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Ecological restoration:Our hope for the future?

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Abstract

Ecological restoration is widely employed from tens to millions of hectares in space, and from tens of days to thousands of years in time, which forces consideration of it thoroughly. We argue that three questions are the most important among the contents relevant of ecological restoration, including why, what and how to restore degraded systems. Why to restore determines whether or not the degraded ecological systems should be restored. What to restore is the goal of ecological restoration. The explicit goal of ecological restoration is necessary to guide ecological restoration workers in pursuit of excellence and prevent restoration from being swamped by purely technological activities. And how to restore means the methods and steps we should apply. To ensure the final success of ecological restoration, restored sites should be monitored and managed for long time to determine whether the selected methods are appropriate, and can be remedy better. Only to deal with these effectively, ecological restoration would be the hope for the future.
CHINESE GEOGRAPHICAL SCIENCE
Volume 14, Number 4, pp. 361-367, 2004
Science Press, Beijing, China
ECOLOGICAL RESTORATION:OUR HOPE FOR THE FUTURE?
WANG Xu-gao ks, LI Xiu-zhen l, HE Hong
S t,-', HU
Yuan-man ~
( 1. Institute ofA pplied EcohJgy, Chilwse .4 c~utemy ~fSciences, Shenyang 110016. P. R. China;
2. 5'<'ho,d o,/N~allrd Resources, I/tffversity <f Missouri-Columbi~l, Columbia, MO 65211, USA ;
3. Graduate School ~f Chim'se A c(ulemy (f Sciences, Beijing 100039, P. R. China)
ABSTRACT:
Ecological restoration is widely employed from tens to millions of hectares in space, and from tens of
days to thousands of years in time, which forces consideration of it thoroughly. We argue that three questions are the
most important among the contents relevant of ecological restoration, including why, what and how to restore de-
graded systems. Why to restore determines whether or not the degraded ecological systems should be restored. What
to restore is the goal of ecological restoration. The explicit goal of ecological restoration is necessary to guide eco-
logical restoration workers in pursuit of excellence and prevent restoration from being swamped by purely techno-
logical activities. And how to restore means the methods and steps we should apply. To ensure the final success of e-
cological restoration, restored sites should be monitored and managed for long time to detennine whether the selected
methods are appropriate, and can be remedy better. Only to deal with these effectively, ecological restoration would
be the hope for the future.
KEY WORDS:
ecological restoration: degraded systems; ecosystem monitoring
CLC number: X 171.4 Document code: A Article ID: 1002-0063(2004)04-0361-07
1
INTRODUCTION
All organisms modify their environment, and human
being is not exception. With the global population pro-
pelling towards seven billion, and the power of sci-
ence and technology expanding, the impact of human
beings on the natural environment occurs at a variety
of spatial and temporal scales. In the area human be-
ings live on, most natural ecosystems are converted in-
to agricultural or industrial land. The structure and
functiofi of original ecosystems have been destroyed,
and hardly any ecosystem on the Earth' surface was
free of pervasive human influence. Some ecosystems
have been damaged seriously, which resulted in a se-
ries of environmental problems, such as industrial pol-
lution, deforestation, desertification, soil erosion, loss
of biodiversity and shortage of freshwater. These in-
creasingly serious environmental problems have been
and are posing great threat to the living environment
of human beings and sustainable development of hu-
man society. Fortunately, people have been conscious
of the severely environmental problems, and begin to
deal with them. Under these situations, a new science,
Received date: 2004-04-29
restoration ecology, occurred in the 1980s. The emerg-
ing of restoration ecology provides a tool and opportu-
nity to solve ecological problems and realize sustain-
able development.
Restoration ecology is a new science on ecological
restoration, which includes biological remediation, and
engineering restoration. Research of ecological
restoration has been for approximately 100 years until
now. In 1935, LEOPOLD and his assistants restored a
pasture about 24ha in the arboretum of Wisconsin U-
niversity. Subsequently, he found that fire was impor-
tant in maintaining and managing the pasture (JOR-
DON
et d.,
1987). From 1950 to 1970, people in Eu-
rope, North America, and some other countries, no-
ticed the environmental problems, and adopted lots of
projects with biological or other measures to study and
deal with them, such as restoration of mine, soil ero-
sion, cleaning treatment of polluted water (CAIRNS,
1995; BRADSHAW, 1997). Although there were
some positive results, the study on mechanisms of eco-
logical restoration was few. After 1970, on the one
hand, practices to restore and rehabilitate ecological
resources degraded by overuse had become more and
Foundation item: Under the auspices of the National Natural Science Foundation of China (No.40331008, 30270225)
Biography: WANG Xu-gao (1980-), male, a native of Rizhao of Shandong Province, Ph. D. candidate, specialized in landscape
ecology, GIS and remote sensing. E-mail: wangxugao@hotmail.com
Correspondent: El Xiu-zhen([970-), professor, specialized in landscape structure and modeling. E-mail: lixz@iae.ae.cn
362
more popular all over the world, especially in devel-
oped countries. On the other hand, restoration ecolo-
gist began to communicate with each other, for exam-
ple, the International Symposium on the Recovery of
Damaged Ecosystems was held in America in 1975.
