Forests Sourcebook - HCV Resource Network

Assessment (www.millenniumassessment.org). Another
good framework, although still being piloted and not yet
implemented at regional and global levels, is the “Manual
for Environmental and Economic Accounts” (FAO 2004).
Using existing and new methodologies. Advancements
in methodology and technology are a constant phenomenon
in forest monitoring, as evidenced by the advancements
in remote sensing, a particularly useful tool for studying forest
change comprehensively and uniformly across time and
space. Remote sensing multiplies the value of field-plot data
and permits complete, wall-to-wall analyses. Spatial images
from Landsat have been a workhorse for scientists interested
in measuring changes in the distribution and condition of
forests. A number of satellites have come online since Landsat,
several of which are useful for monitoring forests
(USDA 2007). Other advancements in forest monitoring
approaches have been based on imaging radar data, which
works in all weather conditions. Methodological advancements,
too, such as simplifying and automating mapping of
forest disturbances (USDA 2007), have been important.
Older technologies, such as mobile data loggers and
mobile communication, could be more effectively used for
monitoring forest activities. Mobile telephone communication
can serve two purposes: It can increase the safety of
field crews by giving them access to communication in cases
of emergency, while also enabling online data entry to a central
database. Advancements in software, such as GIS 2 , also
offer many possibilities for presentation of results and
improved access to information.
The use of some of the newer technologies is not without
shortcomings. For example, the availability of reference data
for digital image analysis or visual interpretation is one of
the key problems in remote sensing–aided surveys. The
parameters that can be estimated using remote-sensing surveys
often depend on the intensity of the field sampling.
Area of forests, other wooded land, and other land types, as
well as their changes, can be adequately measured with
available remote sensing–aided surveys. In contrast, tree
stem volume and biomass, which are critical variables in
determining the status of the world’s forests, require thorough
field measurements for their estimation. Such limitations
are constantly being dealt with.
Cost of monitoring. Cost is often an important driver in
designing monitoring systems. A frequently asked question
is when and whether satellite imagery–based forest cover
mapping can substitute for forest inventory. Mapping studies
cost less than field work (if the necessary hardware and
software are available); need less planning, smaller teams,
and less broad expertise; are partly independent of weather;
and provide maps as the major product, which are usually
more easily accepted and “marketed” than statistics and
tables with error specifications.
The type of analysis required often influences the cost.
High-resolution images are notably more expensive than
coarse images. Tomppo and Czaplewski (2002) estimated
costs for remote sensing under different resolutions and
sampling options for regional and global surveys using
remote sensing and field data (see tables 7.2 and 7.3). The
costs have since changed significantly, but this information
provides an indication of the differences in costs.
Selection of indicators. Assessing all benefits from
forests over time is complicated, and only feasible if simplifications
and approximations, such as indicators, are
accepted. Several international processes have developed
criteria and indicators for sustainable forest management.
Table 7.2
Example of Number of Images and Estimated Costs for a Remote-Sensing Survey with
Different Resolution and Sampling Options
Number of images needed
Imaging cost (US$ thousand)
MODIS Landsat Ikonos Ikonos Landsat Ikonos Ikonos
full 10% 0.1% 1% 10% 0.1% 1%
Region coverage coverage coverage coverage coverage coverage coverage
Africa 6 97 331 3,309 58 951 8,992
Asia 6 100 343 3,428 60 986 9,315
Europe 4 73 251 2,511 44 722 6,824
North and Central America 4 69 237 2,374 42 683 6,453
Oceania 2 28 94 943 17 271 2,564
South America 3 57 195 1,950 34 561 5,299
Total 25 424 1,451 14,515 255 4,174 39,447
Source: Tomppo and Czaplewski 2002.
Note: MODIS and Landsat are NASA satellite imaging programs; Ikonos is is a commercial Earth observation satellite.
254 CHAPTER 7: MONITORING AND INFORMATION SYSTEMS FOR FOREST MANAGEMENT