Background
The authors write that "climate warming is pronounced at high northern latitudes (ACIA, 2005; Serreze, 2010)," and that "time series analysis of satellite remote sensing between 1982 and 2008 suggests that there has been a greening of arctic landscapes," citing Bhatt et al. (2010). More particularly, they note that "remotely detected changes in the normalized difference vegetation index (NDVI) of the arctic coastal plain near Barrow, Alaska, appear to be among the most dramatic recorded for much of the Arctic," once again citing Bhatt et al. (2010). However, they say "there is a general scarcity of ground-based studies that examine vegetation change in the Arctic over decade time scales," and it was this research niche that their study was designed to fill.

What was done
Focusing on an area near Barrow at the northernmost point of the Alaskan Coastal Plain (71°18'N, 156°40'W), Villarreal et al. resampled (for species cover and presence, in 1999, 2008 and 2010) 330 marked plots at 33 sites that had been established there in 1972 as part of that year's International Biological Program.

What was learned
The six scientists report that over the 38-year study period, ecosystem diversity "increased for most plant communities, and wetter communities changed more than dry and moist plant communities." These findings are said by them to support other observational studies, such as that of Wilson and Nilsson (2009). And of the 19 species that comprised more than 80% of the overall relative cover, they say that five had higher relative cover in 2010 than 1972. In addition, they indicate that their results for changes in shrub cover "are somewhat consistent with other long-term observations and experimental studies that report increased shrub abundance (Myers-Smith et al., 2012; Tape et al., 2006; Walker et al., 2006; Sturm et al., 2001)," as well as warming-induced "treeline advancement (Lloyd, 2005; Danby and Hik, 2007)."

What it means
Come hell or high-water, the greening of planet earth continues.

References
ACIA. 2005. Arctic Climate Impact Assessment - Scientific Report, 1st edition. Cambridge University Press, Cambridge, United Kingdom.

Bhatt, U.S., Walker, D.A., Raynolds, M.K., Comiso, J.C., Epstein, H.E., Jia, G.J., Gens, R., Pinzon, J.E., Tucker, C.J., Tweedie, C.E. and Webber, P.J. 2010. Circumpolar Arctic tundra vegetation change is linked to sea ice decline. Earth Interactions 14: 1-20.

Danby, R.K. and Hik, D.S. 2007. Variability, contingency and rapid change in recent subarctic alpine tree line dynamics. Journal of Ecology 95: 352-363.

Lloyd, A.H. 2005. Ecological histories from Alaskan tree lines provide insight into future change. Ecology 86: 1687-1695.

Myers-Smith, I.H., Hik, D.S., Kennedy, C., Cooley, D., Johnstone, J.F., Kenney, A.J. and Krebs, C.J. 2012. Expansion of canopy-forming willows over the 20th century on Herschel Island, Yukon Territory, Canada. AMBIO 40: 610-623.

Serreze, M.C. 2010. Understanding recent climate change. Conservation Biology 24: 10-17.

Sturm, M., Racine, C.H. and Tape, K.D. 2001. Increasing shrub abundance in the Arctic. Nature 411: 546-547.

Tape, K., Sturm, M. and Racine, C. 2006. The evidence for shrub expansion in northern Alaska and the Pan-Arctic. Global Change Biology 12: 686-702.

Walker, M.D., Wahren, C.H., Hollister, R.D., Henry, G.H.R., Ahlquist, L.E., Alatalo, J.M., Bret-Harte, M.S., Calef, M.P., Callaghan, T.V., Carroll, A.B., Epstein, H.E., Jónsdóttir, I.S., Klein, J.A. , Magnússon, B.ó., Molau, U., Oberbauer, S.F., Rewa, S.P., Robinson, C.H., Shaver, G.R., Suding, K.N., Thompson, C.C., Tolvanen, A., Totland, Ø., Turner, P.L., Tweedie, C.E., Webber, P.J. and Wookey, P.A. 2006. Plant community responses to experimental warming across the tundra biome. Proceedings of the National Academy of Sciences USA 103: 1342-1346.

Wilson, S.D. and Nilsson, C. 2009. Arctic alpine vegetation change over 20 years. Global Change Biology 15: 1676-1684.