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
Summary
7
an effort to plant vegetation along many highways, some of which is selected because it is native to the United States (but not always from the
local area). The linear pathways of continuous terrestrial or aquatic habitat adjacent to roads can serve as corridors for animal movement. Some
animals are attracted to roadside vegetation, road kill (an animal that has
been killed on a road by a motor vehicle), or the light and heat often associated with roads, and other animals are deterred by disturbances in the
road-effect zone.
The ecological effects of building a road typically exhibit several
time lags. Some effects of road construction are not realized until several months or even decades after a road is completed as nearby trees and
other plants slowly die, although the most severe (condensed and sudden) effects typically occur when construction begins. Vegetation reestablishment efforts may result in a quick pulse of plant growth after seeding and fertilization, but the new equilibrium of vegetation along roadsides usually takes some time to establish, particularly in locations with
steep slopes, rocky or nonorganic substrate, or other conditions that encourage roadside erosion.
Although most of the current and foreseeable transportation projects in the United States are along established roads, the increase in traffic volume on these roads and the selection of sites for new roads bring
to the forefront the potential for new ecological impacts―and associated,
often delayed responses of the environment.
Understanding and Assessing Road Effects
As described above, a great deal is known about the ecological effects of roads, even though there is need for more and better information
about cumulative, long-term, and large-scale effects. The available information, much of it reviewed, summarized, and synthesized in this report, should be used in all stages of road building and maintenance, including planning.
From planning through construction stages, ecological indicators
are important in assessing road effects; however, determining the broader
and cumulative effects of roads and their corridors also is important and
often not captured by indicators. Ecological indicators are generally developed to quantify ecological responses to a variety of factors. Several
indicators have been proposed to measure or monitor ecological effects,
and some of them are applicable to the effects of roads.
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
Summary
7
an effort to plant vegetation along many highways, some of which is selected because it is native to the United States (but not always from the
local area). The linear pathways of continuous terrestrial or aquatic habitat adjacent to roads can serve as corridors for animal movement. Some
animals are attracted to roadside vegetation, road kill (an animal that has
been killed on a road by a motor vehicle), or the light and heat often associated with roads, and other animals are deterred by disturbances in the
road-effect zone.
The ecological effects of building a road typically exhibit several
time lags. Some effects of road construction are not realized until several months or even decades after a road is completed as nearby trees and
other plants slowly die, although the most severe (condensed and sudden) effects typically occur when construction begins. Vegetation reestablishment efforts may result in a quick pulse of plant growth after seeding and fertilization, but the new equilibrium of vegetation along roadsides usually takes some time to establish, particularly in locations with
steep slopes, rocky or nonorganic substrate, or other conditions that encourage roadside erosion.
Although most of the current and foreseeable transportation projects in the United States are along established roads, the increase in traffic volume on these roads and the selection of sites for new roads bring
to the forefront the potential for new ecological impacts―and associated,
often delayed responses of the environment.
Understanding and Assessing Road Effects
As described above, a great deal is known about the ecological effects of roads, even though there is need for more and better information
about cumulative, long-term, and large-scale effects. The available information, much of it reviewed, summarized, and synthesized in this report, should be used in all stages of road building and maintenance, including planning.
From planning through construction stages, ecological indicators
are important in assessing road effects; however, determining the broader
and cumulative effects of roads and their corridors also is important and
often not captured by indicators. Ecological indicators are generally developed to quantify ecological responses to a variety of factors. Several
indicators have been proposed to measure or monitor ecological effects,
and some of them are applicable to the effects of roads.