Generally, satellite observations of plant growth across the high latitudes of North America -- in Canada and Alaska -- indicate that tundra vegetation experienced an increase in both peak photosynthesis and growing season length, whereas forests experienced a decline in photosynthetic activity between 1981 and 2003. Climatic warming occurred across the entire region, but the change in the forest response indicates that long-term changes may not be predictable from initial, short-term observations. Fire disturbance has also increased with the warming but does not explain the decline in forest photosynthetic activity.
According to Scott Goetz, a senior scientist with the Center, "We believe this is some of the first evidence that high latitude forests may be in decline following an initial growth spurt associated with warming. The reasons for this decline are not certain, but related work points to increased drying as a likely cause. The observed warming and drying are consistent with climate model predictions for the region."
More specifically, Center researchers analyzed trends in a time series of photosynthetic activity across boreal North America over 22 years, from 1981 to 2003. Nearly 15 percent of the region displayed significant trends, of which just over half involved temperature-related increases in growing season, length an
Contact: Elizabeth Braun
Woods Hole Research Center