5.4.1.2. Measurement of Carbon Benefits
Land-use and forestry projects generally are easier to quantify and monitor
than national inventories because of the clearly defined boundaries for project
activities, the relative ease of stratification of the project area, and the
choice of carbon pools to measure (Section 5.4.1.1). Techniques
and methods for sampling design and for accurately and precisely measuring individual
carbon pools in LULUCF projects are based on commonly accepted principles of
forest inventory, soil sampling, and ecological surveys (Pinard and Putz, 1996,
1997; MacDicken, 1997a,b; Post et al., 1999; Winrock International, 1999;
Hamburg, 2000). For example, there is a wealth of experience with well-developed
and accepted methods to inventory forests for merchantable volume and growth;
these methods can be and are being readily adopted to inventory forest biomass
carbon. Likewise with regard to measuring soil carbon, standardized techniques
are well established. Further descriptions of methods for estimating the carbon
pool in live tree biomass, understory and herbaceous plants, roots, fine and
coarse litter, and soil are described in Chapter 2. Standard
methods have not been universally applied to all projects, however, and methods
of accounting for carbon benefits have not been standardized-resulting in some
difficulties in comparing results across different LULUCF projects.
For most LULUCF projects, it would be necessary to measure non-project reference
or control sites as well. These sites must be sufficiently similar to the project
area to serve as valid proxies under the assumption that the project was not
implemented (Vine et al., 1999). To help overcome the difficulty of establishing
proxy areas, non-project reference sites could be identified during the project
design phase. The location of proxy sites as close as possible to the project
would be the most desirable situation. For example, in projects in which many
small landowners convert to no-till agriculture, proxy areas would be farmers
in the area who do not practice no-till agriculture. Box
5-3 illustrates the types of measurements being taken to estimate with-
and without-project cases and the resulting carbon benefits.
The total carbon stock has been measured to <10 percent of the mean with 95-percent
confidence in several pilot LULUCF projects (e.g., Programme for Belize, 1997a;
Hamburg, 2000; NKCAP-see Box 5-3). Although techniques
and tools exist to measure carbon stocks in project areas to a high degree of
precision, the same level of precision for carbon benefits may not be achieved.
The carbon benefit per unit area of land is the difference between the carbon
stocks in the with-project case-which is high if, for example, the project is
conserving carbon in existing forests through an avoided deforestation project-and
the carbon pools in the without-project case, which is low if the baseline is
agricultural or degraded lands. In this case, the estimated carbon benefit is
likely to be high (a small carbon stock subtracted from a large carbon stock),
and the error estimate, expressed as a percentage of the mean difference, likely
to be small and similar to that obtained for carbon stocks in the forests. As
the difference between the with- and without-project cases decreases as, for
example, in reduced impact logging projects, however, the percentage error of
the carbon benefit increases. To reduce this error, monitoring can be designed
to measure the change in carbon stocks directly, as in the NKCAP (see Box
5-3). Difficulties in establishing baselines and leakage effects also affect
the precision of the carbon benefits.
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