nitrogen deposition problem. Major regions of the world are exceeding sustainability thresholds for adverse effects on ecosystem function and biodiversity. This highlights the importance of ongoing work, including under the Convention on Biological Diversity, in developing indicators and monitoring nitrogen deposition effects to enable appropriate measures. This book presents a milestone towards this global goal as the international community works toward meeting the Aichi Biodiversity Targets, especially Target 8: "By 2020, pollution, including from excess nutrients, has been brought to levels that are not detrimental to ecosystem function and biodiversity". Braulio Ferreira de Souza Dias, Executive Secretary, Convention on Biological Diversity ¿This key volume highlights the global challenge to reduce atmospheric nitrogen pollution resulting from energy production, transport and agricultural activities. It takes forward the agenda recently launched in the UNEP commissioned report ¿Our Nutrient World¿. Dr. Anjan Datta, UNEP.