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Journal of Applied
Ecology
2005
42
, 208–217
© 2005 British
Ecological Society
Blackwell Publishing, Ltd.Oxford, UKJPEJournal of Applied Ecology0021-8901British Ecological Society, 20054 2005422
Original ArticleEcological success in river restorationM. A. Palmer et al.
FORUM
Standards for ecologically successful river restoration
M.A. PALMER,* E.S. BERNHARDT,* J. D. ALLAN,† P.S. LAKE,‡
G. ALEXANDER,† S. BROOKS,‡ J. CARR,§ S. CLAYTON,¶ C. N. DAHM,**
J. FOLLSTAD SHAH,** D. L. GALAT,†† S. G. LOSS,‡‡ P. GOODWIN,¶
D.D. HART,§ B. HASSETT,* R. JENKINSON,§§ G.M. KONDOLF,¶¶
R. LAVE,¶¶ J.L. MEYER,*** T.K. O’DONNELL,†† L. PAGANO¶¶ and
E. SUDDUTH***
*
Department of Entomology, University of Maryland, USA and Department of Biology, Duke University, USA;
†
School of Natural Resources, University of Michigan, USA;
‡
Department of Biological Sciences, Monash
University, Australia;
§
Patrick Center for Environmental Research, Academy of Natural Sciences, USA;
¶
Ecohydraulics Research Group, University of Idaho, USA;
**
Department of Biology, University of New Mexico,
USA;
††
US Geological Survey, Cooperative Research Units, Department of Fisheries & Wildlife Sciences, University
of Missouri, USA;
‡‡
Grand Canyon Monitoring and Research Center, USA;
§§
Department of Fish and Wildlife
Resources, University of Idaho, USA;
¶¶
Department of Landscape Architecture and Environmental Planning,
University California, USA; and
***
Institute of Ecology, University of Georgia, USA
Summary
1.
Increasingly, river managers are turning from hard engineering solutions to ecologi-
cally based restoration activities in order to improve degraded waterways. River resto-
ration projects aim to maintain or increase ecosystem goods and services while
protecting downstream and coastal ecosystems. There is growing interest in applying
river restoration techniques to solve environmental problems, yet little agreement exists
on what constitutes a successful river restoration effort.
2.
We propose five criteria for measuring success, with emphasis on an ecological
perspective. First, the design of an ecological river restoration project should be based
on a specified guiding image of a more dynamic, healthy river that could exist at the
site. Secondly, the river’s ecological condition must be measurably improved. Thirdly,
the river system must be more self-sustaining and resilient to external perturbations so
that only minimal follow-up maintenance is needed. Fourthly, during the construction
phase, no lasting harm should be inflicted on the ecosystem. Fifthly, both pre- and post-
assessment must be completed and data made publicly available.
3.
Determining if these five criteria have been met for a particular project requires
development of an assessment protocol. We suggest standards of evaluation for each of
the five criteria and provide examples of suitable indicators.
4.
Synthesis and applications
. Billions of dollars are currently spent restoring streams
and rivers, yet to date there are no agreed upon standards for what constitutes ecolog-
ically beneficial stream and river restoration. We propose five criteria that must be
met for a river restoration project to be considered ecologically successful. It is critical
that the broad restoration community, including funding agencies, practitioners and
citizen restoration groups, adopt criteria for defining and assessing ecological success
in restoration. Standards are needed because progress in the science and practice of river
restoration has been hampered by the lack of agreed upon criteria for judging ecological
success. Without well-accepted criteria that are ultimately supported by funding and
implementing agencies, there is little incentive for practitioners to assess and report
restoration outcomes. Improving methods and weighing the ecological benefits of
various restoration approaches require organized national-level reporting systems.
Correspondence: Margaret Palmer, Department of Entomology, University of Maryland, College Park, MD 20742– 4454, USA
(fax +301 314 9290; e-mail mpalmer@umd.edu).
