Considering Cumulative Effects Under the National Environmental Policy Act Page: 51
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In addition to the primary and special
methods discussed above, there are several
tools that can be used to conduct or illustrate
cumulative effects analysis. The most impor-
tant are modern computers with capabilities for
storing, manipulating, and displaying large
amounts of data. Although simple tables,
graphs, and hand-drawn maps are adequate for
many analyses, powerful computers can facil-
itate the use of multidimensional matrices and
sophisticated models that require solving com-
plex equations or conducting simulations.
General tools for illustrating cumulative effects
include dose-response curves, cumulative fre-
quency distributions, maps, and videography.
Video simulation, wherein an existing site is
captured through imagery and electronically
altered to show how the site will look after a
proposed action is implemented, is a promising
new technology for analyzing effects and com-
municating them to the public (Marlatt et al.
1993).
Most importantly, geographic informa-
tion systems (GIS) can manipulate and dis-
play the location-specific data needed for
cumulative effects analysis. GIS can be used to
manage large data sets, overlay data and
analyze development and natural resource
patterns, analyze trends, use mathematical
models of effect with locational data, perform
habitat analysis, perform aesthetic analysis,
and improve public consultation (Eedy 1995).
GIS can incorporate a statistically reliable
locational component into virtually any cumu-
lative effects analysis. Unlike manual mapping
systems, the scale can be adjusted and the data
layers easily updated. Once a GIS has been
developed, it can drastically reduce the effort
needed to analyze the effects of future projects,
i.e., each new development proposal can be
readily overlain on existing data layers to evalu-
ate cumulative effects (Johnston et al. 1988).Effective use of the increased analytical and
presentation capabilities of computers and GIS
requires large amounts of data. Fortunately,
available remote sensing technologies can
provide locational information at varying levels
of resolution for virtually all parts of the United
States. Remote sensing applications (both pho-
tographic and satellite imagery) can help the
analyst reveal the past status of environmental
resources or ecological processes, determine
existing environmental conditions, and quan-
titatively or qualitatively assess possible future
trends in the environment. Although remote
sensing is a relatively recent technological
development, aerial photography available for
most areas of the United States since the 1930s
or 1940s, and space-based photographs and
satellite imagery have been collected since the
1960s. For example, aerial photography from
1960, 1981, and 1990 (Figure 5-2) show change
in the condition of small mountainous tributary
streams to the North Fork Hoh River in the
Olympic Peninsula. The photo taken in 1960
shows undisturbed old growth Sitka spruce-
hemlock forest. The photos of the same location
taken in 1981 and 1990 show extensive timber
harvest and soil erosion. Each patch of har-
vested timber was approved under individual
logging permits over a 30-year period. As a
result of the cumulative timber harvest, the
area has experienced severe landsliding and
erosion, causing sedimentation in salmon
spawning and rearing areas in the Hoh River
and in lower portions of the tributary streams.
The combination of remote sensing and GIS
has facilitated the development of a suite of
landscape-scale indicators of ecosystem status
that hold promise for quantifying ecological
variables and improving the measurement of
cumulative effects (Hunsaker and Carpenter
1990; Noss 1990; O'Neill et al. 1988, 1994).54
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Council on Environmental Quality (U.S.). Considering Cumulative Effects Under the National Environmental Policy Act, text, January 1997; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc31126/m1/60/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .