Beginning with a review of how Earth and our understanding of it have changed over the last 25 years, this chapter considers many of the key indicators of the advancing environmental and climate crisis and the health implications of the changes that are occurring. Also of keen concern are the underlying social structural causes of Earth’s contemporary ecocrises, including species extinction and loss of biodiversity. The chapter highlights the ecosyndemics research of anthropologist Paula Skye Tallman. The chapter locates the study of ecosyndemics in critical health anthropology theory.