Is that a scary thing?
Guest post by Indur M. Goklany
In its October 14, 2010 issue, Nature magazine (p. 755) reports on a paper by JMG Hudson and G HR Henry, Increased plant biomass in a High Arctic heath community from 1981 to 2008, Ecology 90:2657–2663 (2009). (PDF ) It notes that, based on data collected from study plots over a 13-year period and survey data covering 27 years on the tundra of Ellesmere Island in Nunavut, Canada, an area where both temperatures and the length of the growing season has increased in recent decades:
“The biomass of mosses has increased by 74% and that of evergreen shrubs by 60%. The total biomass of the system has increased significantly, and vegetation has grown taller. But because there was plenty of open ground at the site into which plants could expand, these changes did not result in decreases in any group. The research indicates that climate change has already begun to increase plant productivity in the high Arctic.”
The abstract of the paper states:
“The Canadian High Arctic has been warming for several decades. Over this period, tundra plant communities have been influenced by regional climate change, as well as other disturbances… [W]e measured biomass and composition changes in a heath community over 13 years using a point-intercept method in permanent plots (1995–2007) and over 27 years using a biomass harvest comparison (1981–2008). Results from both methods indicate that the community became more productive over time, suggesting that this ecosystem is currently in transition. Bryophyte and evergreen shrub abundances increased, while deciduous shrub, forb, graminoid, and lichen cover did not change. Species diversity also remained unchanged. Because of the greater evergreen shrub cover, canopy height increased. From 1995 to 2007, mean annual temperature and growing season length increased at the site. Maximum thaw depth increased, while soil water content did not change. We attribute the increased productivity of this community to regional warming over the past 30–50 years. This study provides the first plot-based evidence for the recent pan-Arctic increase in tundra productivity detected by satellite-based remote-sensing and repeat-photography studies. These types of ground-level observations are critical tools for detecting and projecting long-term community-level responses to warming.”
In its penultimate paragraph, the paper admits that:
“The mechanisms for the observed increased productivity are unclear. However, it is likely that warming directly increased plant growth and reproduction and indirectly increased resource supply (Shaver et al. 2001). Increased temperatures also lengthened the growing season, increased soil temperature, deepened the active layer, and consequently may have influenced nutrient uptake in this plant community.”
Notably, the paper does not directly address the role, if any, that nitrogen and carbon fertilization may have played in the increased productivity. [One might argue this is implicit in the phrase in the above that refers to “indirectly increased resource supply.” If so, it’s a pretty sloppy piece of writing.] In any case, based on its findings, it expresses some skepticism about claims that many heath species may be endangered:
“Although many heath species are predicted to become endangered by their inferior competitive abilities (Callaghan et al. 2005), our results indicate that heath plant communities may persist in a warmer future in the High Arctic.”
The paper also points out that its findings are consistent with satellite-based analyses that show increasing productivity in the Arctic area. See the earlier WUWT post, Another Al Gore Reality Check: “Rising tree mortality”?, that shows that it is not only the Arctic region that has greened up, but also the Sahel, Australia, the Amazonia, and the world as a whole.
So, going back to the heading of this piece, is increased biological productivity something to be scared about?
The answer is “yes” only if:
(a) Any change is bad, which apparently many in the environmental community believe reflexively, AND
(b) Nature (including humanity) cannot adapt to any warming that might result.
But an increase in productivity isn’t just any change. It actually makes more resources available to life forms that rely on them for sustenance. That is, it could lead to more abundant, if not more diverse, species. Moreover, we know that nature has encountered as much if not greater warming in the Arctic regions before, and is none the worse for it. See, for example, CO2 Science’s Medieval Warming Project Interactive Map and Time Domain Plot.