406
Characterizing the Human Imprint on Landscapes for Ecological Assessment
tributes used in the DLGs to describe transportation features. However, the DLGs are not updated
consistently. For up to date transportation-related
information, transportation departments in various
states are good places to start. The U.S. Department of Transportation (DOT), through its Bureau
of Transportation Statistics (BTS), produces a digital data product called the National Transportation
Atlas Databases (USBTS, 1996), with much of the
transportation-related data mapped at a base scale
of I : 100,000. Many private companies provide
relatively up to date transportation-related information because of the growing demand for realtime vehicle navigation systems.
Research and development needs in this area include expanding the use of GIS network analysis
capabilities in ecosystem assessments. For example, distances, which are often used to describe the
influence that societal structures or features have
on an ecosystem, are often more accurately depicted when based on the transportation network
than using straight-line or Euclidean distance. For
example, the potential of a place to be developed
for residential use is a function of, among other
things, nearness to urban employment centers and
services. The distance perceived by a landowner,
however, has more to do with travel time and distance on the transportation network than with
straight-line distance (i.e., how far from the city as
the crow flies). Distances, therefore, should be calculated along the road network, rather in a straight
line.
27.2.2 Utilities
Utility networks have a topological structure that
is similar to transportation networks, with a primary exception being that flow on the networks is
usually one-way. Utility networks that may be of
interest in an ecological assessment can be placed
into two categories: pipelines (including gas, oil,
water, and sewer) and cables (including telephone,
cable television, and electricity). The direct effects
of the former are more obvious than those of the
latter. Installation of pipelines tends to be more disruptive to an ecosystem, and any break in the network can result in the release of a substantial quantity of polluting substances. In the case of both
types of networks, there is usually some land clearing and maintenance involved along the route of
the network, resulting in some habitat fragmentation. The indirect effects of both types of utility networks are similar to those of transportation networks. Although development can occur in their
absence, it tends to be more rapid in their presence.
As communication links are improved and information flows more efficiently (e.g., with the introduction of fiber-optic cable), rural areas are
increasingly seen as alternative places for development of residential property and remote service
industries.
Attributes of utility networks describe capacity
and actual transmission rates and might be useful
in understanding the potential for indirect influences on ecosystems. These attributes are more
commonly used in automated mapping and facilities management (AMlFM) systems. Such systems,
maintained by utility companies, are the best source
for network data. For this reason there is relatively
little in the way of standardized data over large areas, except for the largest, national-scale pipeline
networks (e.g., the Alaska pipeline).
27.2.3 Land Cover
Although land cover is a general term for that
which covers the soil surface (including vegetation,
litter, water, structures), some specific types ofland
cover (e.g., crops, built-up areas) are more obviously anthropogenic than others. Vegetation is often managed for human use in some manner, and
its pattern might also be viewed as anthropogenic
to some extent. Among the more radical changes
to land cover by humans is the paving of the soil
surface, which interrupts hydrologic and nutrient
cycles and affects microclimate (e.g., the urban heat
island effect). Buildings and other structures have
a similar effect. Urbanized ecosystems, therefore,
tend to function very differently from nonurbanized ecosystems; they tend to have warmer and
more contaminated atmospheres with more rapid
surface runoff. Replacement of natural vegetation
with agricultural crops, orchards, and feed for animals (i.e., pasture) has a range of implications for
these cycles as well. Conversion of wetlands for
agricultural or urban uses can also have drastic effects on ecosystem function, eliminating the
ecosystem services provided by wetlands while altering nutrient cycles for crop production.
