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The Canadian Arctic is Greening

Jia, G.J., Epstein, H.E. and Walker, D.A. 2009. Vegetation greening in the Canadian Arctic related to decadal warming. Journal of Environmental Monitoring 11: 2231-2238.
It is often claimed that anthropogenic global warming will have widespread adverse effects on ecosystems; and one of the regions claimed to be most fragile in this regard is the Arctic. This study thus utilizes 25 years of satellite data covering the period of most rapid recent warming (1982 to 1996) to evaluate this claim via Normalized Difference Vegetation Index (NDVI) data obtained from the GIMMS dataset -- which is comprised of 64-km2 cells -- minus those cells with too much open water or bare ground within them that are known to inject significant bias into NDVI data analyses.

The study showed that tundra ecosystems exhibited an average increase in greenness of 5.6%/decade over 96% of the pixels evaluated, which greening trend was proportional to the rate of summer warming as measured by growing degree days. With respect to the components of the greenness trend, Jia et al. report it was next-to- lowest in the high arctic, which is dominated by bare ground and water; and they state that the boreal forest showed no trend at all. However, a later paper by a related team of authors (Alcaraz-Segura et al., 2010) found that GIMMS data are not reliable for the boreal forest zone, where the greening trend, if any, thus remains unknown.

Responding most strongly of all ecosystems, the three researchers say that the decadal increases of vegetation greenness over the tundra biome in summer "reflect increasing vegetation productivity during the growing season." In addition, they discovered a tendency for the three most northern (of five) arctic zones to show a slight advance in the date of peak NDVI, although the resolution of the data was such that it did not enable much precision in estimating timing changes.

In conclusion, therefore, when combined with the results of Alcaraz-Segura et al. (2010), the results of these studies depict a significant increase in vegetative growth for the entire boreal-to-arctic zone of Canada, which is certainly good news for this vast biologically awakening region.

Additional Reference
Alcaraz-Segura, D., Chuvieco, E., Epstein, H.E., Kasischke, E.S., and Trishchenko, A. 2010. Debating the greening vs. browning of the North American boreal forest: differences between the satellite datasets. Global Change Biology 16: 760-770.

Archived 1 June 2010