Ben Collen is head of the Indicators & Assessments Unit at the Zoological Society of London.  His research is focussed on developing indicators to monitor change in biodiversity and help guide policy responses to conservation problems.  He conducts local scale monitoring on tropical forest fauna in Liberia, and penguins in the Antarctic. Nathalie Pettorelli is a population ecologist, whose research is centred on predicting the impacts of global environmental change on biodiversity. Her work was among the first to explore the usefulness of satellite data (in particular, the Normalised Difference Vegetation Index) in the context of population ecology and dynamics. Jonathan Baillie is Director of Conservation at the Zoological Society of London. He is responsible for conservation projects focusing on threatened species and habitats in over 50 countries around the world. His research focus lies in defining the status and trends of the world's species and ecosystems. Sarah Durant is head of the Tanzania Carnivore Centre in Arusha, and the Range Wide Conservation Initiative for Cheetah and Wild Dog. She has been working for over 20 years in carnivore conservation in Africa, focussing on developing effective and sustainable approaches to conserve threatened species.