Anthropogenic climate change is dramatically affecting regions of the world that have historically had cold, snowy winters. Yet the vast majority of studies on climate-disease links investigate how hosts or parasites are impacted by warm conditions getting hotter in either tropical regions or the growing season of temperate regions. Much less is known about how cold climates and winter seasons, or changes in winter conditions, affect host-parasite interactions. There is conventional wisdom among farmers and plant pathologists that very cold and snowless conditions will kill off plant pathogens between cropping seasons, but even in well studied agricultural systems this is a greatly understudied topic. I propose that effects of cold/winter climate on the ecology and evolution of infectious diseases can and should be studied synergistically for parasites of plants and animals. To illustrate this, I review the literature on mechanisms by which climatic variables including cold, ice, and snow affect a range of parasite types across diverse host taxa. I present a synthesis of this literature survey, with particular emphasis on (1) identifying key mechanisms that are likely important for diseases of plants and animals alike, and (2) highlighting future directions for productive synergistic research on this topic.
Results/Conclusions
For parasites that spend at least part of their life cycle in the environment, winter can pose extreme challenges. Such challenges include physiological stresses of freezing or ice damage, and decreased availability of hosts. In some systems, however, winter conditions increase the success of parasites infecting either animal or plant hosts. Prolonged cold can also allow for long-term viability of many parasitic organisms. At the same time, the onset of winter triggers a switch from asexual to sexual reproduction of certain parasites (and in some cases, hosts), which can have consequences for parasite genetic diversity and (co)-evolutionary dynamics. Understanding the mechanisms by which cold, ice, and snow affect a diverse array of parasites (including viruses, bacteria, fungi, and parasitic eukaryotes) is essential for predicting how changes in polar and temperate climates will affect infection risk for plants and animals, including humans. Importantly, many of these mechanisms are more specific to features of parasite biology than host taxonomy. Identifying mechanisms that span the host taxonomic divide, and gaps in current knowledge of such mechanisms, will be critical for planning synergistic research programs that accelerate advances in climate change research for diseases of plants and animals.