Copyright © National Academy of Sciences. All rights reserved.
This executive summary plus thousands more available at http://www.nap.edu
Assessing and Managing the Ecological Impacts of Paved Roads
http://books.nap.edu/catalog/11535.html
4
Assessing and Managing the Impacts of Paved Roads
There are cases in which the meaning of the term “road density” is
clear, but often it may be difficult to make useful comparisons between
the ecological effects of different types of road networks. For example,
several two-lane roads that have little traffic versus fewer, eight-lane
roads that are heavily traveled. Therefore, the committee focused on
variables that contribute to density, such as highway length and portion
of land covered, rather than strictly on density, and used the broader concept of “scale” for evaluating environmental effects.
The committee focused on the ecological effects of federally
funded paved highways in urban and rural locations. The committee did
not focus on urban street networks, and no consideration was given to the
ecological effects of unpaved roads, such as those found in federal forests, wilderness areas, wetlands, parks, and farms, or the ecological effects of state and local roads. The committee did not address global or
regional climate effects, such as how potential climate changes might
affect the interactions of organisms and the environment associated with
roads and vehicles or how roads and traffic might influence climate.
However, local climate interactions with road ecology are considered in
this report.
Developing policy choices to balance mobility, economic growth,
and environmental protection goals has been important and challenging
for more than 50 years. Although the committee was not charged to
evaluate such policy choices, it identified the ecological effects of roads
that can be evaluated in the planning, design, construction, and maintenance of roads. The committee did not address human ecological factors; nonecological factors, such as safety; efficient movement of vehicles; or protection of farmlands, publicly owned recreation lands, and
scenic, historic, and cultural areas. The committee also did not address
such factors as urban sprawl or suburban growth; project costs; statewide, regional, and local planning goals; and the economic viability of
the communities of users.
ECOLOGICAL EFFECTS OF ROADS
Perhaps the most noticeable ecological effect of roads is direct, vehicle-related mortality (animals killed by collisions with vehicles). Although it is not the most threatening effect of roads for most species,
mortality can reduce wildlife-population densities and ultimately affect
This executive summary plus thousands more available at http://www.nap.edu
Assessing and Managing the Ecological Impacts of Paved Roads
http://books.nap.edu/catalog/11535.html
4
Assessing and Managing the Impacts of Paved Roads
There are cases in which the meaning of the term “road density” is
clear, but often it may be difficult to make useful comparisons between
the ecological effects of different types of road networks. For example,
several two-lane roads that have little traffic versus fewer, eight-lane
roads that are heavily traveled. Therefore, the committee focused on
variables that contribute to density, such as highway length and portion
of land covered, rather than strictly on density, and used the broader concept of “scale” for evaluating environmental effects.
The committee focused on the ecological effects of federally
funded paved highways in urban and rural locations. The committee did
not focus on urban street networks, and no consideration was given to the
ecological effects of unpaved roads, such as those found in federal forests, wilderness areas, wetlands, parks, and farms, or the ecological effects of state and local roads. The committee did not address global or
regional climate effects, such as how potential climate changes might
affect the interactions of organisms and the environment associated with
roads and vehicles or how roads and traffic might influence climate.
However, local climate interactions with road ecology are considered in
this report.
Developing policy choices to balance mobility, economic growth,
and environmental protection goals has been important and challenging
for more than 50 years. Although the committee was not charged to
evaluate such policy choices, it identified the ecological effects of roads
that can be evaluated in the planning, design, construction, and maintenance of roads. The committee did not address human ecological factors; nonecological factors, such as safety; efficient movement of vehicles; or protection of farmlands, publicly owned recreation lands, and
scenic, historic, and cultural areas. The committee also did not address
such factors as urban sprawl or suburban growth; project costs; statewide, regional, and local planning goals; and the economic viability of
the communities of users.
ECOLOGICAL EFFECTS OF ROADS
Perhaps the most noticeable ecological effect of roads is direct, vehicle-related mortality (animals killed by collisions with vehicles). Although it is not the most threatening effect of roads for most species,
mortality can reduce wildlife-population densities and ultimately affect