The Subarctic City: Metropolitisation, Abandoned Towns and Increases of Risk Vulnerabilities

International audienceArctic and Subarctic cities and settlements depend of the economic, political and societal changes. In the Siberian arctic and subarctic territories as in Yakutia, the dynamics of urbanisation and un-urbanisation are strong. Abandoned mine’s tows, stable cities (Mirnyj), partially abandoned like Tiksi, fast urban growth and metropolisation in Yakutsk. Adaptation to the climate change, globalization and societal transformations constitute a heavy challenge, notably to the sustainable development issues. The Yakutsk region of Eastern Siberia has experienced unprecedented urbanization growth over the last 25 years with more than 330000 inhabitants in 2016 out of a total population of about 980000 people in the Republic of Sakha. It is located along the Lena River on the permafrost bioclimatic belt, which is subject to annual flooding of the ice breakup. The territory in Yakutsk metropolitan area is also dramatically impacted by water and aerosol pollution ("smoke" effects). The effects of global warming are de facto increasing the exposure of urban and peri-urban populations to the multi-dimensional risks associated with permafrost (weakening and collapse of buildings). Annual flooding of ice breakups in peri-urban areas can cause their destruction as in 1950’s and 1960’s in a context of urban growth and densification (verticalisation) often on sandy soils and subject to partial thaw. In addition, in urban areas, exposure to epidemiological risks linked to soil thaw can be a hidden issue or simply ignored. Thus, in addition to the effects of the Lena flood-break-up, localities are likely to increase the environmental risk and themselves become sources of local and global pollution. By exposing their own populations to risks, they reinforce the effects of global warming through their economic activities (shipping, mining industries, etc.). In light of these questions, there is the question of the coping capacities / resilience of circumpolar populations and cities with multiple risks and for some in a context of emerging metropolisation. Several challenges affect Yakutia territory in the triple context of climate changes, increasing exposure of natural risks, and massive urban transformations: metropolisation dynamics in Yakutsk, decreasing of populations in the Arctic settlements, multiple exposures of populations to the flooding, pollution, permafrost melting, etc. If the local populations would implement territorial strategies and develop specific behavioural patterns to the annual flooding for example, the massive transformations of the region of Yakutsk would generate new challenges and impose interdisciplinary approach combining local knowledge, participatory approach, GIS, and remote sensing monitoring. The lack of systematic data as well as monitoring of the fast territorial transformations and urban sprawl has broken the dynamics of resilience and adaptation made before by the local populations in the flooding areas, permafrost risk zones, and polluted spaces. This aspect constitutes a challenge for the sustainability of Yakutsk. The absence of clear scenarios, assessment of potential impacts and consequences of the climate change, territorial dynamics, and societal transformations also threatens sustainability of the city. Approach under development combines three methods: remote sensing monitoring of the urban and territorial transformations, spatial modelling of the gradient of risk exposures, monitoring and modelling of annual or constant geophysical and environmental hazard, and integrates human adaptation strategies and resilience. The institutional response in terms of planning was during the Soviet period to build a dyke protecting the historic city of ice breakup floods and the development of building construction methods on permafrost whose standards were in 2016 eased. The Soviet culture of this former closed territory associated with strong local land and real estate interests and strong family interrelations, irrigates the operating modes in terms of institutional, collective and individual responses. This culture of confidentiality makes it difficult to access even the most basic databases and collected cartographies; moreover, these data when they are accessible are most often obsolete. The only data available come from the use of civil satellite images in open sources and from American programs LANDSAT, French SPOT and more recently European Sentinel Earth observation constellations