Abstract
Abstract. Exploration and exploitation of oil and gas reserves of northern West Siberia has promoted rapid industrialization and urban development in the region. This development leaves significant footprints on the sensitive northern environment, which is already stressed by the global warming. This study reports the region-wide changes in the vegetation cover as well as the corresponding changes in and around 28 selected urbanized areas. The study utilizes the normalized difference vegetation index (NDVI) from high-resolution (250 m) MODIS data acquired for summer months (June through August) over 15 years (2000–2014). The results reveal the increase of NDVI (or “greening”) over the northern (tundra and tundra-forest) part of the region. Simultaneously, the southern, forested part shows the widespread decrease of NDVI (or “browning”). These region-wide patterns are, however, highly fragmented. The statistically significant NDVI trends occupy only a small fraction of the region. Urbanization destroys the vegetation cover within the developed areas and at about 5–10 km distance around them. The studied urbanized areas have the NDVI values by 15 to 45 % lower than the corresponding areas at 20–40 km distance. The largest NDVI reduction is typical for the newly developed areas, whereas the older areas show recovery of the vegetation cover. The study reveals a robust indication of the accelerated greening near the older urban areas. Many Siberian cities become greener even against the wider browning trends at their background. Literature discussion suggests that the observed urban greening could be associated not only with special tending of the within-city green areas but also with the urban heat islands and succession of more productive shrub and tree species growing on warmer sandy soils.
Highlights
Significant shifts in the vegetation land cover and biological productivity manifest rapid climate change in the northern high latitudes (Hinzman et al, 2005; Groisman and Gutman, 2013)
Two novel aspects should be mentioned in this context: (1) whereas the previous studies analyzed coarse-resolution data, which is likely to exaggerate the extent and magnitude of the NDVImax trends (Zhao et al, 2009; Elsakov and Teljatnikov, 2013), we use the fine-resolution (250 m) data; and (2) fine-resolution data give an opportunity to trace the changes to specific biomes within the same bioclimatic zone and to reveal effects of urban disturbances
We observe that NDVImax is significantly higher on river terraces with better-drained, sandy soils, which are warmer in summertime and have deeper seasonal active layer
Summary
Significant shifts in the vegetation land cover and biological productivity manifest rapid climate change in the northern high latitudes (Hinzman et al, 2005; Groisman and Gutman, 2013). Its attribution to tall shrub and graminoids in tundra ecosystems (Frost and Epstein, 2014) and enhanced tree growth in forest-tundra ecosystems (Urban et al, 2014) suggested that we observe transitions to alternative, potentially more productive ecosystems rather than anomalously enhanced biological productivity in response to global warming (Kumpula et al, 2012; Macias-Fauria et al, 2012) These environmental shifts have been unfolding for at least the last 3 decades (Keeling et al, 1996; Myneni et al, 1997) albeit at a slower pace since 2003 (Bhatt et al, 2013).
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