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The migration pattern of the eastern monarch butterfly (Danaus plexippus) consists of a sequence of generations of butterflies that originate in Mexico each spring, travel as far north as Southern Canada, and ultimately return to the original location in Mexico the following fall. Estimates of monarch populations in the Oyamel firs in Mexico have caused concern within the scientific community about the long-term stability of this phenomenon. We use periodic population matrices to model the life cycle of the eastern monarch butterfly and find that, under this linear model, this migration is not currently at risk. We extend the model to address the three primary obstacles for the long-term survival of this migratory pattern: deforestation in Mexico, increased extreme weather patterns, and milkweed decline. Incorporating these obstacles into the model shows that there is a definite need to take action to alleviate the aforementioned obstacles. K E Y W O R D SDanaus plexippus, mathematical model, monarch butterfly, periodic matrix population model Natural Resource Modeling. 2017;e12123.wileyonlinelibrary.com/journal/nrm

INTRODUCTION: Enhanced Recovery After Surgery (ERAS) programs are evidence-based care pathways that focus on optimizing pain control, nutrition, fluids, and mobility. We evaluated implementation of a multi-faceted ERAS program among a cesarean section surgical population within Kaiser Permanente Northern California (KPNC), an integrated healthcare delivery system. We compared process measures before and after ERAS implementation at two pilot hospitals. METHODS: We evaluated changes in perioperative pain management (morphine equivalents and multimodal analgesics), mobility (early ambulation within 12 hours) and nutrition (early feeding within 12 hours), from pre-Implementation (March 2015-August 2015, n=1390 cesarean patients) to post-Implementation (March 2016-August 2016, n=1471 cesarean patients) of the multifaceted ERAS program. All urgent and elective cases were included. We quantified these metrics based on medication administration records, preoperative checklists, and/or nursing shift assessments recorded in the EMR. RESULTS: Process metrics among ERAS patients demonstrated significant changes between pre- and post-Implementation phases. The rate of early ambulation increased from 33% to 51% (p<0.001), early postoperative resumption of nutrition increased from 17% to 57% (p<0.001), and opioid consumption decreased significantly from 13.1 mg morphine equivalents to 7.7 mg (p<0.001), while the use of multimodal analgesics increased from 5% to 87% (p<0.001). CONCLUSION: ERAS program implementation successfully altered the process-of-care metrics for cesarean section surgical patients across two pilot hospitals. Further research is needed to determine the impact of ERAS implementation on complications and other outcomes following surgery among women undergoing cesarean sections.