209
Ecological success
in river restoration
© 2005 British
Ecological Society,
Journal of Applied
Ecology
,
42
,
208–217
Key-words
:ecosystem rehabilitation, floodplain, monitoring, restoration assessment,
stream
Journal of Applied Ecology
(2005)
42
, 208–217
doi: 10.1111/j.1365-2664.2005.01004.x
Introduction
Healthy, self-sustaining river systems provide important
ecological and social goods and services upon which
human life depends (Postel & Richter 2003). Concern
over sustaining these services has stimulated major
restoration efforts. Indeed, river and stream restoration
has become a world-wide phenomenon as well as a
booming enterprise (NRC 1996; Holmes 1998; Henry,
Amoros & Roset 2002; Ormerod 2003). Billions of
dollars are being spent on stream and river restoration
in the USA alone (Palmer
et al
. 2003; Malakoff 2004).
Although there is growing consensus about the impor-
tance of river restoration, agreement on what constitutes
a successful restoration project continues to be lacking.
Given the rapid rate of global degradation of freshwaters
(Gleick 2003), it is time to agree on what constitutes
successful river and stream restoration.
We propose five criteria for measuring success, here-
after referred to as the standards for ecologically suc-
cessful river restoration. We chose a forum to propose
these in order to elicit broad input from the community,
including critiques and suggestions for expanding or
revising what we propose. It is our hope that, after debate
and careful consideration, the international scientific
community can reach consensus on a set of standards.
The next step would involve seeking approval of the
standards by the practitioner community and a diverse
array of scientific societies (e.g. ecological, water, and
restoration societies of various countries) and receiv-
ing eventual endorsement from the United Nations
Environmental Programme. The Comment papers by
Gillilan
et al
. (2005) and Jansson
et al
. (2005) in this
issue are encouraging and provide the kind of feedback
needed to advance the debate. Much thought has been
put into evaluating restoration and there is already
a rich literature (NRC 1992; Kondolf & Micheli 1995;
Kauffman
et al
. 1997). Drawing on this valuable body
of work and our recent experiences in establishing com-
prehensive river restoration databases for the USA and
Australia (Palmer
et al
. 2003; www.nrrss.umd.edu), we
identify elements that we consider essential to achiev-
ing ecological success. Once a general agreement on
reasonable success criteria has been reached, indicators
to evaluate ecologically successful restoration must be
identified.
Why the need for ecological standards?
The success of a restoration project could be evaluated
in many different ways. Was the project accomplished
cost-effectively? Were the stakeholders satisfied with
the outcome? Was the final product aesthetically pleas-
ing? Did the project protect important infrastructure
near the river? Did the project result in increased
recreational opportunities and community education
about rivers? Did the project advance the state of res-
toration science? However, for the following reasons,
we argue that projects initiated in whole or in part to
restore a river or stream must also be judged on whether
the restoration is an ecological success.
First, many projects are funded and implemented
in the name of restoration, with the implication that
improving environmental conditions is the primary aim.
Protecting infrastructure and creating parks are import-
ant activities but do not constitute ecological restoration
and many in fact actually degrade nearby waterways.
For example, riverfront revitalization projects may be
successful in increasing economic and social activity
near a river but can constrain natural processes of
the river and floodplain (Johansson & Nilsson 2002).
Similarly, channel reconfiguration from a braided to a
single-thread morphology may be aesthetically pleas-
ing but inappropriate for local geomorphic conditions
(Kondolf, Smeltzer & Railsback 2001). Thus, projects
labelled restoration successes should not be assumed to
be ecological successes. While other objectives have value
in their own right, river restoration connotes ‘ecological’
and should be distinguished from other types of improve-
ment. In the ideal situation, projects that satisfy stake-
holder needs and advance the science and practice of
river restoration (learning success) could also be
ecological successes (Fig. 1).
Fig. 1. The most effective river restoration projects lie at the
intersection of the three primary axes of success. This study
focuses on the five attributes of ecological success, but recognizes
that overall restoration success has these additional axes.