Land cover is distinct from land use, which refers
to the way in which the land is managed for human goals. The critical land cover issues address
what is covering the surface at any given point in
time and how that cover affects hydrological, biogeochemical, and biological functions. Different
land uses may lead to different spatial and temporal patterns of land cover, but land use does not
predict land cover perfectly. Regardless, land use
and cover are often mapped together. Anderson et
al. (1976) present a system for use with remotely
Characterizing the Human Imprint on Landscapes for Ecological Assessment
tributes used in the DLGs to describe transportation features. However, the DLGs are not updated
consistently. For up to date transportation-related
information, transportation departments in various
states are good places to start. The U.S. Department of Transportation (DOT), through its Bureau
of Transportation Statistics (BTS), produces a digital data product called the National Transportation
Atlas Databases (USBTS, 1996), with much of the
transportation-related data mapped at a base scale
of I : 100,000. Many private companies provide
relatively up to date transportation-related information because of the growing demand for realtime vehicle navigation systems.
Research and development needs in this area include expanding the use of GIS network analysis
capabilities in ecosystem assessments. For example, distances, which are often used to describe the
influence that societal structures or features have
on an ecosystem, are often more accurately depicted when based on the transportation network
than using straight-line or Euclidean distance. For
example, the potential of a place to be developed
for residential use is a function of, among other
things, nearness to urban employment centers and
services. The distance perceived by a landowner,
however, has more to do with travel time and distance on the transportation network than with
straight-line distance (i.e., how far from the city as
the crow flies). Distances, therefore, should be calculated along the road network, rather in a straight
line.
27.2.2 Utilities
Utility networks have a topological structure that
is similar to transportation networks, with a primary exception being that flow on the networks is
usually one-way. Utility networks that may be of
interest in an ecological assessment can be placed
into two categories: pipelines (including gas, oil,
water, and sewer) and cables (including telephone,
cable television, and electricity). The direct effects
of the former are more obvious than those of the
latter. Installation of pipelines tends to be more disruptive to an ecosystem, and any break in the network can result in the release of a substantial quantity of polluting substances. In the case of both
types of networks, there is usually some land clearing and maintenance involved along the route of
the network, resulting in some habitat fragmentation. The indirect effects of both types of utility networks are similar to those of transportation networks. Although development can occur in their
absence, it tends to be more rapid in their presence.
As communication links are improved and information flows more efficiently (e.g., with the introduction of fiber-optic cable), rural areas are
increasingly seen as alternative places for development of residential property and remote service
industries.
Attributes of utility networks describe capacity
and actual transmission rates and might be useful
in understanding the potential for indirect influences on ecosystems. These attributes are more
commonly used in automated mapping and facilities management (AMlFM) systems. Such systems,
maintained by utility companies, are the best source
for network data. For this reason there is relatively
little in the way of standardized data over large areas, except for the largest, national-scale pipeline
networks (e.g., the Alaska pipeline).
27.2.3 Land Cover
Although land cover is a general term for that
which covers the soil surface (including vegetation,
litter, water, structures), some specific types ofland
cover (e.g., crops, built-up areas) are more obviously anthropogenic than others. Vegetation is often managed for human use in some manner, and
its pattern might also be viewed as anthropogenic
to some extent. Among the more radical changes
to land cover by humans is the paving of the soil
surface, which interrupts hydrologic and nutrient
cycles and affects microclimate (e.g., the urban heat
island effect). Buildings and other structures have
a similar effect. Urbanized ecosystems, therefore,
tend to function very differently from nonurbanized ecosystems; they tend to have warmer and
more contaminated atmospheres with more rapid
surface runoff. Replacement of natural vegetation
with agricultural crops, orchards, and feed for animals (i.e., pasture) has a range of implications for
these cycles as well. Conversion of wetlands for
agricultural or urban uses can also have drastic effects on ecosystem function, eliminating the
ecosystem services provided by wetlands while altering nutrient cycles for crop production.
Land cover is distinct from land use, which refers
to the way in which the land is managed for human goals. The critical land cover issues address
what is covering the surface at any given point in
time and how that cover affects hydrological, biogeochemical, and biological functions. Different
land uses may lead to different spatial and temporal patterns of land cover, but land use does not
predict land cover perfectly. Regardless, land use
and cover are often mapped together. Anderson et
al. (1976) present a system for use with remotely