One Health in a world with climate change.

The One Health movement, as defined in this paper, has progressed from a focus on emerging infectious diseases to a broader set of challenges that include food security and food safety. These interact with climate change, a so-called 'wicked problem' that has links to all human activity. Climate change acts as a threat multiplier that interacts both directly and indirectly with variables, such as disease, food production, food security, food safety and poverty. A number of these interactions are briefly described in this paper before issues of complexity and interconnectedness between these variables are discussed. A common thread underpinning this current global challenge to civilisation is that the system is now dominated by the activities of humans--and many scientists label the current epoch the 'Anthropocene'. Specifically, humans have for the first time collectively overloaded the Earth's capacity to supply, absorb, replenish and stabilise. Many scientists now observe that the ecological and environmental foundations of civilisation appear to be at risk. This paper suggests that, for the One Health movement to address such challenges, the range and number of disciplines that need to be involved must be expanded. In particular, in addition to the insights provided by technical specialists, we need to engage disciplines with the capacity to advance political, economic and social reforms. This will not be easy, but it is argued that this is what is required from the One Health movement in a world with climate change.