Stakeholder success reflects human satisfaction with restoration
outcome, whereas learning success reflects advances in scientific
knowledge and management practices that will benefit future
restoration action.
210
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et al.
© 2005 British
Ecological Society,
Journal of Applied
Ecology
,
42
,
208–217
Secondly, progress in the science and practice of river
restoration has been hampered by the lack of agreed
upon criteria for judging ecological success. Without
well-accepted criteria that are ultimately supported
by funding and implementing agencies, there is little
incentive for practitioners to assess and report restora-
tion outcomes. At present, information on most restora-
tion efforts is largely inaccessible and, despite pleas to
report long-term responses (Zedler 2000; Hansen 2001),
most projects are never monitored post-restoration
(NRC 1992). Our interest here is not which monitoring
methods are employed, but rather which criteria are used
to determine if a project is a success or failure ecol-
ogically. Bradshaw (1993), Hobbs & Norton (1996), Hobbs
& Harris (2001), Lake (2001) and many others have
long argued that restoration evaluation is crucial to the
future of ecological restoration. This begs the question
of evaluation with respect to what? What criteria can
be brought to bear in evaluating success? While the
objectives of ecosystem restoration are ultimately a
social decision; if they are to include ecological
improvement then we argue that the following criteria
must be met.
Five criteria for ecological success
:
Here we build upon the leitbild concept used to guide
channel restoration efforts in Germany (Kern 1992,
1994). We propose that the first step in river restoration
should be articulation of a guiding image that describes
the dynamic, ecologically healthy river that could exist
at a given site. This image may be influenced by irrevo-
cable changes to catchment hydrology and geomorpho-
logy, by permanent infrastructure on the floodplain and
banks, or by introduced non-native species that cannot
be removed. Rather than attempt to recreate unachiev-
able or even unknown historical conditions, we argue
for a more pragmatic approach in which the restoration
goal should be to move the river towards the least
degraded and most ecologically dynamic state possible,
given the regional context (Middleton 1999; Choi 2004;
Palmer
et al
. 2004; Suding, Gross & Housman 2004).
Throughout, we use the term ecological in a very
general sense to include biological, hydrological and
geomorphic aspects of natural systems. Thus an eco-
logically dynamic state is one in which the biota vary in
abundance and composition over time and space, as
they do in appropriate reference systems, and the chan-
nel shape and configuration also change in response to
the natural flow variability characteristic of the region.
An ecologically dynamic state is also resilient to exter-
nal perturbations. It is essential for practitioners to
recognize that there can be no universally applicable
restoration endpoint given the regional differences in
geology, climate, vegetation, land-use history and species
distribution.
Many approaches exist for establishing a guiding
image for restoration efforts; these approaches are not
mutually exclusive and are often complementary. First,
historical information, such as aerial photographs,
maps, ground photography and land and biological
survey records can be used to establish prior conditions
(Koebel 1995; Kondolf & Larson 1995; Toth
et al.
1995).
This can provide valuable insights into how the channel
or biota may have changed. For example, application
of US Government land office surveys from the early
1800s to describe floodplain forest vegetation in the
pre- or early settlement lower Missouri (Bragg &
Tatschl 1977) and upper Mississippi (Yin & Nelson 1996)
rivers provided a reference against which to design and
evaluate contemporary rehabilitation efforts (Galat
et al
.
1998; Sparks, Nelson & Yin 1998). Historical research
does not imply an objective of recreating historical
conditions, rather an attempt to account explicitly for
historical changes because of natural and anthro-
pogenic disturbances and to understand resource condi-
tions that may have been lost and irreversible changes
that may have occurred (Pedroli
et al
. 2002).
