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monarch-esa-petition-final_61585

monarch-esa-petition-final_61585

habitat than thinned

habitat than thinned forest and provides important temperature buffering effects, especially during severe weather events (Brower et al. 2011, p. 27, 42). The integrity of the high-elevation cloud forest that supports the monarchs depends upon an extensive and dense forest structure to capture moisture (Brooks et al. 1997). Ongoing logging and canopy loss threatens to undermine the hydrological integrity of the ecosystem, which threatens the continued survival of the overwintering monarchs (Calvert et al. 1979, Slayback et al. 2007, p. 39). Small canopy openings also increase edge effects which increase the risks of wildfire, tree mortality, changes in plant and animal species, and increased human use of the land (Vidal et al. 2013, p. 8). In addition to small-scale logging, the monarch’s overwintering forest habitat is threatened by senescence and forest diseases. There has been a recent increase in the level of bark-beetleinduced tree mortality in the overwintering grounds. Several species of beetles are causing tree mortality including Scolytus mundus Wood, Psuedohylesinus variegatus [Blandford], Pityopthorus spp., and Dendroctonus mexicanus Hopkins (Steed and Willhite 2011, p. 12). Most tree mortality in the core area is in oyamel firs that have been attacked by P. variegatus, which was “observed in the lower bole of every examined dead and dying fir greater than 5 inches in diameter at breast height” during a recent forest health assessment (Steed and Willhite 2011, p. 3). Although only a small area has been affected, the beetle outbreak is occurring in multiple sites within the reserve. In an attempt to stop the spread of the beetle, 9,000 trees were felled in 2009 alone. It is estimated that 15 years of continued beetle population growth could decimate the fir trees in the reserve (COSEWIC 2010, p. 12). Other disease agents are also contributing to increased levels of mortality of firs, pines, and other trees in the reserve including annosus root disease (Heterobasidion annosum, P-group [now H. occidentale]) and dwarf mistletoes (Arceuthobium abietis-religiosae Heil, A. globosum Hawksw. and Wiens) (Steed and Willhite 2011, p. 12). In field visits from 2011-2012, Vidal et al. (2013) identified 14 ha of forest that had been impacted by drought and parasitic plants (Arceuthobium spp. and Psittacanthus calyculatus) and an additional 7 ha that had been logged for disease control (p. 181). In addition to tree loss due to disease and disease-control activities, natural forest aging also threatens the reserve because monarchs typically form colonies in mature forests and as forest patches age, it is unclear whether they will be replaced (Keiman and Franco 2004). Water diversion for human and domestic animal use may also pose a significant threat to overwintering habitat in Mexico (Commission for Environmental Cooperation 2008). At one major water source for monarchs—the Ojo de Aqua ravine on the south side of Cerro Pelόn—water has been diverted so extensively that the stream is now dry for more than 1 km. Monarchs now have to fly farther distances to obtain water, which may deplete the lipid reserves needed to survive the winter and sustain the spring migration (Ibid). As discussed in more detail in the Other Factors Affecting the Monarch’s Continued Existence Section of this petition, severe weather events threaten the monarchs with direct mortality and with habitat degradation when trees fall down due to ice, wind, fire, floods, or drought. From 2009-2011, 115 hectares of forest were impacted by floods, strong winds, droughts, and fires, Monarch ESA Petition 70

and 21 additional hectares were impacted by drought and parasitic plants in 2012 (Vidal et al. 2013, p. 182). From 2008 to 2011, the monarch reserve was affected by extreme drought which likely stressed the trees and made them more vulnerable to disease (Vidal et al. 2013, p. 182). Climate change threatens to eliminate the monarch’s current overwintering habitat. Oberhauser and Peterson (2003) used ecological niche modeling to identify areas suitable for overwintering monarch colonies under both current and future climate scenarios. The models predicted current monarch presence with a high degree of accuracy, and indicated that precipitation and diurnal temperature range are key environmental factors in making locations suitable for monarchs. The models predicted that future conditions are likely to become unsuitable across the entire current winter range, particularly owing to increased cool-weather precipitation that could cause increased mortality events (Oberhauser and Peterson 2003, p. 14063). Saenz-Romero et al. (2012) likewise found that the forests which currently support monarchs are likely to become unsuitable habitat by the end of this century in the face of global climate change. They projected the contemporary climate niche into future climates provided by three General Circulation Models and found that the area occupied by the current climate niche will diminish rapidly in the next one hundred years. The models predicted a decrease in suitable climatic habitat conditions of 69.2 percent by the decade surrounding 2030, a decrease of 87.6 percent for the decade surrounding 2060, and a decrease of 96.5 percent for the decade surrounding 2090. Direly, “the projections show that by the end of the century, suitable habitat for the monarch butterfly may no longer occur inside the [Monarch] Biosphere Reserve” (Saenz- Romero et al. 2012, p. 98). Thus appropriate habitat for overwintering monarchs could be eradicated entirely within the century because the forests outside the reserve have largely been lost and degraded. Loss and Degradation of Overwintering Habitat in California In the western United States, hundreds of thousands of monarchs coalesce every fall at forested groves along the Pacific Coast. Monarchs generally begin to arrive to the California coast in mid- October (Hill et al. 1976) but may arrive as early as September (Leong 1990). These groves have historically been distributed as far north as Mendocino County, and south into Baja California, although the monarch’s overwintering range has contracted in recent years (Griffiths and Villablanca unpublished data), and monarchs are rarely found overwintering in the far northern and southern extremes of their overwintering range. Similar to the monarchs that overwinter in Mexico, monarchs return to many of the same locations in California year after year. There are 458 distinct locations where overwintering monarchs have clustered, although currently only about 30 sites host more 1,000 monarchs annually (Xerces Monarch Overwintering Database 2014). Historically, the composition of vegetation on the California coast differed from the contemporary composition, and groves of native trees presumably hosted dense monarch aggregations in the past (Lane 1984, 1993). At present, most overwintering sites in California are dominated by nonnative blue gum (Eucalyptus globulus) or red river gum (E. camaldulensis), although many sites also contain native trees such as Monterey pine (Pinus radiata), Monterey cypress (Cupressus macrocarpa), western sycamore (Platanus racemosa), coast redwood Monarch ESA Petition 71

MONARCH CONSERVATION
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