 2014). On top of the loss of milkweed in crop fields, much habitat that once hosted milkweed, particularly Conservation Reserve Program land, has recently been converted to geneticallyengineered, glyphosate-resistant corn and soybeans to produce biofuels. In addition, new multiple genetically-engineered, herbicide-resistant crops, soon to be introduced, will further degrade monarch habitat by reducing nectar resources for monarch adults via increased herbicide drift damage, and causing further loss of milkweed in agricultural fields. Threats posed to monarchs from pesticides in addition to habitat loss are discussed in the petition section Other Factors- Pesticides. As discussed in detail in the Natural History section of this petition, the majority of the world’s monarchs originate in the Corn Belt region of the United States, and the demographic importance of this region to the resiliency, redundancy, and representation of Danaus plexippus plexippus Monarch ESA Petition 45

MONARCH CONSERVATION
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