Secondly, relatively undisturbed or already re-
covered reference sites can be used to help frame restora-
tion goals (Rheinhardt
et al
. 1999), particularly where
historical information is lacking. These are, in effect,
space-for-time substitutions, with the reference sites
assumed to represent less disturbed channel conditions
and biological assemblage composition. In selecting
analogue sites, inherent differences among locations
in geology, climate, position in the catchment, fluvial
geomorphology, hydrology and zoogeography must be
considered. For example, if all reference sites are in
steeper upstream reaches because all the lowland reaches
have been affected by land-use change, their value to
guide restoration of the lowland channels will be lim-
ited. Similarly, understanding the historical context of
fish species distribution is necessary to understand
which species might reasonably be expected in a given
drainage basin (Strange 1999). Finding reference sites
for large rivers is particularly problematic. In some
cases, it may make sense to use a heavily impaired river
as a reference condition to ‘move away from’.
Thirdly, an analytical or process-based approach that
employs empirical models can be used to guide the design
of a project. For example, sediment transport functions
and empirical knowledge of relationships among chan-
nel, sediment and hydraulic variables can be used to
guide channel design, determine relationships between
sediments and discharge, and generally to assess whether
specific restoration actions are appropriate to a site
(Skidmore
et al
. 2001). Empirical relationships between
habitat and composition or recovery trajectories of biota
may guide the selection and placement of different types
of in-stream structures (Geist & Dauble 1998). Such
methods may be particularly useful when reference con-
ditions are lacking or channel equilibrium is in question.
211
Ecological success
in river restoration
© 2005 British
Ecological Society,
Journal of Applied
Ecology
,
42
,
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Fourthly, stream classification systems have been used
as a basis for developing guiding images for restoration
in North America and Europe. Classification (the
ordering of objects into labelled groups based on com-
mon characteristics) has been broadly applied to river
channels (Rosgen 1994; Poole, Frissell & Ralph 1997),
with more than 40 geomorphically based classification
schemes employed or proposed in various parts of the
world, based on factors such as channel pattern, gra-
dient, bed material size and sediment load (Kondolf
et al
. 2003). Experience to date suggests that classifica-
tion systems work best as guides to restoration when
they are developed for specific regions, like those used
to develop the leitbild or guiding image for restoration
of German rivers (Kondolf
et al
. 2003). Attempts to
develop restoration designs based on application of a
single classification system across many environments
have led to many failures in North America (Kondolf,
Smeltzer & Railsback 2001) because the specific pro-
cesses and history of the river under study were not
adequately understood.
Finally, common sense may be adequate in many
situations, where the guiding image is self-evident and
requires little or no expert analysis. All restoration
projects need not be preceded by complex and expensive
design. For example, areas with no riparian vegetation
may simply need to be replanted and streams in farm-
ing communities may only need livestock to be fenced
out to initiate ecological recovery.
:
Ecologically successful restoration will induce measur-
able changes in physicochemical and biological com-
ponents of the target river or stream that move towards
the agreed upon guiding image. Re-establishment of an
extirpated fish population, improved water clarity and
quality, and establishment of a seasonally inundated
meadow following dam removal are readily identified
signs of ecological recovery. Such endpoints may take
time, and the components being measured will usually
have trajectories of different shapes and rates because
they differ in their responses to the intervention (Fuchs &
Statzner 1990; Molles
et al
. 1998; Muotka & Laasonen
2002). An increase in variability may be a signal of suc-
cessful restoration because natural systems are inher-
ently variable. However, demonstrating improvement
may require evaluation of the variability of the restored
river’s components with respect to pre-restoration con-
ditions, an undisturbed or less degraded river, or from a
process-based understanding of the component dynamics.
How far the restoration project will move a system
towards the guiding image will depend on many factors,
some of which are non-ecological (e.g. existing infra-
structure limitations, stakeholder needs and values,
available funding). Additionally, constraints often exist
at the catchment scale, including constant factors such
as flow barriers (press disturbances) and spasmodic
events (pulse disturbances) such as sediment inputs
(Bond & Lake 2003). A clear understanding of scale and
severity of constraints is needed in order to prioritize
restoration activities and arrive at a co-ordinated scheme
of activity for the entire catchment (Bohn & Kershner
2002; Roni
et al
. 2002). In some cases, the large-scale
constraints are so severe that one must question whether
restoration of single reaches is an appropriate use of
valuable resources. However, with sufficient watershed
planning, the cumulative effects of multiple projects
may yield great ecological benefits. Individual projects
that are part of a large restoration scheme should be
evaluated within the larger context, particularly to
determine the effects on other regional projects.
