Introduction

Roads are pervasive features of modern

landscapes and have major impacts on air, land,

and water quality. The United States has >6.2

million km of public roads used by >200 million vehicles (National Research Council

[NRC]1997). Road corridors (road plus maintained parallel strips) cover 1% of the United

States (NRC 1997) but their direct environmental impacts extend to 20% of the land

surface (Forman 2000). Ecological effects

extend 100 to 1,000 m (average of 300 m) on

each side of four-lane roads (Forman and

Deblinger 2000). These effects, which stem

from both construction and use, vary considerably in type and degree among regions and

among particular roads (Forman and

Alexander 1998; Trombulak and Frissell 2000).

Roads strongly affect the composition and

operation of surrounding ecosystems. Natural

habitats such as forests, wetlands, and streams

are commonly disfigured, fragmented, or contaminated because of roads (Forman and

Deblinger 2000; Trombulak and Frissell 2000;

Paul and Meyer 2001). Effects on biotic populations and communities can be dramatic

and extensive. Major direct effects on wild

animals include modified behavior, impaired

movement, and mortality from collisions

with vehicles (Trombulak and Frissell 2000).

Forman and Deblinger (2000) estimated that

effects on large mammals, birds, and amphibians typically extended to 300 m on both

sides of a four-lane highway in Massachusetts.

In addition, key ecological processes, including the transport of water and sediment and

the dispersal of organisms, are modified by

roads (Forman and Deblinger 2000;

Trombulak and Frissell 2000). 

Despite the increasing prominence of roads

across most landscapes, their impacts on

aquatic biota are not well documented.

Intuitively, effects on water quality (e.g., via

toxic spills and runoff), habitat quality (via

sediment loading and channel modification),

and habitat connectivity (via barriers to movement) may often be severe. Roads may

constrain fish distribution and abundance or

impair ecosystem health. Many road crossings

over streams constrain movements by small

fishes (Warren and Pardew 1998). Such movements are essential for individuals to complete

their life cycles and for metapopulations to

remain viable (Schlosser and Angermeier

1995). To the extent that roads contribute to

fine-sediment loading in waterways, they are

serious threats to aquatic biota (Waters 1995;

Wood and Armitage 1997). Roads are known

to endanger 94 species across many taxa in the

United States (Czech et al. 2000) and probably contribute to local extirpation and regional

endangerment of many fishes. Managers of

fishes and fisheries should be keenly interested

in the environmental impacts of roads, especially proposed roads.

Assessing environmental impacts of

human activities on public resources is an

iterative collaboration among the public,

resource managers, and scientists. Roles of the

public include articulating the impacts of

concern (e.g., through legislation) and hold19

Paul L. Angermeier 

Andrew P. Wheeler

Amanda E. Rosenberger

Angermeier is assistant unit

leader—Fisheries, U.S. Geological

Survey, Virginia Cooperative Fish and

Wildlife Research Unit 2, Virginia

Polytechnic Institute and State

University, Blacksburg. He can be

reached at biota@vt.edu. Wheeler is

an assistant fisheries biologist at the

North Carolina Wildlife Resources

Commission, Waynesville.

Rosenberger is a post-doctoral

researcher at the Rocky Mountain

Research Station, Department of

Civil Engineering, University of

Idaho, Boise. 

featurefish habitat

A Conceptual Framework for Assessing

Impacts of Roads on Aquatic Biota

Roads are pervasive in modern landscapes and adversely affect many aquatic ecosystems.

Conventional environmental assessments of roads focus on construction impacts but

ignore subsequent impacts. A comprehensive framework for considering all impacts of

roads would enable scientists and managers to develop assessment tools that more accurately inform stakeholders and policymakers about the biological consequences of road

building. We developed a two-dimensional framework to organize impacts of roads on

aquatic biota. One dimension recognizes three phases of road development, each with

distinctive ranges of spatial and temporal scales. The second dimension recognizes five

classes of environmental impacts associated with road development. The framework is

useful in evaluating the completeness of assessments and in identifying gaps in scientific

knowledge. We applied the framework to a draft environmental impact statement (DEIS)

for a proposed interstate highway to illustrate which road impacts are typically ignored

in such assessments and how our framework can be used to enhance assessments. The

DEIS largely omitted long-term, large-scale impacts from consideration. Such omissions

preclude fair assessments of the desirability of roads and bias landscape-management

decisions in favor of road building. Additional scientific input and changes in agency ideology are needed to reduce bias in assessments of the biological impacts of roads.

ABSTRACT

December 2004 | www.fisheries.org | Fisheries
ing managers accountable for assessing those impacts.

It is incumbent on managers (often agencies) to

implement specific policies and protocols that

address societal concerns. This process includes seeking out and applying the best available scientific

knowledge and methods to aid in assessing impacts.

Implicit in their contract with society, scientists are

obligated to develop concepts and methods relevant

to societal concerns and to make them available for

managers to apply. All three parties must participate

actively for environmental impact assessments to

serve as intended in the decision-making process. 

Current assessments of environmental impacts of

roads are inadequate to ensure informed decisionmaking (Atkinson and Cairns 1992; TRB 2002).

Transportation policy in the United States is attentive to stream-channel geometry and soil erosion

during road construction but largely ignores many

other common consequences of roads for habitat

quality, ecological processes, and biota (NRC 1997).

In particular, the extensive and serious impacts of

post-construction maintenance and of subsequent

urban development along roads typically are

excluded from agency decisions about building new

roads. Thus, direct, localized, or acute impacts are

emphasized whereas indirect, dispersed, or chronic

impacts are neglected. This bias reflects the typical

application of the National Environmental Policy

Act (NEPA), wherein attention is narrowly focused

on species rather than ecosystems, on site-specific

scale rather than regional scale, and on short-term

rather than long-term environmental impacts

(Southerland 1995), despite the fact that the NEPA

requires all reasonably foreseeable impacts to be

assessed (Council on Environmental Quality [CEQ]

1993). The mismatch between scales of assessment

and impact is especially problematic for roads

because there is compelling scientific evidence that

long-term, large-scale impacts are the greatest threats

to biota. The problem of incomplete assessments of

road impacts has been apparent throughout the 14

years that one of us (PLA) has consulted with the

Virginia Department of Transportation (VDOT) and

the U.S. Fish and Wildlife Service regarding effects

of roads on imperiled fishes in Virginia.

