Archive for April, 2009

Essentially no conservation attention has been paid to the monarch butterfly and its migration in the Great Basin, Mojave, and Sonoran Deserts.  A small concerted effort to understand monarch migration through southern Arizona is underway thanks to a small group of devoted citizens, yet there remains an enormous void of the monarch’s use of migration corridors and resources, and how the compounding effects of the western water crisis and climate change will impact the monarch’s migration in the western USA.

To understand the potential collective impacts on the monarch’s use of the Great Basin, Mojave, and Sonoran Deserts, it is important to first understand a little history of these deserts.  First, the Holocene Era (ca. 12,000 ybp till now) was marked with numerous wet and dry periods that undoubtedly affected the distribution of riparian areas and wet meadows, and hence milkweeds that the monarchs solely rely on for a larval food source. Given that milkweeds require relatively moist areas to grow, it is plausible that milkweed distribution expanded during wet periods and retracted during dry periods.

Second, it is important to understand the trajectory that climatic patterns in the western US are headed. Scientists with the National Research Council have reported that a significant warming trend has occurred in the West over the last century, and it is continuing. In fact, these climate scientists tell us that temperatures are expected to rise with earlier snow melts and greater evaporation rates. This impending water crisis in West likely will not result in water conservation for species that we don’t know about or have conservation concern for, but the water crisis will undoubtedly cause water-grabs for continued urban growth and development, as we’ve seen already in the West. Thus, we will see a continued retraction of riparian areas, wet meadows, and milkweed distribution in the western USA.

Third, land uses in these deserts since 1850 has been that of riparian and wet meadow loss and degredation.  In the Great Basin, 75% of riparian areas and other wet areas have been severely degraded and over half of all wetlands in the Great Basin have been completely eliminated in the last 150 years.  The situation in the Mojave and Sonoran Deserts are as equally bleak and disturbing. Moreover, milkweeds in the West are considered toxic to livestock, despite that livestock rarely if ever eat them, and so farmers, ranchers and public land agencies have been encouraged to eliminate those plants. What does this suggest has happened to the distribution of milkweeds and monarchs in these desert regions? …Further retraction of milkweeds and further decline of monarch habitat.

Why are these three points about monarchs in the western US important for conservation action and policy right now?  The importance hinges on how conservation is often done, and that is via crises. For example, the preservation a portion of monarchs overwintering sites in Mexico were rather quickly protected largely because we could easily see the vast damage that extensive logging had on the monarchs overwintering areas.  So with the enormous overwintering populations that grabbed attention and with relatively easy documentation of such losses from scientific and news publications, conservation groups, the public, and governments responded.  The situation in the western deserts is not so straightforward, despite the potential importance of these desert regions in providing resources for the continued monarch migration in the West. For one, it is difficult to estimate the historical abundances, distributions, and migrations of monarchs. 150 years ago in the western US, it is entirely plausible that milkweeds and monarchs were much more abundant and widespread than they are today. Second, if mass movements of monarchs are not seen and impending doom is not in crisis mode, it is difficult to get conservation groups, the public,  governments, and even scientists interested in working toward conservation solutions.  If monarch conservation in these desert regions continues to be ignored, one thing is for certain:  the continued warming trend, reduced waters, and the water crisis will all collectively drive monarch migrations through these deserts to extinction. That is the trajectory we are on, but it doesn’t mean we have to stay on that trajectory.