Recognizing the many constraints, we argue that
projects are ecological successes when the river is moved
measurably towards the guiding image given the eco-
logical and non-ecological contexts. One of the most
difficult questions restorationists face is how much
restoration-related improvement is enough. The answer
lies at the intersection, where defined ecological and
stakeholder outcomes are met (Fig. 1) and future efforts
benefit from the understanding gained. Restoration
success should not be viewed as an all or nothing single
endpoint, but rather as an adaptive process where iter-
ative accomplishments along a predefined trajectory
provide mileposts towards reaching broader ecological
and societal objectives.
:
-
Ecosystems are subject to changing conditions because
of temporal variations in both natural factors and human
activities. Ecologically successful river restoration
creates hydrological, geomorphological and ecological
conditions that allow the restored river to be a resilient
self-sustainable system, one that has the capacity for
recovery from rapid change and stress (Holling 1973;
Walker
et al
. 2002). Natural river ecosystems are
both self-sustaining and dynamic, with large variability
resulting from natural disturbances. For example, scour-
ing floods can enhance biodiversity by reducing the
abundance of competitively dominant species that are
favoured by stable flows. There will also be temporal
variation in ecological characteristics (e.g. channel
alignment, levels of productivity) (Palmer, Ambrose &
Poff 1997; White & Walker 1997), although this vari-
ability does have limits (Suding, Gross & Housman 2004)
and for some rivers it can be predictable. Degraded
running water systems (e.g. following dam construction)
are typically characterized by a major reduction or
alteration in variability (Baron
et al
. 2002; Pedroli
et al
.
2002). Often the limits have been so far exceeded that
resilience has been lost (Suding, Gross & Housman 2004).
Unless some level of resilience is restored, projects
are likely to require on-going management and repair,
212
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et al.
© 2005 British
Ecological Society,
Journal of Applied
Ecology
,
42
,
208–217
the very antithesis of self-sustainability. Thus, we argue
that, to be ecologically successful, projects must in-
volve restoration of natural river processes (e.g. channel
movement, river–floodplain exchanges, organic matter
retention, biotic dispersal). Restoring resilience using
hard-engineering methods should not be the first
method of choice as they often constrain the channel.
However, there are situations in which engineered
structures may enhance resilience (e.g. grade restoration
facilities that prevent further incision and promote
lateral channel movement, Baird 2001; projects pro-
viding fish access to spawning reaches through culvert
redesign or by establishing pathways to the floodplain,
NRC 1992).
:
In the last century, Aldo Leopold (1948) stated that the
first ‘rule’ of restoration should be to do no harm.
Restoration is an intervention that causes impacts to the
system, which may be extreme (e.g. channel reconfigu-
rations). Even in such situations, an ecologically suc-
cessful restoration minimizes the long-term impacts to
the river. For example, a channel modification project
should minimize loss of native vegetation during in-
river reconstruction activity, and should avoid the fish
spawning season for construction work. Indeed, removal
of any native riparian vegetation should be avoided
unless absolutely necessary. Additionally, restoration
should be planned so that it does not degrade other
restoration activities being carried out in the vicinity (e.g.
by leading to permanent increases in the downstream
transport of sediments that are outside the historical
range of sediment flux).
:
- -
Ecological success in a restoration project cannot be
declared in the absence of clear project objectives from
the start and subsequent evaluation of their achieve-
ment (Dahm
et al
. 1995). Both positive and negative
outcomes of projects must be shared regionally, nation-
ally and internationally (Nienhuis & Gulati 2002). As
we gain experience with ecological restoration and
document our findings, and should restoration methods
prove effective across a range of conditions, it may be
logical to reduce the effort invested in assessment.