This problem of incomplete assessments became

more obvious and captured our attention when we

recently reviewed VDOT's draft environmental

impact statement (DEIS; VDOT 2000) for the proposed construction of a new interstate highway

(I-73) through Virginia. We judged the DEIS to be

inadequate in its assessment of impacts on the federally endangered Roanoke logperch (Percina rex) as

well as more general impacts on ecosystem integrity

(Wheeler et al. 2003). We suspect that such inadequacy is typical of assessments of road impacts. Our

main concern is that omission of major impacts from

official environmental assessments like this one precludes a fair evaluation of the actual costs of a new

road, biases landscape-management decisions toward

more road-building, and thus results in multiple failures to meet goals of the Endangered Species Act and

the Clean Water Act.

Aquatic scientists as well as resource management

agencies are culpable for inadequate assessments of

road impacts. The lack of appropriate assessment

tools contributes to the inadequacy of environmental

assessments of roads (TRB 2002). The CEQ (1997)

has informally outlined eight general principles and

many steps useful in analyses of cumulative effects of

projects such as roads, but legally binding requirements and an ecological framework for organizing

such analyses are lacking. The DEIS for I-73 was

based on a very narrow conception of what constitutes environmental impact and of the

spatiotemporal frames in which impact is assessed.

Perhaps that conception would have been broader if

ecologists had provided a straightforward framework

to facilitate a more comprehensive assessment of road

impacts on aquatic environments. For example, a

more complete view might recognize that impacts:

(a) occur over multiple spatial and temporal scales,

which reflect the overall process of road development, and (b) can be stratified into physical,

chemical, and biological categories, which differ in

their relative importance at various points in the road

development process. A framework incorporating

these features would provide a basis for gathering a

richer array of relevant information and would enable

managers to readily assess the completeness of their

impact assessments. Because no such framework has

been developed, many impacts, especially long-term

and large-scale impacts, can be easily overlooked by

managers and the public.

Our goal in this article is to present a comprehensive conceptual framework for considering impacts of

roads on aquatic biota. First, we introduce a simple

two-dimensional matrix of impact categories to organize and evaluate the myriad aquatic impacts

associated with roads. The matrix columns reflect

three major phases of road development, each of

which generates impacts at a distinctive range of spatiotemporal scales. The matrix rows reflect five major

classes of physical, chemical, and biological impacts

associated with each development phase. Based on

our review of the scientific literature, we rank each of

the 15 cells in the matrix (three phases x five classes)

with respect to the severity of associated impacts.

Next, we draw from our experience with the I-73

DEIS to illustrate general shortcomings of conventional assessments of road impacts in the context of

our framework. Finally, we discuss how our framework might be used to redress some of these

shortcomings. This discussion is illustrative rather

than prescriptive; developing a detailed protocol or

methodology to evaluate impacts of roads is beyond

the scope of this article. We do not thoroughly review

road impacts (see Forman and Alexander 1998,

Trombulak and Frissell 2000, and Spellerberg 2002

for previous reviews), but do offer examples from the

United States to illustrate types of impacts repre20 fish habitat feature

Fisheries | www.fisheries.org | vol 29 no 12
sented in the framework. Although we emphasize

paved roads, we suspect that the issues we address and

the conclusions we draw also apply to most unpaved

roads. We expect the framework to be most useful in

identifying gaps in environmental impact assessments

as well as gaps in scientific understanding of impacts.

Although we focus on impacts to fishes, the framework is designed to apply to all aquatic biota.

Matrix Columns: 

Phases of Road Development

A crucial step in assessing biotic impacts of roads is

recognizing that road development is a long-term process and that roads affect environmental conditions

over a broad range of spatial and temporal scales. Our

review of the literature suggests three main phases of

road development, each with a distinctive but cumulative suite of environmental impacts road

construction, road presence, and urbanization. Each

phase features a distinctive spatial and temporal frame

over which aquatic biota are affected (Figure 1),

although individual roads vary widely in the details of

particular impacts and spatiotemporal frames. Below,

we provide a brief overview of each phase and describe

general patterns of environmental impacts.

Phase 1: Road Construction

Road construction is characterized by relatively

small temporal and spatial frames (days to years, hundreds to hundreds of thousands of square meters,

respectively; Figure 1). Environmental impacts of

construction largely stem from direct, localized, and

acute alterations of physical conditions, including

addition of fine-sediments, channelization of streams,

and disruption of groundwater flow. Soil erosion associated with construction diminishes rapidly as

exposed areas are revegetated and stabilized

(Ketcheson and Megahan 1996). 

Construction activities can affect aquatic biota

directly and indirectly. Operating machinery in shallow-water habitats can destroy nests of animals or

crush sedentary individuals (e.g., mollusks). The

most serious and common biotic impacts of road construction stem from the indirect effects of elevated

levels of fine sediment. Excessive fine sediment interferes with breathing, feeding, reproducing, and food

production for many aquatic animals (Waters 1995;

Wood and Armitage 1997). Consequently, sediments generated during construction can

substantially depress certain populations of invertebrates (e.g., Cline et al. 1982) and fishes (e.g.,

Whitney and Bailey 1959), thereby producing communities dominated by silt-tolerant species.

Reducing the impact of fine sediment generated by

road construction is the principal focus of mitigation

measures employed by transportation agencies during

construction projects (Southerland 1995). For example, the VDOT regularly imposes restrictions on the

seasons during which construction can occur and

authorizes translocation of sedentary animals from

construction sites. However, even though effects of

construction-generated sediment may extend several

km beyond the construction site and persist for years

after construction, large-scale and long-term effects

rarely are assessed or studied (but see Wellman et al.

2000).

