Climate Change

Photo: Alexandra Fiord, Ellesmere Island, Nunavut © Greg Henry
International Tundra Experiment (ITEX) site, showing open-topped greenhouses, Alexandra Fiord, Ellesmere Island, Nunavut

Warmer temperatures lead to changes in the tundra biome

Evidence from around the circumpolar Arctic indicates that tundra is changing.18, 19 Climate records show that the particular conditions of cold temperatures and low precipitation needed to support polar tundra, barrens, and ice and snow biomes declined about 20% in the past 25 years.20 This trend is linked with increases in primary productivity and increased biomass in tundra plant communities. This “greening” signal is particularly strong in the Canadian Western Arctic where there is evidence of shrub cover increasing in the forest-tundra and adjacent tundra. Studies based on satellite images from 1986 to 2005 along the treeline zone west of Hudson Bay show trends to increased shrubbiness, especially west of the Mackenzie Delta.21 In the delta, the combination of warming temperatures and increasing permafrost degradation is creating new growing conditions suitable for colonization by tall deciduous shrubs such as alder.21

Several sites in Canada conduct research and monitoring on changes in tundra through the International Tundra Experiment (ITEX). Analysis of vegetation plots from ITEX sites around the circumpolar Arctic shows that, although changes vary from region to region, increases in vegetation canopy height and dominance of shrubs are common findings.22 The ITEX program also includes passive warming experiments using small, open-topped greenhouses (see photograph) which increase plant-level air temperature by 1 to 3°C. Analysis of 11 ITEX warming experiments from around the Arctic indicates that future trends in tundra are likely to include increases in canopy height, changes in species composition and abundance, and reduction in species diversity.23

Increases in evergreen shrubs and mosses, Ellesmere Island, Nunavut

Index of the mass of different vegetation categories, 1995 to 2007
Map and graph: increases in evergreen shrubs and mosses, Ellesmere Island, Nunavut. Click for graphic description (new window).
Source: adapted from Hudson and Henry, 200922

High Arctic tundra at the ITEX site on Ellesmere Island has become more productive, with biomass increasing by 50% over 13 years. This change was mainly due to an increase in growth of evergreen shrubs and moss. Because of the greater shrub growth, average canopy height increased, doubling from 17 to 34 cm between 2000 and 2007. Species diversity did not change.22

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