Determination of when and where restoration
monitoring can be reduced is a future challenge. Some
projects, such as riparian planting of native trees for
bank stabilization, are sufficiently straightforward that
the assessment can be periodic visual or photographic
checks to ensure that the plants are alive and success-
fully stabilizing the bank. Other projects, such as in-stream
habitat improvement, may be sufficiently common in
some regions that only a sample of projects need thor-
ough monitoring and evaluation. A project-by-project
determination of the appropriate level and complexity
of analysis should be made based on the size of the
project and the scale of its likely impacts and benefits
(Holl, Crone & Schultz 2003; Anand & Desrochers
2004). In general, the learning potential of a project
will depend upon the investment in baseline data, study
design and post-project monitoring, but even projects
lacking baseline data and post-project monitoring can
yield useful insights (Downs
et al
. 2002). Funders and /
or regulators of restoration projects should ensure that
an appropriate number of projects include broad eco-
logical monitoring and evaluation. A critical first step
is for regulatory and funding entities that promote, per-
mit and fund river restoration to create and maintain
databases that use a standardized protocol to record
where and how restoration is performed. These data-
bases should also maintain and analyse the monitoring
information associated with restoration projects.
Assessment is a critical component of all restoration
projects but achieving stated goals is not a prerequisite
to a valuable project. Indeed, well-documented projects
that fall short of initial objectives may contribute more
to the future health of our waterways than projects that
fulfil predictions. As summarized by Petroski (1985),
‘No one wants to learn by mistakes, but we cannot
learn enough from successes to go beyond the state of
the art’. For example, while post-project monitoring of
small-scale fish habitat rehabilitation in lowland rivers
of the UK revealed little improvement in habitat con-
ditions, the work identified important issues of scale,
site location and water quality that will benefit future
restoration efforts (Pretty
et al
. 2003). While the level
of monitoring will vary, all restoration assessments
should be communicated beyond project proponents
and funders to other stakeholders, restoration practi-
tioners, scientists and policy makers.
Ecologically sound restoration: avoiding
ineffective approaches
Standards for ecologically successful restoration should
inform the design and implementation processes so
that the most effective course of action is chosen. Dif-
ferent restoration activities should be selected based on
the extent and type of damage, land-use attributes
of the catchment, the size and position of the river within
the catchment, and stakeholder needs and goals. Even
when constraints are significant, there are almost always
choices that are more or less ecologically sound, as
illustrated by the following four examples.
1
A major problem in urban streams is an increase in
peak flows because of runoff from impervious surfaces
in the watershed. An ecologically effective restoration
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in river restoration
© 2005 British
Ecological Society,
Journal of Applied
Ecology
,
42
,
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approach may be to create floodplain wetlands to
intercept surface runoff and pollutants and to increase
infiltration. An ecologically ineffective restoration
approach might involve protecting infrastructure through
hard engineering such as rock walls and rip rap. The
first approach is more ecologically sound because it
improves river conditions by using the natural ability
of a healthy river system to cleanse pollutants and
moderate flow variability. In addition, this approach
requires minimal long-term maintenance and repair and
thus is more self-sustaining than many hard-engineered
approaches.
2
A legacy of timber harvest and log drives in forested
areas is a scarcity of wood within river channels and
mature trees along river banks. Ecologically effective
restoration should include a change in forest management
to allow riparian trees to mature as a future source of
in-channel wood. An ecologically ineffective activity is
placement of wood structures using machinery that
causes permanent damage to riparian vegetation, or is
intended to ‘lock’ the channel in place, thereby prevent-
ing the natural migration process important for future
recruitment of wood to the channel. The former is
more ecologically sound because it is based on natural
replenishment of wood and does not hinder natural
processes. Another example of restoration related to
timber harvesting is the increase in structural hetero-
geneity of streams using boulders which can lead to
enhanced ecosystem function (Lepori
et al
. 2005).
3
In large lowland rivers, grading, levee breaching or levee
widening can be an ecologically effective restoration
activity to reconnect the channel with its floodplain.