Phase 2: Road Presence

We view roads passing within 1 km of a water

body as being ecologically "present." Of particular

concern are roads that cross or have a direct hydrological connection to a water body. Road presence

affects aquatic systems over similar spatial frames but

larger temporal frames (decades to centuries), compared to road construction (Figure 1). The longer

timeframes reflect the fact that few roads are ever

restored to natural habitat. Physical impacts of road

presence include intermittently recurring effects of

maintenance construction (short-term effects), as

well as the long-term potential for alterations in

stream hydrology and geomorphology. Hydrological

effects of roads at the scale of whole watersheds are

scarcely studied. However, studies in the Pacific

Northwest show that roads increase the magnitude

and frequency of floods and debris flows, and ultimately may increase the extent of stream networks

(Jones et al. 2000). Thus, many roads may be major

sources of sediment throughout their existence. 

In addition to physical effects of road presence,

there is a suite of acute and chronic chemical effects

associated with maintenance activities and vehicular

traffic. Deicing salt is commonly applied to roads and

eventually enters waterways, where it can dramatically alter ion concentrations (Koryak et al. 2001) or

add heavy metals (Oberts 1986). During runoff

events, traffic residues produce a contaminant "soup"

of metals, oil, and grease, some of which accumulates

in stream sediments (e.g., Van Hassel et al. 1980) or

disperses into groundwater (e.g., Van Bohemen and

Janssen van de Laak 2003). Sublethal effects (e.g., on

behavior, growth, or reproduction) of such contaminants seem likely but are largely unknown. Toxic

spills are inevitable, potentially catastrophic impacts

of large roads. Most hazardous materials, of nearly all

types, are transported by truck in the United States

21

Figure 1. Temporal and

spatial extent of biotic

impacts due to the three

main phases of road

development. Road

construction occurs over

relatively small time and

space scales, while

urbanization occurs over

much larger scales. Note

logarithmic scaling of axes. feature fish habitat

December 2004 | www.fisheries.org | Fisheries

1000

1

.001

0.1 1 10 100

Duration (years)

Spatial Extent (Sq.-KMs)

Road construction

Urbanization

Road presence
(Atkinson and Cairns 1992). Over 10,000 accidental

releases of hazardous material occur annually on

highways in the United States (USEPA 1996); many

of these materials eventually reach waterways and

devastate local biota.

The biological consequences of road presence are

poorly documented. Several studies have shown elevated concentrations of contaminants in aquatic

animals near roads (Van Hassel et al. 1980;

Stemberger and Chen 1998) but effects on populations and communities are largely unexamined.

Roads enhance human access to water bodies,

thereby increasing the spread of non-native fishes

(e.g., via authorized and unauthorized stocking),

mollusks, and pathogens (Trombulak and Frissell

2000). Many roads fragment aquatic habitats at culverts, which can be significant barriers to fish

movement (Warren and Pardew 1998; Wellman et

al. 2000). Although poorly documented, such barriers could impair recolonization after local extinctions

or reduce gene flow. The lack of extensive roadless

areas in the United States makes scientific study of

road impacts on biota very difficult. Nevertheless, we

hypothesize that road density is correlated with

increasing predominance of species tolerant to silt,

metals, petroleum products, and salt. In areas with

frequent toxic spills, predominant species must also

be good colonizers. Unfortunately, none of these biological effects of road presence was discussed in the

DEIS for I-73.

Phase 3: Urbanization

Urbanization, the final phase of road development, affects aquatic systems across large spatial and

temporal frames (up to thousands of square kilometers and centuries respectively; Figure 1).

Urbanization, the general transformation from rural

or agricultural to residential, commercial, or industrial land use, has accelerated in recent decades and

is a major contributor to contamination of surface

and ground water and to modification of hydrology in

the United States (USEPA 2000). Over 130,000 km

of U.S. streams and rivers are impaired by urbanization, making it a leading cause of water-body

impairment (USEPA 2000). Moreover, urbanization

endangers at least 275 species in the United States,

where it is the second-leading cause (next to nonnative species) of species imperilment (Czech et al.

2000). 

The relation between road building and urbanization is noteworthy in the context of road impacts on

aquatic biota because it is typically ignored in official

impact assessments. This omission is puzzling in

NEPA-driven assessments (required for all federally

funded projects), given that highway projects are one

the main types of federal action that cause urban

sprawl (Southerland 2004). Effects of urbanization,

which may lag behind road construction for decades,

are generally excluded from impact assessments

despite their severe, well-documented consequences

for biota. More explicit recognition of the relation

between road building and urbanization and of the

effects of urbanization on aquatic biota is crucial to

comprehensive assessment of road impacts. Roads,

especially highways, are necessary but not sufficient

for economic growth (TRB 1995). Although specific

effects of new highways on land development patterns

are poorly understood (TRB 2002), roads unquestionably facilitate urbanization, including more road

building, through their strong influence on the distribution of development (TRB 1995). Although roads

are not the sole determinants of economic growth,

many highways are built for the express purpose of

promoting it. For example, the U.S. Congress authorized building the Appalachian Development

Highway System, a 5,535-km network of major highways, to promote economic development in

Appalachia. This network, which is 75% complete,

has contributed substantially to the region's economic

growth (Wilbur Smith Associates 1998). In rural

areas, where new highways tend to be built, economic

growth is tantamount to urbanization. In some mountainous areas of the eastern United States, roads and

urban sprawl generally follow stream valleys (Wear

and Bolstad 1998), resulting in especially severe

impacts on aquatic biota. 

Urbanization affects aquatic ecosystems in many

ways (see Paul and Meyer 2001 for a review of effects

on streams). Physical and chemical effects of urbanization include all those of road construction and road

presence, but are more severe because of greater road

densities, more construction, and more vehicular traffic in urban areas. For example, urbanizing watersheds

can contribute 10,000 times as much fine sediment to

streams as forested watersheds (Wolman and Schick

1967). Urban streams also carry higher concentrations of phosphorous and nitrogen than forested or

agricultural streams (Osborne and Wiley 1988).

An additional suite of physical effects on streams

emerges in urbanized watersheds in response to

hydrologic changes. The proliferation of impervious

surfaces fundamentally alters the timing of precipitation runoff, resulting in higher peak flows during

storms and lower base flows (e.g., Wang et al. 2001).

Roads are often the biggest contributor to impervious

area (May et al. 1997). The increased flood frequency

causes stream channels to incise (Booth 1990),

which may add additional fine sediment to bottom

substrates. Consequently, urban streams tend to have

deep, wide, silty channels with relatively little water.

