Volume 4, Number 51: 19 December 2001
Several years ago, when I published a short note in Nature that bore this title (Idso, 1986), few people took seriously the proposition I put forth at that time, i.e., the idea that the aerial fertilization effect of the carbon dioxide liberated by the burning of the coal, gas and oil that fueled the development of industrial civilization was destined to dramatically enhance the productivity of the planet's vegetation. How dramatically, you ask? In a little book I had published some years earlier (Idso, 1982), I predicted that "CO2 effects on both the managed and unmanaged biosphere will be overwhelmingly positive," if not "mind-boggling." And in a monograph based on a lecture I gave some years later (Idso, 1995), I said "we appear to be experiencing the initial stages of what could truly be called a rebirth of the biosphere, the beginnings of a biological rejuvenation that is without precedent in all of human history."
Given this background, you can probably appreciate why no one has ever accused me of being a pessimist. I have, however, been accused of being wrong ... many times, in many settings, and over many years. But when I read the reports of new research being done these days, I get a nice warm feeling. And its not from global warming.
The titles of the reports to which I refer sound a lot like they were written by my younger clone. 'Greenhouse' Growing Greener on Patches of Earth, Study Finds and Adult Amazon Trees Gain Mass, Puzzle Scientists are two of the most recent such stories to hit the streets (of the internet, I guess I should say), courtesy of the National Geographic News.
The last of these research reports appeared just a few days ago, on 13 December 2001. It begins by stating "research has shown" - not models, mind you - "that mature forest trees in the Amazon have gained in size over the last 20 years," which finding is described as "unexpected," because "mature forests were thought to be 'carbon neutral,' giving off as much carbon as they absorb each day." Not to wander too far off the politically-correct path, of course, the report says "scientists aren't sure what's causing it," and they don't know "what effect it might have on global warming."
It's hard to totally submerge the truth, however, and it begins to surface when the leader of the research team responsible for the work is reported to be leaning towards the explanation that "the Amazon forests have become more massive as a result of increased amounts of carbon dioxide in the atmosphere" and it is further admitted that "the increased mass of Amazonian forests suggests they are acting as a huge 'carbon sink,' absorbing more carbon from the atmosphere than they release." But the stab at candor is short-lived, as the report describes an alternative explanation for the unexpected growth of the mature trees, which is "that the forests are receiving more nutrients than previously as the result of human activities".
Had I been writing the report, I would probably have italicized the last six words of this sentence - as the result of human activities - for this phrase acknowledges that even the alternative explanation for the welcome increase in tree growth has its roots in the actions of man. By way of explanation, "forest fires," the following sentence continues, "are releasing increased amounts of nitrogen into the atmosphere [where] the nitrogen is absorbed by clouds and returned to Earth as rain, which fertilizes the forests," revealing the additional fact that forest fires can also have a positive side to them.
Yes, good news is often hard to pry out of today's reporters; and a couple of paragraphs later we are told that "controlled experiments conducted in forest plots at Duke University in North Carolina have shown that the increased carbon absorption benefit of forests resulting from increased carbon dioxide lasts only a few years." Actually, it is the Duke University experiments that have lasted "only a few years." Of what the long-term future holds, no one can be totally certain. I can report, however - in fact, I have (Idso and Kimball, 2001) - that after 13+ years of enriching sour orange trees with an extra 75% CO2, both wood and fruit production in the CO2-enriched trees is continuing to be enhanced -- and by approximately 80%.
After finally admitting that "nitrogen supply is unlikely to be a problem in tropical forests," the author of the report - perhaps to compensate - quotes a project scientist as wondering "what will happen if dry seasons become longer and more severe." Here another quote, this time from a climate modeler, provides the politically-correct answer: "forests could dry out and become a source rather than a sink of carbon." Well, I suppose they could experience drier weather; but most climate models predict a largely wetter world in the future, although one cannot deny the possibility of modest drying in some specific areas. So, what if there was a slight reduction in water availability?