An ecologically ineffective restoration activity would
include periodic dredging. The first restores a natural,
periodic process that provides many human and eco-
logical benefits, including propagation of native species
and natural flood retention. The latter is likely to be
costly and less effective ecologically because it has sig-
nificant, short-term disruptive impacts and relies on
regular, costly maintenance.
4
Some relatively undisturbed river ecosystems are
impacted by upstream impoundments or water
withdrawals. In these systems, ecologically effective
restoration will move the system closer to the natural
hydrograph. Ecologically ineffective restoration will
focus exclusively on maintaining some minimum in-
stream flow, but will fail to re-establish the natural flow
regime. The first approach will be successful in that it
may restore cues for fish spawning and riparian plant
germination, high flows for nutrient regeneration and
channel maintenance, and groundwater connectivity.
The latter approach will maintain the river channel
but without re-establishing these additional ecosystem
benefits.
Implications of setting standards and moving
towards implementation
We have described five criteria for ecologically successful
restoration, with the goal of encouraging more projects
that convert damaged rivers into sustainable ecosystems.
This still leaves unanswered questions. Can we actually
implement these standards? What types of evaluations
are required to determine if a project has met each suc-
cess criterion? What indicators are meaningful, afford-
able and repeatable for project evaluations?
Such indicators will vary depending on the nature
of the ecological goals, which could range from re-
establishing a single species to restoring multispecies
communities or ecosystem processes. Additionally,
indicators could be selected from two perspectives, one
seeks to move away from a degraded state (e.g. show an
improvement in water quality relative to pre-restoration
conditions) while the other seeks to approach some
desired condition (e.g. demonstrate that water quality
is closer to values for reference sites). To make effective
use of indicators, there must be clear and realistic goals,
which will vary greatly depending on context and with
restoration procedures. For example, goals and indicators
for steep, headwater streams would differ greatly from
those for lowland, floodplain rivers.
Selection and use of ecological indicators is now a
major area of research, with some excellent lists of the
properties of good indicators already available (Davis
& Simon 1995; Jackson, Kurtz & Fisher 2000; Dale &
Beyeler 2001). In the context of river restoration, we
agree that indicators should be easily measured, be sen-
sitive to stresses on the system, demonstrate predictable
responses to stresses (i.e. restoration interventions) and,
ideally, be integrative. Thus we suggest guidelines for
evaluation of each of the five criteria as well as examples
of suitable indicators (Table 1).
Ideally, implementation of national and international
programmes to evaluate ecological success in restora-
tion would not only advance our understanding of how
best to restore streams and rivers, but would also influence
the expectations and goals of stakeholders. This issue is
also discussed by Jansson
et al
. (2005). However, stake-
holder success and/or learning success are possible
without ecological success, and are valid criteria for suc-
cess in their own right (Fig. 1). It is important to
emphasize, however, that different forms of success should
not be confused. Restoration projects should not be
labelled ecological restoration unless they meet the five
criteria we outline. For example, if river conditions do
not improve measurably or are not self-sustaining, but
project assessment leads to new ideas for improving the
ecological conditions via restoration, then the project could
be considered a learning success but not an ecological
214
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Ecological Society,
Journal of Applied
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,
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,
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Table 1. A provisional summary of guidelines that could be used to evaluate the five criteria for ecologically successful river
restoration. The list is not comprehensive. The effort, cost and complexity of the evaluation process should be commensurate with
ecological risk, project cost and societal concern. Simple and inexpensive methods should be employed whenever possible. The
indicators for each standard are illustrative of possible assessment tools for each criterion, the specific indicator selected for a
project will depend on the project focus (e.g. biological, water quality, geomorphic)
Criteria Evaluation guidelines References
1 Guiding image of
dynamic state
The guiding image should take into account not only
the average condition or some fixed value of key system
variables (hydrology, chemistry, geomorphology, physical
habitat and biology) but should also consider the range of
these variables and the likelihood they will not be static.