Although stream channels may naturally adjust to

the altered hydrology, such adjustments may take several decades following urbanization (Henshaw and

Booth 2000).

Habitat quality in urban streams is often further

reduced by active removal of instream woody debris

and riparian vegetation. Woody debris is crucial in

providing cover for fishes and substrate for invertebrates, and as an agent of pool formation. Vegetation

along streams is a key source of organic matter,

22 fish habitat

feature

Fisheries | www.fisheries.org | vol 29 no 12
including wood, which supports food webs and biotic

production. Riparian vegetation buffers streams from

inputs of contaminants and fluctuations in temperature and flow (May et al. 1997). Riparian vegetation

and large woody debris also help stabilize stream

banks and channels.

The physical and chemical changes associated

with urbanization strongly influence aquatic biota.

Fish abundance often decreases as urbanization

increases (Weaver and Garman 1994; Wang et al.

2000). Populations that persist in urban ecosystems

must be tolerant to all the insults associated with road

construction and presence, as well as to extreme variation in water flow, temperature, and food

availability. Consequently, macroinvertebrate and

fish communities in urbanized watersheds commonly

exhibit low species and functional diversity (Weaver

and Garman 1994; Kemp and Spotila 1997).

Anadromous fishes are especially sensitive to urbanization (Limburg and Schmidt 1990). Although

specific mechanisms are not well understood, biotic

impacts are detectable quite early in the urbanization

process. Tolerant macroinvertebrate and fish species

quickly replace sensitive species as impervious surfaces cover 5–15% of a watershed's area. Biotic

communities often change little after impervious

land cover exceeds 20% of a watershed (Booth and

Jackson 1997; Wang et al. 2000; but see Morley and

Karr 2002 for a biotic response when impervious land

cover exceeds 50%). Thus, unlike most agricultural

land cover, small amounts of urban land cover, especially near streams, can severely impair biota (Wang

et al. 2001). Additional study is needed to sort out

the relative importance of physical versus chemical

effects as the primary drivers of biological changes

during urbanization.

Viewing road development in three progressive

phases provides a simple framework for organizing the

broad range of spatial and temporal scales over which

biota are affected by roads. The three phases can

serve as one dimension in categorizing the types of

impacts that resource managers might need to assess.

Each phase is associated with a distinctive suite of

physical, chemical, and biotic effects; some effects in

each phase are often severe. Ecologically organized

categories for these effects would complement the

phases of road development and serve as a second

dimension in a framework for assessing road impacts.

We suggest five such categories in the next section. 

Matrix Rows: 

Classes of Factors 

Affecting Biota

For environmental impact assessments to be useful in public decisions, the assessors must clearly

address the environmental concerns of society. These

concerns are articulated in cornerstone pieces of federal legislation such as the Clean Water Act, which

explicitly mandates the protection of aquatic biological integrity. This mandate provides an appropriate,

well-established foundation for assessing impacts of

roads on aquatic biota, where impacts are departures

from the range of natural conditions for a given

region. Important strengths of the integrity concept

are that it applies to multiple levels of biotic organization (e.g., individual, population, community) and

a wide range of spatiotemporal scales (Angermeier

and Karr 1994). Incorporating biological integrity

into assessments of road impacts will yield assessments that are more comprehensive and public

decisions that are more informed.

The major determinants of biological integrity in

aquatic ecosystems are commonly represented as five

classes of factors: habitat structure, water chemistry,

flow regime, energy source, and biotic interactions

(Angermeier and Karr 1994; Karr and Chu 1998).

Habitat structure encompasses physical features such

as water depth, current velocity, and substrate composition, which form the habitat matrix in which

aquatic organisms live. Water chemistry comprises

parameters such as pH, dissolved oxygen, and contaminant concentrations. Flow regime refers to

temporal patterns in the availability of water, especially seasonal and annual variability. Energy source

encompasses aspects of size, abundance, and nutritional quality of food particles. Biotic interactions

include competition, predation, and parasitism. These

five classes provide an ecological framework for organizing the long lists of specific physical, chemical, and

biological effects of roads. Moreover, based on our

review of the scientific literature, we hypothesize that

roads differentially and predictably influence classes of

factors throughout the process of road development.

To illustrate, we briefly summarize below typical

trends in how these classes of factors are affected in a

water body near to and downstream of a four-lane

highway during the three phases of road development.

The primary impacts of road construction are

linked to earth-moving, which directly alters stream

channel morphology and indirectly accelerates finesediment loading by exposing soils to erosion. These

alterations are manifest as shifts in descriptors of

habitat structure such as channel depth, pool-to-riffle

ratio, percent fines in substrates, and cover availability (Figure 2). Effects on the other four classes of

factors are typically minor and localized.

Effects on habitat structure decrease somewhat

during the road presence phase but effects on water

chemistry and flow regime increase substantially

(Figure 2). Changes in water chemistry commonly

associated with contaminants from roads include elevated concentrations of salt, metals, and petroleum

products. Toxic spills from trucks could cause catastrophic changes in various water-chemistry

parameters. The extensive impervious surface of a

highway would increase the frequency and magnitude of floods. If these increases were large, habitat

structure (e.g., channel depth, percent fines) could be

23

featurefish habitat

December 2004 | www.fisheries.org | Fisheries
affected. Although effects on energy source and

biotic interactions are not expected to be large, they

may become apparent during the road presence

phase. Removal of riparian trees and shrubs, which

often begins during road construction, may reduce

the availability of coarse particulate organic matter

and the ratio of allochthonous-to-autochthonous

production. Introduced non-native species could

cause shifts in the distribution, abundance, or size of

native species.

Road impacts generally increase in severity and

scope throughout the road development process.

Urbanization strongly affects all aspects of aquatic

ecosystems (Figure 2) and undermines biotic

integrity more severely than the other phases of road

development. Moreover, because the ecological

effects of urbanization extend well beyond the immediate vicinity of roads, this is the phase most likely to

threaten entire aquatic populations and communitytypes. Habitat evaluations in urbanized waterbodies

are likely to reveal reduced spatial complexity,

increased embeddedness of substrates, and unstable

streambanks. A wide assortment of contaminants,

including oil, metals, and pesticides, may impair

quality of water and sediment. The hydrology of

urban watersheds is likely to feature frequent and

severe floods and low-flows, with reduced recharge of

groundwater. Urban waters are typically eutrophic

with simple food webs. The resulting biotic communities usually support higher proportions of

non-native species and of native ecological generalists, all of which must be tolerant of poor water

quality and frequent disturbance. 

