Will the Monarch Overwintering Sites Survive Climate Change?

by Cuauhtémoc Sáenz-Romero and Roberto Lindig-Cisneros

Sacred Abies( religiosa), often Averaging several climatic models and called oyamel, is a large , greenhouse-effect gas emission scenarios, whose dense, dark-green beautiful crown we have projected that, in , there will resembles that of Douglas-fir. Sacred are be a temperature increase of 6.7° F and a found only in high altitude sites (from about precipitation decrease of 18.2 % by the end Monarch 8,000 to about 12,000 ft.) in Mexico, mostly of the century. That will mean more heat and Biosphere Iztaccíhuatl along the Trans-Mexican Volcanic Belt, a drought stress for the . More stress means Reserve Popocatépetl formation that includes the majestic and that the trees will have less natural defenses snow-covered Popocatépetl and Iztaccíhuatl to prevent attacks of insects and diseases; and volcanoes. more successful attacks means that more trees Eastern migratory Monarchs spend will become unhealthy and then die. Massive Map of central Mexico showing the location of the Monarch Biosphere Reserve and of the winter amidst the dense and mature climate-change related deaths of trees have the volcanoes Iztaccíhuatl and Popocatépetl. populations of sacred firs located within the been documented in many parts of the world Monarch Biosphere Reserve (MBR) located recently: e.g., Pinyon Pine in the southwestern at the borders of the Mexican states of United States and Quaking Aspen in the indicating areas where the current climate single square mile of climate suitable for Michoacán and México (see map, page 15). Rocky Mountains of the U.S. and Canada. is suitable for sacred firs, even if sacred firs sacred firs within the MBR (no red pixels Here, the take advantage of Our concern is that forest decline due are not actually there. Finally, we repeated inside the MBR area on the map of pg. 16; 2 the umbrella and blanket effects of the sacred to climatic change eventually will affect the the mapping process, but now used climate each pixel ~ 0.4 mile ). We call this process fir forest canopy and branches, packing sacred fir forest inside the MBR. The near projections for the decades centered in years a decoupling between the tree populations together in colonies where butterflies cluster exclusive use of these trees as Monarch winter 2030, 2060 and 2090. and the climate for which they are adapted. side-by-side on the stems and branches to roosts makes it difficult to envision survival The results of this research project that The tree populations stay, but the appropriate prevent mortality during cold and rainy winter of overwintering butterflies at this site without the climate suitable for sacred firs will occupy climate moves away, climbing the mountains, nights. It is clear that, if we want to protect the trees. Increasingly, observers see sacred an area that shrinks as time passes, ascending to higher altitudes. The trees left behind by the the migratory Monarchs, we must protect the firs inside the MBR that exhibit signs of die- in altitude. For example, the contemporary moving climate then start suffering the stresses sacred fir populations inside the MBR. back, apparently due to drought stress in the climate allows growth of healthy sacred imposed by a new warmer and dryer climate, Generation after generation of Monarchs changing climate (see top right photo, pg. 17). firs that now are found at about 9,842 ft. in become debilitated and more easily subject have overwintered in the sacred fir forests We developed a mathematical model that elevation but the same climate will occur at to the attacks of insects and diseases, and now protected inside the MBR. Amazingly, allows us to predict the geographic distribution 10,827 ft. in 2030. In other words, the climate eventually they die. the Monarch generation that arrives at the of the climate suitable for sacred firs, and will move about 1000 ft. upward by 2030. The Can sacred fir populations “fix” the MBR has never been there before. Somehow then project where that climate will be in the problem is that at higher and higher altitudes, problem by themselves, moving, by natural the information required to navigate from future (decades centered in years 2030, 2060 the mountains have less and less surface area, means, altitudinally upwards and keeping pace Canada and the United States to the MBR and 2090). We did that by comparing the until we finally reach the mountain summit. with the moving appropriate climate? The is genetically passed from one generation to contemporary climate (averaging 30 years, At that point, there is no more land available answer plainly is no. The natural migration the next. This incredible natural phenomenon from 1961 to 1990) at the sites where there with a climate suitable for sacred firs (see processes of sacred firs, depending upon wind might make it difficult for Monarchs to adapt is natural distribution of sacred firs, with the map, page 16). dispersal of , establishing new seedlings to the effects of global climatic change. climate at sites where sacred firs are absent. It is extremely troubling that, by year that then grow until they reach sexual Then, we used GIS software to construct maps 2090, we project that there will not be a maturity, and reproduce again to release a new 14 American Butterflies,Summer 2012 15