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program of this magnitude. Any comparison with current forest growth rates must acknowledge that most of the increased growth envisioned in the Moulton and Richards analysis would be on what is characterized as ''marginal cropland" but which would in fact be very good forestland. The analysis does not include a start-up period for tree planting and establishment but assumes "instant trees" with all establishment costs in the first year.

The structure of the Moulton and Richards report is such that one can examine the program incrementally. Table P.1 shows the implications of planting enough trees—in order of increasing dollars per ton of carbon—to sequester carbon at rates of 10 percent, 20 percent, and 56.4 percent of current U.S. total CO2 emissions. The table shows that at the 10 percent level most of the uptake would be accomplished by changing forest management practices on current forestlands and planting on marginal pasturelands, but that in order to get very much of the maximum potential, large-scale inclusion of marginal croplands would be required.

Recognizing that the Moulton and Richards analysis suggests that 56.4 percent of U.S. CO2 emissions could perhaps be offset with a massive commitment to a reforestation program, the Mitigation Panel adopts a very conservative approach to estimating the carbon offset that might be envisioned. This analysis accepts that the 10 percent objective described by Moulton and Richards is a reasonable initial target and that reforestation of economically marginal or environmentally sensitive pasture and croplands and nonfederal forestlands to a total 28.7 Mha could take place at costs as described in their analysis. The carbon sequestering rate is then divided by 2 to ensure that only carbon that is truly taken into long-term storage is counted. This baseline then suggests that 240 Mt CO2 could be sequestered at costs between $3 and $10/t CO2 (average cost is $7.20/t CO2). Demonstration projects could verify the lower costs and higher targets for total sequestration projected by some.

TABLE P.1 Reforestation Program Costs by Percentage Reduction

Annual CO2 Offset (%/M short tons)

Land Requirement (M acres)

Total Annual Cost (Billion $)

Average Cost ($/t carbon)

5/72

36.9

0.7

9.72

10/143

70.9

1.7

12.02

20/286

138.4

4.5

15.73

30/429

197.6

7.7

17.91

SOURCE: Moulton and Richards (1990).



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