Applying the Conceptual

Framework

Collectively, the three phases of road development and five classes of ecological factors form a

tractable framework for organizing impacts of roads

on aquatic biota. The framework can be depicted as a

15-cell matrix, where each cell's relative importance

reflects the magnitude of expected effects shown in

Figure 2. For simplicity, we assigned one of two ranks

(high versus low impact) to each cell (Figure 3).

These ranks provide a basis for prioritizing attention

to monitoring, mitigation, or restoration efforts, as

might be needed to meet the goals of the Clean

24

Figure 2.

Hypothesized

size of effects

of road

development

on five classes

of factors that

determine

biotic integrity

of aquatic

ecosystems.

The size of

overall effects

on biotic

integrity also

is shown. fish habitat feature

Fisheries | www.fisheries.org | vol 29 no 12

Habitat structure

Water chemistry

Flow regime

Energy source

Biotic Interactions

Overall Integrity

Large

Small

Large

Small

Large

Small

Large

Small

Large

Small

Large

Small

Effect size

Construction Presence Urbanization

Road development
Water Act or the Endangered Species Act. For example, protecting a stream's biological integrity or

imperiled species would dictate paying more attention to the impacts of road presence or urbanization

than to the impacts of road construction, and more

attention to impacts on habitat structure, water

chemistry, and flow regime than to impacts on energy

source and biotic interactions (Figure 3).

Cell ranks are effectively working hypotheses

based on best available scientific information. Our

cell ranks (Figure 3) reflect our collective best

guesses, and warrant additional rigorous evaluation.

Ideally, sound scientific information would support

the ranks in every cell. In reality, the information

available for cells will vary widely in how confidently

it can be applied to a given road, and may come from

studies of the road in question, studies of other roads,

and expert opinion. The science that informs some

cells (perhaps most) will necessarily be uncertain and

come from inferences based on weights of evidence

(Holling and Allen 2002) rather than from readily

interpreted experimental studies. In any case, compiling the information relevant to each cell for each

assessment is crucial to the general utility of this

framework and to the cost-effective protection of

aquatic biota. Despite the uncertainty of some of the

information supporting cell ranks, we believe that

impact assessments based on such a framework would

provide a much broader knowledge base for informing decision-makers and stakeholders about the

biological consequences of building roads than do

conventional assessments. 

We view our matrix as one of many tools that can

be used to conceptualize and analyze environmental

effects of roads (CEQ 1997). We expect it to be especially useful in scoping ecological consequences and

in gauging the thoroughness of a given impact assessment. The I-73 DEIS that we reviewed appeared

seriously incomplete because the impacts associated

with only 2 of the 15 cells (and only 1 of the 8 highimpact cells) were addressed (Figure 3). A more

appropriate assessment would have reviewed the scientific literature on the effects of roads on (a)

Roanoke logperch (and closely related species), (b)

biotic integrity of streams generally, and (c) other key

resources (e.g., wetlands), then discussed those effects

in the context of all 15 cells in our matrix. The DEIS

discussed impacts on habitat structure and water

chemistry during road construction but neglected all

other impacts. This pattern is especially troubling

because the I-73 DEIS appeared to follow standard

Federal Highway Administration (FHA) guidelines

for such documents. We suspect that most assessments of environmental impacts of roads are similarly

superficial. In fact, there are several reasons to expect

the I-73 DEIS to be more comprehensive than most.

For example, the huge social, economic, and environmental costs of a new interstate and the potential

impacts on federally endangered species should provide strong incentives for a thorough assessment.

Given that the U.S. Environmental Protection

Agency recently lauded the VDOT as "a model of

environmental leadership" (VDOT 2003), VDOT's

investment in environmental assessments seems well

within the range of what is expected of a road management agency. The sharp contrast between the

scope of an impact assessment based on our framework (i.e., with all 15 cells addressed) and the scope

of an actual assessment for a proposed interstate suggests that current standards for environmental

management by road agencies are too low to ensure

protection of aquatic biota. 

The inadequacies we observed in the I-73 DEIS

reflect failures by both managers and scientists. The

authors of the DEIS based their assessment of impact

primarily on unpublished reports rather than on peerreviewed literature, and on a narrow conception of

what constitutes environmental impact. However,

the scientific literature does not provide a useful

framework for conducting comprehensive assessments of road impacts on aquatic environments.

Consequently, many impacts can be overlooked easily by managers and stakeholders. Current

approaches to environmental management recognize

the need for explicit analysis at multiple spatial and

temporal scales and for making the scale at which

management occurs commensurate with the scale of

human impact: (Fausch et al. 2002). The severity and

extent of road impacts warrant assessments more

complete than those traditionally conducted, including more attention to large-scale and long-term

effects. Adopting our framework could help road

managers develop more comprehensive assessments

of road impacts on aquatic biota. For example, assessments might be structured so that each cell in our

matrix is addressed in its own section of text.

Our framework may also be useful in identifying

important gaps in the scientific knowledge germane

to road impacts. Even if managers did adopt our

impact matrix to organize their assessments, the scientific literature pertinent to some cells would be

disconcertingly sparse, especially for post-construction impacts and biotic interactions. Thus,

ecologists need to do a better job of calling attention to the importance of road impacts for aquatic

biota by conducting and publishing studies that

demonstrate impacts at individual, population, and

community levels of organization. Our review of the

literature identified several gaps in scientific

knowledge that cut

across cells in our

impact matrix and warrant additional study

(Table 1). The ranks

(high versus low)

assigned to the cells in

our matrix are effectively hypotheses about

the magnitude of variDecember 2004 | www.fisheries.org | Fisheries 25

Construction Presence Urbanization

Habitat

structure H L H

Water

chemistry L H H

Flow 

regime L H H

Energy

source L L H

Biotic

interactions L L H feature

fish habitat

Figure 3. Hypothetical

matrix of road impacts

that could be used to

scope potential impacts or

to evaluate completeness

of impact assessments.