It should explicitly recognize human-induced changes to
the system, including changes in the range of key variables
Ideally, this plan should consider local as well as watershed-
scale stressors, and should consider how much local
restoration can contribute to watershed-level restoration.
Poff et al. (1997), Bohn &
Kershner (2002), Jungwirth,
Muhar & Schmutz (2002),
Gilman, Abell & Williams
(2004), Poole et al. (2004)
Indicators: presence of a design plan or description of
desired goals that are not orientated around a single, fixed
and invariable endpoint (e.g. static channel, temporally
invariant water quality).
2 Ecosystems are
improved
Appropriate indicators of ecological integrity or ecosystem
health should be selected based on relevant system
attributes and the types of stressors causing impaired
ecological conditions. The expected rate of improvement
will vary with the degree of impairment, the degree to which
restoration reduces key stressors, and the sensitivity of the
selected indicators to changes in stressor levels. Change may
be relative to a reference site or away from a degraded state
(see text).
Barbour et al. (1999), Karr
& Chu (1999), Middleton
(1999), Bjorkland, Pringle
& Newton (2001), Bailey,
Norris & Reynoldson (2004),
Lepori et al. (2005)
Indicators: water quality improved; natural flow regime
implemented; increase in population viability of target
species; percentage of native vs. non-native species
increased; extent of riparian vegetation increased; increased
rates of ecosystem functions; bioassessment index
improved; improvements in limiting factors for a given
species or life stage (e.g. decrease in percentage fines
in spawning beds or decrease in stream temperature).
3Resilience is increased System should require minimal on-going intervention
and have the capacity to recover from natural disturbances
such as floods and fires, and to recover from further human
encroachment.
Holling (1973), Loucks
(1985), Gunderson (2000),
Weick & Sutcliffe (2001)
Indicators: few interventions needed to maintain site;
scale of repair work required is small; documentation that
ecological indicators (see 2 above) stay within a range
consistent with reference conditions over time.
4 No lasting harm Pre- and post-project monitoring of selected ecosystem
indicators (see 2 above) should demonstrate that impacts
of the restoration intervention did not cause irreversible
damage to ecological properties of the system.
Underwood (1996), Biggs
et al. (1998), Sear, Briggs &
Brookes (1998), Steinberger
& Wohl (2003)
Indicators: little native vegetation removed or damaged
during implementation; vegetation that was removed has
been replaced and shows signs of viability (e.g. seedling
growth); little deposition of fine sediments because of
implementation process.
5 Ecological
assessment is
completed
Ecological goals for project should be clearly specified, with
evidence available that post-restoration information or data
were collected on the ecosystem variables of interest (see 2
above). The level of assessment may vary from simple
pre- and post-comparisons to rigorous statistically designed
analyses (e.g. using before–after, treatment–control or both
types of comparisons) but results should be analysed and
disseminated.
Kondolf (1995), Bash &
Ryan (2002), Downs &
Kondolf (2002), Downes
et al. (2002), Gilman,
Abell & Williams (2004)
Indicators: available documentation of preconditions
and post assessment.
215
Ecological success
in river restoration
© 2005 British
Ecological Society,
Journal of Applied
Ecology
,
42
,
208–217
success. Finally, we wish to emphasize that conservation
of rivers prior to their degradation should still be the
greater priority. Where conservation has failed and crucial
ecological services are diminished, restoration that is ‘eco-
logically’ sound should be the option of choice (Dobson,
Bradshaw & Baker 1997; Ormerod 2003).
Acknowledgements
We thank the following for their support of the
National River Restoration Science Synthesis project
(www.nrrss.umd.edu): the University of Maryland, the
State of Maryland’s Department of Natural Resources,
the Lucile and David Packard Foundation, the National
Center for Ecological Analysis and Synthesis (NSF),
the Charles S. Mott Foundation, CALFED, the
Altria Foundation, and the United States Geological
Survey’s National Biological Information Infrastructure
program.
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