Forests Sourcebook - HCV Resource Network

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Information obtained through RS sources can be less
detailed than intensive fieldwork; ground verification is
usually needed to verify and calibrate the RS data. A
combination of RS data and field work will produce the
most accurate information.
Conducting periodic assessments of the features of interest
or surrogate indicators. Periodicity depends on the
characteristics being monitored. Compliance with
forestry law may only need yearly assessments of the
extent and location of logging activity, while incidence of
fires may need weekly or monthly monitoring.
Effective venues to channel the information to end users
in easy, user-friendly formats such as Web sites, paper
maps, posters, or CDs. Critical information should be
channeled in a speedy manner to allow rapid response
and action.
In many situations, one or several of these ingredients
exist. Many countries have some type of periodic assessment,
or produce maps of reference data (boundaries of
national parks, for instance). However, monitoring requires
a well-thought-out, systematic approach to integrate all
ingredients together in a methodic way. For example, between
1980 and 2000, four maps of forest resources in Indonesia
were produced (1988, 1993, 1996, and 2000); however, they
do not use consistent legends, units, scales, and time frames,
and thus cannot be used effectively for monitoring.
Selecting the monitoring approach. There are many
different applications of forest monitoring and an equally
large number of approaches by which it can be done. For
example, for measuring forest disturbance (selective logging,
for example) and deforestation some methods are
highly manual and others are highly automated. Some
methods work at moderate resolution over large regions of
forests. Many tools were designed using dated ideas, technologies,
and methods.
Selecting the appropriate approach requires that the
goals of the monitoring exercise be clearly articulated (see
box 7.19). Factors to consider include the size of area to
monitor, the level of detail required, budget constraints, and
season of the year (because of cloud cover). 2
Box 7.19
Selecting the Appropriate Approach and Tools
If the goal is to develop a country-scale monitoring
program for deforestation, defined as clear-cuts of 20
hectares and larger, the rate-limiting step is not analytical
methodology or data availability. Terra-MODIS
satellite imagery is free and can perform the function,
and the methods are simple and automated. The limitation
is in training, exercise, and operational demonstration
of the capability.
If the goal is to develop a country-scale monitoring
program for deforestation with clear-cuts of one hectare
and above plus selective logging, the rate-limiting steps
are in both the analytical techniques and satellite data
availability. With the loss of Landsat 7, the available
data are from a 22-year-old Landsat 5 or from more
expensive sources such as the French or Indian space
agencies. This is workable if, and only if, such channels
remain open.
The methods for fine-scale deforestation and logging
monitoring are highly automated in some programs,
such as the one coordinated at the Carnegie
Institution of Washington.a This automated system
currently works well but falls short in mountainous
terrain and with some of the more noisy high-resolution
sensors, and is still being improved for very smallscale
disturbances. This automated system is the only
one to deliver country-scale deforestation and logging
maps, such as the first-ever large-scale deforestation
plus logging map at sub-30 m resolution (see box figure
for the Amazon). The information from this system
can produce both extent and intensity of forest
disturbance, where the latter is defined as the percentage
of canopy opening and surface debris generation.
Remote monitoring of forest damage levels is now
straightforward, if the challenges presented by clouds
and terrain are resolved.
Other groups mostly use manual techniques, resulting
in long delivery times. Most methods produce forest
and nonforest classes in their products. A few produce
more information, such as fractional cover of the
canopy.
In the figure below, showing land cover change in
the Amazon, the medium gray is what the other “stateof-the-art”
technology shows as deforestation (forest
cover change). The dark gray shows what the automated
system reveals—selective logging completely
missed by other widely used RS systems. The dark gray
currently shows a preview of what will be medium gray
in two to four years.
(Box continues on the following page.)
NOTE 7.3: SPATIAL MONITORING OF FORESTS 277