Cells are ranked as high

(H) or low (L) likelihood of

significant impacts

occurring. Assigned ranks

would be based on regionspecific conditions. The

two cells addressed in the

I-73 draft environmental

impact statement are

indicated by bold letters. 
ous impacts. A major goal of the science related to

road impacts, including research and monitoring,

should be to distinguish confidently between highand low-impact cells. Generating the relevant

knowledge will require scientists and managers to

take fuller advantage of rural areas where additional

road-building is imminent and to create areas where

road removal is politically feasible. Both scenarios

could provide valuable experimental opportunities

to learn about biotic responses to roads. Other

opportunities to build scientific knowledge could

come from experimental studies of the efficacy of

the many protective and restorative measures available to agencies. In all cases, knowledge of

long-term and/or large-scale relations would be

especially valuable. However, building reliable

knowledge will require a much greater fiscal and

philosophical commitment to scientific assessment

of road impacts than is currently in force. 

Socio-political Constraints 

We observed a major discrepancy between the

greatest threats posed by I-73 and the focus of its

DEIS. In particular, threats to Roanoke logperch

and ecosystem health stemmed primarily from

long-term, large-scale effects, especially those due

to urbanization, but the DEIS addressed only certain short-term, small-scale effects of road

construction. This discrepancy reflects the range of

interpretations available for what constitutes biological threat in the context of official impact

assessments and underscores the inadequacy of conventional interpretations for protecting aquatic

biota. Interpretations of "threat" have important

consequences for how legislation is implemented.

For example, under Section 7 of the Endangered

Species Act habitat impairment associated with

roads is usually considered "incidental take" (unintended harm). Incidental take during road

construction is minimized via time-of-year restrictions and implementation of various "best

management practices," but incidental take during

the more harmful post-construction phases of road

development typically is not addressed. A more

comprehensive interpretation of threat and management of the associated incidental take would

enable more effective conservation of imperiled

species. However, the process of defining threat and

impact for regulatory purposes is driven more by

politics than by science.

The narrow focus maintained by state and federal agencies on short-term, small-scale impacts

reflects a broader fundamental problem with the

implementation of environmental policy in the

United States. Several federal laws, including the

Federal-Aid Highway Acts, the Intermodal Surface

Transportation Efficiency Act, and the

Transportation Equity Act for the 21st Century,

call for systematic consideration of social, economic, and environmental impacts of roads and for

more public engagement in transportation planning (TRB 2002). States have much flexibility in

satisfying these mandates but traditionally have

given environmental concerns less weight than

short-term economic and political priorities in

highway-planning decisions (Atkinson and Cairns

1992). The NEPA requires agencies that use federal

funds for road-building to develop EISs that consider all reasonably foreseeable environmental

effects, including direct and indirect effects (FHA

2002). Because little formal federal oversight has

been provided (e.g., by the CEQ), agencies independently have developed protocols for analyzing

cumulative effects of roads (CEQ 1997).

Unfortunately, a consistent pattern is that "road

impacts" have been constrained to mean "road construction impacts" in the context of NEPA

implementation. Effects of road construction are

viewed as direct effects, whereas effects of road

presence and urbanization, although quite foreseeable, are relegated to indirect (or secondary)

effects. Thus, agencies generally abrogate their

responsibilities to address environmental consequences beyond the actual building of roads.

Although many experts agree that environmental assessments of new highways should include

direct, indirect, and cumulative effects (Atkinson

and Cairns 1992; FHA 2002; TRB 2002), progress

in making such assessments standard practice has

been dismayingly slow. Knowledge of many indirect

effects of roads has existed for decades and guidelines for considering these effects in assessments

have been available for more than ten years, but

agency protocols for explicitly addressing indirect

effects in impact assessments remain largely undeveloped and these effects rarely influence project

decisions (FHA 1992). Also, the CEQ has not yet

promulgated legally binding guidance to protect

against cumulative effects or the loss of biodiversity

26

1. Role of road-crossings in impairing movement/dispersal by individuals.

2. Role of roads in facilitating spread of non-native individuals via human vectors.

3. Relative importance of the three road-development phases in influencing

population dynamics.

4. Contribution of roads to local extinction and regional imperilment of

populations.

5. Type, magnitude, and direction of shifts in functional composition (e.g.,

trophic or reproductive traits) of communities in response to roads.

6. Influence of zoogeographical and regional contexts on impacts of roads.

7. Interactions (synergistic and antagonistic) between impacts of roads and

impacts of other anthropogenic activities.

8. Effectiveness of protective and restorative measures in preventing/reducing

impacts of roads.

9. Timeframes for recovery of biota following mitigation of road impacts.

10. Biotic responses to road removal.

Table 1. Key topics

needing additional

scientific study relevant to

assessments of road

impacts on individuals,

populations, and

communities of aquatic

biota. fish habitat

feature

Fisheries | www.fisheries.org | vol 29 no 12
27

featurefish habitat

December 2004 | www.fisheries.org | Fisheries

associated with road development (CEQ 1993, FHA

2002). Thus, current assessment tools do not incorporate the best available science and are inadequate

to ensure informed decisions on highway planning

(TRB 2002), as illustrated by our analysis of the I-73

DEIS (Figure 3). Additional research on the environmental effects of roads and on protocols for assessing

those effects has some potential to improve the information value of conventional impact assessments.

However, we suspect that agencies' lack of commitment to environmental concerns rather than a lack of

scientific knowledge currently limits effectiveness of

assessments of road impacts. Agency commitment to

protecting aquatic biota reflects the mores of society

at large. Public agencies will provide real protection

to aquatic biota only when the public holds those

agencies accountable for the continual decline in biological integrity and in the many ecological services

that intact biota provide to society.

Conclusions 

Roads have major impacts on aquatic biota but

these impacts traditionally have been grossly underassessed. Ignoring long-term, large-scale

environmental impacts of roads, which are often

severe and foreseeable, clearly fails to fulfill the intent

of key federal legislation on environmental protection. The public has not held road-building agencies

accountable for meeting its mandate to fully assess

road impacts. Rectifying this problem requires fundamental changes in how road impacts are defined,

measured, and incorporated into policy decisions. In

particular, the spatial and temporal extent of assessments must be expanded to match the scales over

which the most serious biological impacts of road

development are manifest. 