In a study of 23 carbon isotope tree-ring chronologies obtained from trees growing in natural forests located (primarily) throughout western North America, Feng (1999) derived histories of plant intrinsic water use efficiency that rose by 10 to 25% from 1750 to 1970, while the CO2 concentration of the atmosphere simultaneously rose by approximately 16%. He concluded from these real-world data that "in arid environments where moisture limits the tree growth, biomass may have increased with increasing transpiration efficiency," suggesting to him that the enhanced growth of trees in arid environments may thus "have operated as a carbon sink for the anthropogenic CO2." Hence, it seems likely that any drying of the Amazon would pose little problem to its trees in a world of rising atmospheric CO2 concentration.
Agonizingly, the report oscillates back and forth between the demonstrable good and the speculative bad. In describing what he calls the "unexpected bonus" of enhanced mature tree growth, for example, the leader of the study is quoted as saying "I don't think anyone expects it will go on forever." Indeed, not even I go that far ... but it's tempting. The study of Feng traces the aerial fertilization/anti-transpirant effect of atmospheric CO2 enrichment back some 200 years, to where the air's CO2 content first began to respond to the engines of the Industrial Revolution, as does the study of Graybill and Idso (1993). In the other direction, the reports of Condit et al. (1995) and Chambers et al. (1998) indicate that several of the trees of Central and South America can live for nearly one and a half millennia; while the study of Carey et al. (2001) indicates that because of long-term recruitment and the periodic appearance of additional late-successional species, the carbon sequestering prowess of real-world forests extends - and intensifies - far beyond the lifetimes of the individual trees comprising them. Yes, forests and their appetites for carbon may not be the diamonds some have said "are forever," but they appear to be persistent enough to far outlast what we could call the Age of Fossil Fuels.
The other report I mentioned near the beginning of this editorial tells a similarly heart-warming story, to me at least. Based on satellite data collected over the past two decades - which is, I believe, the period of "unprecedented" warming so disturbing to climate alarmists - earth's "greenhouse," as the writer refers to it, has been "growing more lush." Specifically mentioned are forests and woodlands extending from central Europe through Siberia to far-east Russia, as well as forests in eastern North America. These forests too, the report notes, "may already be siphoning off larger-than-expected amounts of carbon." But like the other report, its writer quotes one of the project scientists as saying "as to how much and for how long, that needs more research."
So, have my prophecies been vindicated? Not yet to their fullest, obviously; but the odds in favor of their being ultimately proved correct are beginning to look considerably better with each passing day ... and with each new report of research that probes the real world of nature, as opposed to the virtual world of model-generated climate fantasy.
Dr. Sherwood B. Idso
Carey, E.V., Sala, A., Keane, R. and Callaway, R.M. 2001. Are old forests underestimated as global carbon sinks? Global Change Biology 7: 339-344.
Chambers, J.Q., Higuchi, N. and Schimel, J.P. 1998. Ancient trees in Amazonia. Nature 391: 135-136.
Condit, R., Hubbell, S.P. and Foster, R.B. 1995. Mortality-rates of 205 neotropical tree and shrub species and the impact of a severe drought. Ecological Monographs 65: 419-439.
Feng, X. 1999. Trends in intrinsic water-use efficiency of natural trees for the past 100-200 years: A response to atmospheric CO2 concentration. Geochimica et Cosmochimica Acta 63: 1891-1903.
Graybill, D.A. and Idso, S.B. 1993. Detecting the aerial fertilization effect of atmospheric CO2 enrichment in tree-ring chronologies. Global Biogeochemical Cycles 7: 81-95.
Idso, S.B. 1982. Carbon Dioxide: Friend or Foe? IBR Press, Tempe, AZ.
Idso, S.B. 1986. Industrial age leading to the greening of the Earth? Nature 320: 22.
Idso, S.B. 1995. CO2 and the Biosphere: The Incredible Legacy of the Industrial Revolution. Department of Soil, Water & Climate, University of Minnesota, St. Paul, MN.
Idso, S.B. and Kimball, B.A. 2001. CO2 enrichment of sour orange trees: 13 years and counting. Environmental and Experimental Botany 46: 147-153.