Wish I had posted this on April 1st, but the good news just popped into my in-box last night.
Over at CO2Science.Org, Craig Idso reviews two extensive studies of the impacts of rising carbon dioxide (CO2) concentrations on trees in the Northern Hemisphere.
First, Idso reviews Soulé and Knapp (2015), a study of the growth and water-use efficiency of ponderosa pine and Douglas fir trees in the U.S. Forest Service’s Northern Rockies region since 1850.
The two researchers “collected tree-ring data from 14 different locations, from which information they were able to determine yearly changes (from AD 1850 to the present) in basal area increment (BAI) and intrinsic water-use efficiency (iWUE), the latter of which parameters they derived from yearly stable carbon isotope ratios (δ13C) of the trees’ annual layers of new-wood production.” Note: BAI means the area of a tree-trunk cross section at ground level.
What did Soulé and Knapp find? Both species experienced “exponentially increasing iWUE rates during AD 1850-present, suggesting either increased net photosynthesis or decreased stomatal conductance [i.e. decreased moisture loss via the stomatal pores of needles and leaves], or both.” In addition, “both species experienced above-average BAI in the latter half of the 20th century despite no favorable changes in climate.” The increase in BAI was observed “at all sites, suggesting a pan-regional effect.” Idso helpfully provides a chart illustrating the gains in water-use efficiency and growth.
Ah, but surely in Europe, where enlightened statesman demand draconian cuts in CO2 to save the biosphere, things are different. Nope.
Saurer et al. (2014), a study by 31 researchers from nine European countries who have established a network of 35 tree ring sites across the continent, also estimated changes in yearly water use efficiency (iWUE) from annual changes of carbon isotope ratios (δ13C) observed in tree rings.
Over the 100-year period from 1901 to 2000, Saurer et al. found “a strongly increasing trend” in water-use efficiency. Indeed, if we compare the first and last decades of the study period, mean water-use efficiency increased by more than 27%. Again, Idso kindly provides a chart illustrating the trend.
Of course, it is possible to have too much of a good thing. But so far, trees are soaking up “carbon pollution” as if it were–well, what it is–an essential nutrient whose direct biological benefits outweigh its potential indirect climate impacts.