Achim Steiner has lived one of the most remarkable international lives of his generation. The son of a German farmer who emigrated to Brazil, he was born in Rio Grande do Sul in 1961, a dual citizenship that would come to embody a career defined by crossing borders. He began not in the grand halls of the United Nations but in the field, working on rural development in Germany before moving to the International Union for Conservation of Nature across Southern Africa and Washington. From there his career traced the fault lines of the planet's ecological crisis: advising on the contested waters of the Mekong, leading the World Commission on Dams, then returning to the IUCN as Director-General just as climate change became the defining challenge of the age. In 2006, nominated by Kofi Annan, the General Assembly unanimously elected him Executive Director of UNEP, a mandate renewed and extended as he steered global environmental policy through Cancún, Doha, and Paris. He crowned that effort at the helm of the UN Development Programme, before returning to Oxford as Senior Fellow of the Oxford Martin School.