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Farming highland regions can impact seasonal malaria transmission by changing rainfall patterns, temperature and vegeta- tion, according to GBC Health, a coalition of businesses and other organizations seeking solutions to global health issues. Dr. Myers points to changes in Belize's lowland areas catalyzed by highland agri- culture as indicative of how indirectly the process works. "Putting fertilizer in upland agricultural areas and putting nitrogen and phosphate in downriver wetland areas will change plant composition," he says. "That's the example we have from Belize, where highland agriculture leads to lowland malaria because you actually have nutri- ent enrichment in the wetlands that has changed the plant species in a way that favors a different mosquito vector and the anopheles vector, and so they become more abundant." While vector-borne diseases may be viewed primarily as Third World prob- lems, HIV proves that epidemics are global threats. And the CDC estimates that 300,000 cases of Lyme disease are diagnosed annually in the United States. A Greater Threat The Food and Agriculture Organization of the United Nations reports that nearly 870 million people worldwide were chroni- cally undernourished between 2010 and 2012. That translates to one in eight people. The continued escalation of global popula- tion raises ominous questions about future food supplies. Dr. Myers researches how climate change affects global nutrition, and he considers the impact of that complex dynamic the largest threat to public health. "We're recognizing that we have this huge challenge of increasing food production, and we already have people who don't get enough to eat," he says. "Climate change adds a series of constraints around tempera- ture changes, precipitation, sea level rise, and change in the relationship between agricultural crops and pests and pathogens." While producing enough food is a global concern for the near future, Dr. Myers' research investigates how ecosystem change results in nutritional deficits. For example: + Rising carbon dioxide levels decrease the nutritional value of food crops. + Declining pollinators can alter local populations' vitamin A intake. + Bushmeat is a dietary staple for people living in Madagascar, and its increas- ing scarcity creates the potential for iron and zinc deficiencies. "Across the board, what we're trying to do is characterize the public health importance of these natural systems, and then quantify how changes in the state of those systems will [make] an impact," Dr. Myers says. Some researchers believe the global threats presented by dwindling food supplies will have a domino effect. For people liv ing in a rea s a lready impacted by food scarcity, the problem will worsen. Yet wealthier, industrialized nations may face equally dire consequences. Dr. Myers points to politically destabiliz- ing forces coalescing in undernourished world populations. When countries begin f ighting over fa rmla nd or access to drinking water, the endgame is anything but clear. ■ "We're more rapidly transforming … natural systems, so we're changing the playing field on which global health is taking place. As physicians, particularly public health experts, we have a responsibility to understand that that dynamic is real, and if we continue to transform our [eco] systems with impunity and without paying attention to the health dimensions, we're going to start moving backwards in terms of global health." — Samuel S. Myers, MD, MPH, research scientist in the Department of Environmental Health at Harvard School of Public Health, Clinical Instructor at Harvard Medical School 2 6 | Minnesota MD NEWS ■ M D N E W S . CO M