Ian Murray wrote:
> As if the only reason we should plant trees is to sequester carbon!
> [from the NYT]
> May 24, 2001
> Studies Challenge Role of Trees in Curbing Greenhouse Gases
> By ANDREW C. REVKIN
> Two new studies are challenging the idea that planting forests could
> be a cheap way to absorb emissions of carbon dioxide, the main heat-
> trapping gas released by human activities.
> In one, tracts of pine trees exposed to elevated levels of the gas
> initially absorbed large amounts and had a short growth spurt, but
> then reverted to typical growth rates.
> A separate study of the soil around the exposed trees found that,
> although it accumulated carbon, much of the carbon was released back
> into the air as carbon dioxide when organic material in the soil
> The studies, described in today's issue of the journal Nature, were
> limited to loblolly pine forests in North Carolina, but the authors
> said their findings suggested a limit to the value of forest planting
> to counter carbon dioxide emissions from smokestacks and tailpipes
> that many scientists say are warming the climate.
> "Such findings call into question the role of soils as long-term
> carbon sinks," wrote the authors of the soil study, Dr. John Lichter,
> a biologist at Bowdoin College, and Dr. William H. Schlesinger, a
> professor of biogeochemistry at Duke University, which owns the forest
> where the research was done.
> Forest planting has figured in negotiations on a global agreement to
> reduce greenhouse gases, and the United States, Canada, Japan and some
> other large industrial countries have backed the idea.
> But the new research suggests the approach is not as effective as
> advocates had hoped. The study of tree growth, led by Dr. Ram Oren, an
> ecologist at Duke, concluded that previous estimates of forests'
> carbon-absorbing abilities were "unduly optimistic."
> Several scientists not involved in the studies said the research
> provided some of the first hard evidence showing the response of trees
> to carbon dioxide and, among other things, should help improve
> computer models used to predict how the rise in heat-trapping gases
> might affect the climate and ecosystems.
> Others added that the work challenges a longstanding assertion of some
> coal and power companies that the main consequence of rising levels of
> carbon dioxide in the air will not be a damaging warming of the
> climate, but rather a flourishing of forests and other plant life.
> Some scientists stressed that the Duke findings - despite the years of
> monitoring - still are preliminary because forests can take a long
> time to adjust to changes in the environment, and the conditions noted
> so far may only be a prelude to other shifts.
> And some scientists involved in related experiments looking at the
> absorption of the gas by croplands and grassland said they thought
> that some of the researchers' conclusions were gloomier than their
> Dr. Bruce A. Kimball, a soil scientist who has studied the response of
> wheat and cotton to elevated carbon dioxide at a Department of
> Agriculture laboratory in Phoenix, noted that the Duke soil findings,
> over all, still showed an increase in retained carbon. He said tree
> planting could have "some significant impact on offsetting some of our
> CO2 emissions."
> He conceded, however, that the abrupt drop in the growth rate of the
> trees was "discouraging."
> The study is described on a Department of Energy Web site at
Michael Perelman Economics Department California State University Chico, CA 95929
Tel. 530-898-5321 E-Mail michael at ecst.csuchico.edu