Aquatic science should play a more prominent

role in assessing road impacts. Investment by transportation agencies in research on environmental

consequences of roads has been too small relative to

the extent and severity of impacts (TRB 2002). Many

effects of roads on aquatic biota are poorly studied,

especially over large spatial and temporal scales.

Agencies also need to do a better job of finding, disseminating, and using the scientific knowledge that is

already available. Important sources of relevant scientific knowledge include scientists themselves,

scientific literature, and other agencies involved in

environmental issues. Although the impacts of a particular road on nearby areas are not precisely

predictable, we present a conceptual framework to

help managers organize the many common impacts of

roads on aquatic biota. 

The purpose of an environmental impact assessment is to describe the likely consequences of a

human action so that society can make an informed

decision about its desirability (i.e., cost versus benefit). Lack of attention to long-term, large-scale

impacts (i.e., major costs), as is common in assessments of roads, precludes fair assessments of desirability. Thus, decisions are biased in favor of more

road building, which contributes to the continued,

unsustainable urbanization of landscapes. Because

remediation of most road impacts is infeasible, efforts

to protect aquatic ecosystems are best applied to

changing the decision-making processes that precede

road building rather than to fixing the damage

caused by roads while and after they are built.

Indirect and cumulative effects of a road on environmental quality should be considered explicitly in the

planning stages, especially if the road's purpose

includes spurring economic development (FHA

1992). More complete assessments of the real environmental costs of roads would likely result in less

road building and slower rates of urban sprawl. Our

conceptual framework is designed to facilitate development of complete assessments of the biological

impacts of roads. 

Given the tremendous social, economic, and

environmental costs of new roads, especially highways, we believe that more thorough approaches to

assessing biotic impacts are long overdue. The proliferation of roads (and their attendant impacts) now

occurring in the United States is not an inevitable

condition of modern society, but a policy outcome.

Road policy can be changed. Agency ideology, not

scientific knowledge, is the main factor limiting the

completeness of environmental assessments.

Although scientists should continue to generate new

knowledge and tools relevant to assessing road

impacts, the main breakthrough needed is in societal

commitment to protecting intact biota and fully

functional ecosystems. It remains up to the agencies

and the publics they serve to muster the political will

to reinvent road policy. 

Acknowledgments

A.P. Wheeler's review of the literature on aquatic impacts of roads was supported by Virginians for Appropriate Roads. We thank William Hester, Than

Hitt, Kim Mattson, and three anonymous reviewers for helpful comments on

early drafts of the manuscript.
References

Angermeier, P. L., and J. R. Karr. 1994. Biological integrity versus

biological diversity as policy directives: protecting biotic resources.

BioScience 44:690-697.

Atkinson, R. B., and J. Cairns, Jr. 1992. Ecological risk of highways.

Pages 237-262 in J. Cairns, Jr., B. R. Niederlehner, and D. R. Orvos,

eds. Predicting ecosystem risk. Princeton Scientific, Princeton, NJ.

Booth, D. B. 1990. Stream-channel incision following drainage-basin

urbanization. Water Resources Bulletin 26:407-417.

Booth, D. B., and C. R. Jackson. 1997. Urbanization of aquatic

systems: degradation thresholds, stormwater detention, and the

limits of mitigation. Journal of the American Water Resources

Association 33:1077-1090.

Cline, L. D., R. A. Short, and J. V. Ward. 1982. The influence of

highway construction on the macroinvertebrates and epilithic algae

of a high mountain stream. Hydrobiologia 96:149-159.

CEQ (Council on Environmental Quality). 1993. Incorporating

biodiversity considerations into environmental impact analysis

under the National Environmental Policy Act. Available at

http://tis.eh.doe.gov/nepa/tools/guidance/Guidance-PDFs/iii-9.pdf 

Czech, B., P. R. Krausman, and P. K. Devers. 2000. Economic

associations among causes of species endangerment in the United

States. BioScience 50: 593-601.

Fausch, K. D., C. E. Torgersen, C. V. Baxter, and H. W. Li. 2002.

Landscapes to riverscapes: bridging the gap between research and

conservation of stream fishes. BioScience 52: 483-498.

FHA (Federal Highway Administration). 1992. Position paper:

secondary and cumulative impact assessment in the highway project

development process. Office of NEPA Facilitation, Washington, DC.

Available at www.fhwa.dot.gov/environment/nepa/2_C_imp.htm.

_____. 2002. Secondary and cumulative effects. Office of NEPA

Facilitation, Washington, DC. Available at

www.fhwa.dot.gov/environment/nepa/2nd_cml.htm.

Forman, R. T. T. 2000. Estimate of the area affected ecologically by the

road system in the United States. Conservation Biology 14:31-35.

Forman, R. T. T., and L. E. Alexander. 1998. Roads and their major

ecological effects. Annual Review of Ecology and Systematics

29:207-231.

Forman, R. T. T., and R. D. Deblinger. 2000. The ecological roadeffect zone of a Massachusetts (U.S.A.) suburban highway.

Conservation Biology 14:36-46.

Henshaw, P. C., and D. B. Booth. 2000. Natural restabilization of

stream channels in urban watersheds. Journal of the American Water

Resources Association 36:1219-1236.

Holling, C. S., and C. R. Allen. 2002. Adaptive inference for

distinguishing credible from incredible patterns in nature.

Ecosystems 5:319-328.

Jones, J. A., F. J. Swanson, B. C. Wemple, and K. U. Snyder. 2000.

Effects of roads on hydrology, geomorphology, and disturbance

patches in stream networks. Conservation Biology 14: 76-85.

Karr, J. R., and E. W. Chu. 1998. Restoring life in running waters,

better biological monitoring. Island Press, Washington, DC.

Kemp, S. J., and J. R. Spotila. 1997. Effects of urbanization on brown

trout Salmo trutta, other fishes and macroinvertebrates in Valley

Creek, Valley Forge, Pennsylvania. American Midland Naturalist

138:55-68.

Ketcheson, G. L., and W. F. Megahan. 1996. Sediment production and

downslope sediment transport from forest roads in granitic

watersheds. Research Paper INT-486. USDA Forest Service,

Intermountain Research Station, Ogden, UT.

