"The Arctic holds some of the most extreme habitats on Earth, with species and peoples that have adapted through biological and cultural evolution to its unique conditions. A homeland to some, and a harsh if not hostile environment to others, the Arctic is home to iconic animals such as polar bears Ursus maritimus, narwhals Monodon monoceros, caribou/reindeer Rangifer tarandus, muskoxen Ovibos moschatus, Arctic fox Alopex lagopus and snowy owls Bubo scandiaca, as well as numerous microbes and invertebrates capable of living in extreme cold, and large intact landscapes and seascapes with little or no obvious sign of direct degradation from human activity. In addition to flora and fauna, the Arctic is known for the knowledge and ingenuity of Arctic peoples, who thanks to great adaptability have thrived amid ice, snow and winter darkness. The purpose of this Arctic Biodiversity Assessment (ABA) is to synthesize and assess the status and trends of biodiversity in the Arctic and provide a first and much-needed description of the state of biodiversity in the Arctic (see Section 0.2 in the Introduction for this assessment’s definition of the Arctic). It creates a baseline for global and regional assessments of Arctic biodiversity, and is a basis for informing and guiding future Arctic Council work. It provides up-to-date knowledge, identifies data and knowledge gaps, describes key mechanisms driving change and presents science- based suggestions for action to address major pressures. The ABA identifies current status together with historical trends in abundance and distribution where available, and includes projections of future change informed by scientific literature. It draws on a vast number of scientific publications, supplemented by ‘eye witness’ observations from indigenous peoples in the context of Traditional Ecological Knowledge (TEK). The ABA has been through comprehensive peer review to ensure the highest standard of analysis and unbiased interpretation. The results are a benchmark against which to help measure and understand the significance of future change, without which the scope and gravity of future changes will be less clearly identifiable, undermining our ability to reduce harm. Change in the Arctic comes in many forms and from a variety of sources. Several of these stressors have been the subject of intense research and assessments documenting the effects and impacts of human activity regionally and globally, and seeking ways to conserve the biological and cultural wealth of the Arctic in the face of considerable pressures to develop its resources. These assessments have focused primarily on effects and impacts from a range of present and future stressors, such as global warming (ACIA 2005, AMAP 2009a, AMAP 2011a), oil and gas activities (AMAP 2009b), social change (AHDR 2004), marine shipping (AMSA 2009), and environmental contaminants (AMAP 1998, 2004, 2010, 2011b). The ABA, in contrast, looks not at the stressors but at the biodiversity being stressed. The ABA consists of four components: (1) Arctic Biodiversity Trends 2010 – Selected Indicators of Change, which provided a preliminary snapshot of status and trends of Arctic biodiversity (Box 1.1), (2) the present full scientific assessment of Arctic biodiversity, (3) Cycles of life: indigenous observations of change and (4) Arctic Biodiversity Assessment: Summary for Policy Makers." /./