The Arctic continues to warm at a rate that is currently twice as fast as the global average. Warming is causing normally frozen ground (permafrost) to thaw, exposing significant quantities of organic soil carbon to decomposition by soil microbes (Romanovsky et al. 2010, Romanovsky et al. 2012). This permafrost carbon is the remnants of plants, animals, and microbes accumulated in frozen soil over hundreds to thousands of years (Schuur et al. 2008). The northern permafrost zone holds twice as much carbon as currently in the atmosphere (Schuur et al. 2015, Hugelius et al. 2014, Tarnocai et al. 2009, Zimov et al. 2006). Release of just a fraction of this frozen carbon pool, as the greenhouse gases carbon dioxide and methane, into the atmosphere would dramatically increase the rate of future global climate warming (Schuur et al. 2013).
When natural environments change, species may shift their distributions, adapt to novel conditions, or die out. Consequently, accelerating climate change is already recognized as leading to considerable range expansion and contraction, evolutionary changes, and extinction for hosts, parasites, and diseases through the Arctic (e.g., Kutz et al., 2013; Meltofte et al., 2013). Ultimately, these perturbations have consequences for wildlife and humans at high latitudes (e.g., Dudley et al., 2015). Complex host-parasite systems are critical proxies for understanding change in northern regions due to species interactions that determine the distribution of parasites and disease over space and time (e.g., Hoberg et al., 2012, 2013). Life histories for helminth parasites (tapeworms, flukes, roundworms) often involve circulation among mammalian hosts (where adult parasites reside) and other vertebrate and invertebrate species (where larval or developing parasites reside). Other parasites (viruses, bacteria, protozoans) circulate through vectors such as blood feeding arthropods or through direct transmission. These complex life cycles are closely tied to environmental conditions, define linkages across communities, and scale from individuals to ecosystems.