Koryak, M. L. J. Stafford, R. J. Reilly, and P. M. Magnuson. 2001.

Highway deicing salt runoff events and major ion concentrations

along a small urban stream. Journal of Freshwater Ecology 16:125-

134.

Limburg, K. E., and R. E. Schmidt. 1990. Patterns of fish spawning in

Hudson River tributaries: response to an urban gradient? Ecology

71:1238-1245.

May, C. W., R. R. Horner, J. R. Karr, B. W. Mar, and E. B. Welch.

1997. Effects of urbanization on small streams in the Puget Sound

lowland ecoregion. Watershed Protection Techniques 2:483-494.

Morley, S. A., and J. R. Karr. 2002. Assessing and restoring the health

of urban streams in the Puget Sound basin. Conservation Biology 16:

1498-1509.

NRC (National Research Council). 1997. Toward a sustainable future:

addressing the long-term effects of motor vehicle transportation on

climate and ecology. National Academy Press, Washington, D.C.

Oberts, G. L. 1986. Pollutants associated with sand and salt applied to

roads in Minnesota. Water Resources Bulletin 22:479-483.

Osborne, L. L., and M. J. Wiley. 1988. Empirical relationships between

land use/cover and stream water quality in an agricultural watershed.

Journal of Environmental Management 26:9-27.

Paul, M. J., and J. L. Meyer. 2001. Streams in the urban landscape.

Annual Review of Ecology and Systematics 32:333-365.

Schlosser, I. J., and P. L. Angermeier. 1995. Spatial variation in

demographic processes of lotic fishes: conceptual models, empirical

evidence, and implications for conservation. American Fisheries

Society Symposium 17:392-401.

Southerland, M. T. 1995. Conserving biodiversity in highway

development projects. The Environmental Professional 17: 226-242.

_____. 2004. Environmental impacts of dispersed development from

federal infrastructure projects. Environmental Monitoring and

Assessment 94: 163-178.

Spellerberg, I. F. 2002. Ecological effects of roads. Science Publisher,

Inc. Enfield and Plymouth.

Stemberger, R. S., and C. Y. Chen. 1998. Fish tissue metals and

zooplankton assemblages of northeastern U.S. lakes. Canadian

Journal of Fisheries and Aquatic Sciences 55:339-352.

TRB (Transportation Research Board of the National Research

Council). 1995. Expanding metropolitan highways: implications for

air quality and energy use. Special Report 245. National Academies

Press, Washington, DC. 

_____. 2002. Surface transportation environmental research: a longterm strategy—Special Report 268. National Academies Press,

Washington, DC. 

Trombulak, S. C., and C. A. Frissell. 2000. Review of ecological effects

of roads on terrestrial and aquatic communities. Conservation

Biology 14:18-30.

USEPA (U.S. Environmental Protection Agency). 1996. Indicators of

the environmental impacts of transportation. EPA 230-R-96-009,

Washington, DC.

_____. 2000. The quality of our nation's waters. EPA 841-S-00-001,

Washington, DC.

Van Bohemen, H. D., and W. H. Janssen van de Laak. 2003. The

influence of road infrastructure and traffic on soil, water, and air

quality. Environmental Management 31:50-68.

28 Fisheries | www.fisheries.org | vol 29 no 12
Van Hassel, J. H., J. J. Ney, and D. L. Garling. 1980.

Heavy metals in a stream ecosystem at sites near

highways. Transactions of the American Fisheries

Society 109:636-643.

VDOT (Virginia Department of Transportation). 2000.

I-73 Location study between Roanoke and the North

Carolina state line: draft environmental impact

statement & section 4(f) evaluation. Richmond, VA.

_____. 2003. Press release. EPA calls VDOT "model of

environmental leadership." VDOT, Richmond, VA.

Available at www.virginiadot.org/infoservice/news/

CO05292002-EPA.asp.

Wang, L., J. Lyons, P. Kanehl, and R. Bannerman.

2001. Impacts of urbanization on stream habitat and

fish across multiple spatial scales. Environmental

Management 28:255-266.

Wang, L., J. Lyons, P. Kanehl, R. Bannerman, and E.

Emmons. 2000. Watershed urbanization and changes

in fish communities in southeastern Wisconsin

streams. Journal of the American Water Resources

Association 36:1173-1189.

Warren, M. L., Jr., and M. G. Pardew. 1998. Road

crossings as barriers to small-stream fish movement.

Transactions of the American Fisheries Society 127:

637-644.

Waters, T. F. 1995. Sediment in streams: sources,

biological effects, and control. American Fisheries

Society Monograph 7, Bethesda, MD.

Wear, D. N., and P. Bolstad. 1998. Land use changes in

southern Appalachian landscapes: spatial analysis and

forecast evaluation. Ecosystems 1:575-594.

Weaver, L. A., and G. C. Garman. 1994. Urbanization

of a watershed and historical changes in a stream fish

assemblage. Transactions of the American Fisheries

Society 123:162-172.

Wellman, J. C., D. L. Combs, and S. B. Cook. 2000.

Long-term impacts of bridge and culvert construction

or replacement on fish communities and sediment

characteristics of streams. Journal of Freshwater

Ecology 15:317-328.

Wheeler, A. P., A. E. K. Rosenberger, and P. L.

Angermeier. 2003. Potential impacts of I-73 on

stream habitat and biota, with emphasis on the

endangered Roanoke logperch. Final report to

Virginians for Appropriate Roads, Rocky Mount, VA. 

Whitney, A. N., and J. E. Bailey. 1959. Detrimental

effects of highway construction on a Montana stream.

Transactions of the American Fisheries Society 88:72-

73.

Wilbur Smith Associates. 1998. Appalachian

Development Highways economic impact studies.

Final report to Appalachian Regional Commission,

Washington, DC.

Wolman, M. G., and A. P. Schick. 1967. Effects of

construction on fluvial sediment, urban and suburban

areas of Maryland. Water Resources Research 3:451-

464.

Wood, P. J., and P. D. Armitage. 1997. Biological effects

of fine sediment in the lotic environment.

Environmental Management 21:203-217.

29

featurefish habitat

December 2004 | www.fisheries.org | Fisheries