Apr 10, 2012
Insight: plant biomass in Arctic tundra has increased
The aboveground live biomass of Arctic tundra vegetation has increased by 19.8%, on average, throughout the circumpolar North since 1982, according to a study by researchers from the University of Virginia and the University of Alaska Fairbanks, US (Environmental Research Letters (ERL)).
The analysis was based on the strong relationship between plant biomass measured in the field and a "vegetation greenness" index derived from satellite observations. The field biomass measurements were taken from 13 sites over the course of nine summer Arctic expeditions, spanning gradients of over 1500 km in both the North American and Eurasian Arctic. Satellite data came from the Advanced Very High Resolution Radiometer (AVHRR) onboard National Oceanic and Atmospheric Administration (NOAA) satellites. With these relationships in place, the satellite data were then used to analyse the changes in tundra vegetation biomass throughout the Arctic from 1982 to 2010.
The southernmost areas of tundra, which are dominated by tall shrubs and dwarf erect shrubs, showed the largest biomass increases, ranging from 20 to 26%. There was, however, a high degree of variation, with Alaskan tundra showing a biomass increase of 7.8%, Canadian tundra increasing by 36.5%, and Russian tundra increasing by 15.7%. Even within Alaska there were large differences – tundra biomass in Northern Alaska increased by 32.2%, whereas Beringian Alaska showed biomass declines of 3.5%. Overall, increasing biomass was rather ubiquitous throughout the Arctic tundra, with only two sub-regions showing biomass decline.
The estimated increase in carbon in the aboveground live vegetation totals 0.40 petagrams (Pg) over the past three decades. One Pg is 1015 grams. This is substantial, but still quite small compared to man-made carbon dioxide emissions, which are now around 10 Pg per year. This additional amount of carbon in the live vegetation could, however, represent an important fraction of the annual terrestrial ecosystems' carbon sink in the Arctic, which has been estimated to lie in the 0.3–0.6 Pg C range.
The 19.8% average increase in aboveground biomass has major implications for Arctic tundra ecosystems, including their hydrology, permafrost and wildlife, and for how humans exploit Arctic landscapes. The taller and denser vegetation uses up more carbon from the atmosphere, changes the amount and composition of forage for grazing animals, and also alters the partitioning and distribution of energy and heat at the land surface.
About the author
Howard E Epstein is a professor in environmental sciences at the University of Virginia, US. His research focuses on vegetation dynamics and biogeochemical cycling in a variety of ecosystems, including Arctic tundra, grasslands and deserts, and temperate forests. He has been working in the Arctic since 1996 and has participated in nine summer expeditions to 10 different Arctic locations since 2002.