Baltimore Sun, NYTimes: Chesapeake Trees + CO2 = Fatter, taller trees. News, indeed. Unanswered by reporters so far: so what?
For years – decades probably – agronomists and global warming theorists alike have said plant growth should and probably will get faster for at least awhile as rising CO2 provides vegetation with extras of an important nutrient. Controlled tests show that it does, at least until water shortages or stomata changes or other factors put on the brakes.
This week in PNAS a trio of Smithsonian researcher reports that a mix of tulip poplars, oaks, hickories, and beech trees in the wild, on 55 plots in one Chesapeake Bay woodland area in Maryland present a consistent picture – in recent decades their growth has spurted. It is twice to four times as fast as such trees were growing decades to two centuries ago. Main suspect: CO2. They also tried to account for directly linked factors such as temperature rise and longer growing seasons, plus others including fertilization via nitrogen or phosphorus from pollution.
As the paper says, such signs have been seen elsewhere and the changes generally agree with biogeochemical model predictions. Hence this seems to be an incremental part of an accumulation of information pointing in the same direction, all of which has suggests that a share of the recent fossil CO2 put into the air is transfering from the atmosphere into increased plant (and eventually, soil) biomass. The new study is pretty thorough to these eyes and, it says of itself, moves to the head of the pack in how it handles confounding variables. Remarkably, it reveals a growth jump in all age classes. The authors appear to have worked very hard to distinguish between likely CO2 and warming-modulated and growth and normal forest recovery after fire, farming, or other disturbance.
PNAS’s news staff did not highlight the study in their advance notice to reporters. But the Smithsonian put out a press release (in Grist below). The release reports that this is “evidence that forests in the Eastern United States are growing faster than they have in the past 225 years.” True. What the release does not do is address whether the results are a surprise or in line with other indications. How does this report change fundamental things? Do climate models already have a fudge factor for CO2 fertilization, and how might this calibrate it? The release does not say. Nor does the paper which, as it’s aimed at experts, need not. Do any reporters take possession of the story and try to find out for themselves how this fits into existing presumptions and science, and tell their readers?
For the most part, no luck. Some reporters treat the news as a revelation. That’s too bad. Somebody should take hold of this for a few days, call around a lot, and tell us the results.
Stories:
- Telegraph (UK): Trees ‘grow faster due to global warming’ ; This, it says, is a discovery.
- USA Today (short blog) Study: Trees are growing faster because of climate change ;
- NY Times – Leslie Kaufman: Study Finds a Tree Growth Spurt: The story provides plenty of caveats, but keeps its eye on this piece of news and has little context from existing literature. The two-to-four times rate of usual growth seems stunning. Are outside experts stunned?
- Baltimore Sun -Timothy B. Wheeler: Trees by the bay bulking up ; This one comes closest to addressing the so-what? question, but has it both ways. The second graf says without attribution that the results may mean “that forests might dampen or delay the impact of climate change, at least for awhile.” The clear implication is that such delay applies to contemporary forecasts from climate modelers. But well down, a Univ. of Maryland source tells him the results are “perfectly consistent” with what climate models project. Which is it? If both, the reporter should say there is argument over the study’s meaning.
Grist for the Mill: Smithsonian Inst. Press Release ;
- Charlie Petit
