3 years ago



altitude forests provide

altitude forests provide the microclimatic conditions that monarchs must have to survive the winter. Loss of overwintering habitat threatens the survival of the monarch because the butterflies are limited to very specific habitat areas. Because of ecological and geographical requirements, colonies are only found in densely forested sites at high elevations (~2,900–3,300 m [9,500–10,800 ft]), and they are usually restricted to arroyos near stream headwaters located on moderately steep southwest-facing slopes (Slayback et al. 2007, p. 28). The cool temperature and moisture inside the oyamel forests maintain the butterflies in a state of reproductive diapause and allow them to conserve lipid reserves that fuel the wintering period and the spring remigration north (Brower et al. 2011, p. 28). The benefits that the dense canopy provide to monarchs have been likened to an umbrella, a blanket, and a hot-water bottle, protecting the butterflies from rain and keeping them warm enough not to freeze but cool enough that diapause is not broken which would deplete lipid reserves (Ibid.). The monarch’s overwintering habitat in Mexico is threatened by illegal and legal logging, water diversion, forest disease, and forest senescence. The habitat is also threatened by climate change and severe weather events, which are discussed further in the petition section on Other Factors Affecting the Species’ Continued Existence. The overwintering monarch colonies in Mexico were discovered in 1975 (Brower 1995). In 1980 a reserve was established for monarch protection, but exact protected locations were not specified, and logging was only restricted during winter months when monarchs were on site. A presidential decree in 1986 established the Monarch Butterfly Special Biosphere Reserve which protected five isolated areas in Mexico State and Michoacán comprising 16,110 ha, including 4,491 ha of core zone where all extractive activities were prohibited, and 11,619 ha of buffer zone where extractive activities were permitted if they were deemed sustainable. Forest loss and degradation continued after the establishment of the 1986 reserve. The reserve did not protect all important overwintering sites, failed to compensate local landowners for imposed restrictions, offered no effective economic alternatives to subsistence uses including logging and agriculture, and angered indigenous communities who then set forest fires in protest (Solensky 2004b, p. 118, Vidal et al. 2013, p. 178). Based on aerial photographic comparisons of forest cover, between 1971 and 1999, the size of the largest patch of high quality forest was reduced by 75 percent, and 44 percent of forest patches with greater than 80 percent cover were degraded (Brower et al. 2002). The annual rate of degradation from 1971 to 1984 was 1.70 percent and increased to 2.41 percent from 1984 to 1999 (Brower et al. 2002). In 2000 the current Monarch Butterfly Biosphere Reserve (Reserva de la Biosfera Mariposa Monarca) was established, linking the five areas from the 1986 decree and protecting 56,259 ha of forest including 13,552 ha in three core zones and 42,707 ha in two buffer zones (Vidal et al. 2013, p. 178). Even though the habitat has been under some form of protected status since 1980, logging is known to have eliminated considerable habitat for the monarchs. On the 12 known massifs that host butterfly colonies, illegal logging has eliminated overwintering habitats on several and severely degraded habitat on others. Logging has eliminated colony areas including several on the north face of Cerro Pelon and at least three areas in Lomas de Aparacio on the southern Monarch ESA Petition 68

portion of Sierra Campanario. Logging has severely degraded colony areas including the west face of Cerro Pelon and the south face of Cerro Altamirano (Brower et al. 2012a, p. 97). As recently as 2008, a small overwintering colony was documented to have been lost due to logging on the property of Crescencio Morales (Vidal et al. 2013, p. 183). Incremental logging has degraded habitat even in the two principal ecotourism colony areas, Rosario and the Sierra Chincua (Brower et al. 2012a, p. 97). Due to increased enforcement efforts and economic support, large-scale logging has mostly been curtailed in the monarch reserve since 2007, but forest loss and degradation resulting from smallscale logging, forest diseases, water diversion, severe weather events, climate change, and edge effects continue to threaten the monarch’s overwintering habitat. Vidal et al. (2013) used aerial photographs, satellite images, and field surveys to monitor forest cover in the core zones of the Reserve from 2001 to 2012. They found that from 2001-2012, 1,254 ha were deforested (defined as areas with less than ten percent canopy cover remaining), 925 ha were degraded (defined as areas in which canopy forest decreased), and 122 ha were negatively affected by climatic conditions including winds, drought, fire, and floods (p. 180). Of the total 2,179 ha of affected area, 2,057 ha were affected by illegal logging, 1,503 ha of which were affected by large-scale logging and 554 ha of which were affected by small-scale logging. They found that Mexican authorities were effectively enforcing efforts to protect the monarch reserve, particularly from 2007 to 2012, and that together with financial support to create local alternative income generation and employment, large-scale illegal logging had decreased from 731 ha affected in 2005–2007 to none affected by large-scale logging in 2012. Small-scale logging, however, remains a present and growing concern (Vidal et al. 2013, p. 177). Small-scale illegal logging for subsistence represents more than one-fourth of the total forest area that was lost and degraded from 2001-2012, and has severely affected the monarch core zones (Vidal et al. 2013, p. 183). Illegally logged wood is used mainly for local housing construction and firewood, and is primarily sold locally as the primary source of fuel in villages that lack electricity (Vidal et al. 2013, p. 184). As of 2010 approximately 27,000 people lived in 93 agrarian communities within the reserve’s buffer zones, and more than one million people live around the reserve. The economy of the monarch butterfly region faces serious economic challenges which catalyze illegal logging as a short-term option to cope with poverty (Vidal et al. 2013, p. 184). The monarch’s winter habitat is threatened by degradation from edge effects from forest loss in the buffer zones and in surrounding habitats. The forests in the buffer zones have been, and continue to be, significantly degraded by logging, grazing, fires, and agricultural expansion. Habitat degradation in the buffer zones also harms habitat in the core zones due to edge effects and climatic effects (Vidal et al. 2013, p. 184). Even small openings in the forest canopy can cause a lessening in temperature buffering effects that protect the microhabitat conditions monarchs require to remain at the correct temperatures for diapause. Opening of the forest canopy increases the daily temperature range at all heights in the forest, which can directly affect monarch physiology. Denser forest provides more optimal Monarch ESA Petition 69

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