Competing interests: We have read and understood BMJ policy on declaration of interests and declare the following interests: AH received funds through LSHTM from the Rockefeller Foundation to support activities of the Commission on Planetary Health. He is also coinvestigator on three project grants funded by the Wellcome Trust. He chairs the development team of the Future Earth Health knowledge action network. FH receives funds from United Nations University and the University of Tokyo for organisational and project support in the development of the health network. She also receives support from a Wellcome Trust grant for her research at LSHTM. CM is science officer for the oneHEALTH project, which is supported by contributions from DIVERSITAS, Future Earth, and EcoHealth Alliance.