Background/Question/Methods Large-scale anthropogenic changes to the natural environment including land use change, climate change, and the deterioration of ecosystem services are all accelerating.  These changes are combining synergistically to endanger the health and wellbeing of hundreds of millions of people through emerging threats in five main areas: increasing exposure to infectious disease, water scarcity, food scarcity, natural disasters, and population displacement.  Taken together, these emerging threats may represent the greatest public health challenge humanity has faced.  There is an urgent need to improve our understanding of the dynamics of each of these threats: the complex interplay of factors that generate them, the characteristics of populations that make them particularly vulnerable, and the identification of which populations are at greatest risk from each of these threats. 
In four chapters, we explore the health dimensions of land use change, disease ecology, climate change, and ecosystem service deterioration.  Each of these chapters illustrates the complexity of the relationship between human health and environmental change.  We describe the numerous mechanisms by which land use change can alter exposure to infectious disease.  We explore the often unforeseen consequences of changes in communities of organisms and their local environment to human infectious disease exposure.  We describe the likely health consequences of changes in the global climate and describe the importance of using an ecological lens to understanding and adapting to these changes.  Finally we discuss the relationship between deteriorating ecosystem services and health and explore the methodological challenges to rigorously proving adverse health outcomes from degraded ecosystem services.
Results/Conclusions Taken together, these chapters illustrate the complex vulnerability of human populations to accelerating, anthropogenic, environmental change.  They make it clear that these different types of environmental change may act synergistically to generate new threats to health and wellbeing.  Finally, they make it clear that an ecological perspective is critical to fully understanding these threats and beginning to help those at greatest risk.