Scientists who discussed the theories and methods on
the recovery of damaged ecosystems were asked to
collect scientific data and information of damaged e-
cosystems, to study technology, and to establish the in-
ternational cooperation. In 1984, the symposium on
restoration ecology were held at Wisconsin, USA. In
the meantime, some books about ecological restoration
had been published in succession. For example, the
book The Recovery Process on Damaged Ecosystems
edited by CAIRNS (1980) was published. In the same
year, BRADSHAW and CHADWICK (1980) pub-
lished the book Restoration of Land, the Ecology
and Reclamation of Derelict and Degr(uted Land. In
1985, a series of monographs about ecological restora-
tion on forest, wetland, grassland, coast, were pub-
lished. The terminology of restoration ecology was
first put forward in that year. After the international
society of ecological restoration was founded in 1987,
especially the journal Restoration Ecology was initiat-
ed in 1993, restoration ecology got further develop-
ment. A lot of articles about ecological restoration
were published in some journals, such as Restoration
Ecology, Restoration and Management Notes, Journ-
al of Applied Ecology and so on. According to Journ-
al of Applied Ecology in the recent 40 years, submis-
sions on restoration ecology have increased and now
contribute at least 8%-12% of the papers published
annually. Examples from subjects such as conserva-
tion biology, pollution ecology, and ecological model-
ing showed that notions of restoration or recovery are
now implicit in the philosophy of applied ecology
(ORMEROD, 2003).
However, it was relatively late when attention was
been paid to ecological restoration in China. In the
1950s-1960s, only a few projects on forest restoration
were employed in order "to increase the productivity of
woods, and enhance the coverage rate of forest. After
1980, ecological degradation, environmental pollution
became severer and severer, which attracted the high
attention of some governmental departments. Accord-
ing to various degraded ecosystems, such as mined
lands, forest, island ecosystems, abandoned farmland
and grassland, a lot of restoration projects had been
widely applied (LI and ZHENG, 1995; PENG, 1996;
CUI and LIU, 1999; HAO, 2001; REN et d., 2001;
HOU et al., 2002; JIANG et al., 2002; XIA and CAI,
WANG Xu-g~u~, LI Xiu-zhen, HE Hong Set al.
2002). Due to these, some results and theories oc-
curred and enriched the discipline of restoration ecolo-
gy in China (ZHANG and XU, 1999; REN and PENG,
2002; XIANG et d., 2003).
The final definition of ecological restoration is not
clear until now, but ecological restoration becomes
more and more popular. Human beings have restored
variously degraded ecosystems in different regions, and
from different aspects, using diverse technologies,
which makes the scope and extent of ecological restora-
tion become larger and larger. However, not all human
beings agree with ecological restoration. KLOOR's ar-
ticle (2000) about the restoration of North America's
forests suggested that it might be time to retire the word
"restoration". He pointed out that there were at least
three problems with the field of restoration ecology.
First, the arbitrariness of determining which time period
in the past should be the target of restoration efforts.
Second, there is an implication of stasis with the word
"restored". Third, true restoration is simply impossi-
ble. The climate is no longer the same, and key spec-
ies are absent and new species are present, which make
it impossible to truly restore the habitat to any prior
state. HIGGS published an article about no justification
to retire the term "restoration" to disprove the three
points (HIGGS, 2000). He considered that a substantial
body of literature addresses the determination of refer-
ence conditions, and restoration ecologists have worked
hard to refine methods for defining appropriate refer-
ence points in time and space, that it is a common tenet
in the field that contemporary restoration is a dynamic
process of restoring not only composition and structure,
but also processes including disturbance regimes and e-
cosystem functions that lead to change over time, and
that ecological restoration promotes the flourishing of
indigenous species and communities, ecosystem fluxes,
and sustainable cultural practices. He also believed that
restoration ecology is the branch of applied ecology
that forms the scientific basis for such endeavors.
We argue that the debate about ecological restoration
is not ended now, and will exist for a long time in the
future, which will be not prevented, but promote the
advancement of both theories and practices in the eco-
logical restoration. This paper addresses three most
important questions of ecological restoration, that is,
the reasons (why to restore?), the scope and extent
(what to restore?), and the methods (how to restore?)
of ecological restoration. All three questions are pri-
mary, indispensable in the discipline of restoration e-
cology.
Ecological Restoration: Our Hope for the Future?
2 WHY TO RESTORE
In the three questions mentioned above, the first ques-
tion is the most important. Because only when we un-
derstand why to restore, we could address the following
questions. If we do not know why to restore, all the
work about ecological restoration would lose meaning.
Many people would think the answer to the question is
simple. As we discussed above, environmental prob-
lems, such as industrial pollution, deforestation, soil
erosion, loss of biodiversity and shortage of freshwater,
have become more and more serious, and have been
great threat to the living environment of human being
and sustainable development of the society. Now, we
need to decide whether we wish to proceed with this
huge transformation of our planet, and in doing so, put
our continued existence at increasing risk. Or whether
we want to seek alternatives in which we aim to protect
the resources, both living and biotic resources, which
we have left, and set about repairing some of the dam-
age we have inflicted in the past. It is our hope that we
have the collective wisdom to choose the latter course,
and it is in this context that we consider the rapidly de-
veloping field of restoration ecology (HOBBS and
HARRIS, 2001). However, because the degree of dam-
aged ecosystems differs greatly, we should decide
whether to "do nothing" (on the one hand, the system is
too degraded to warrant restoration, or, on the other
hand, biological integrity is relatively intact and there-
fore either none, or minimal, restoration is required) or
to "do something" (because restoration is worthwhile,
urgent and feasible) (SAMWAYS, 2000). So we should
know whether the damaged ecological systems fall in
the two extremes of "do nothing", or not. If one area
falls where we do nothing, it may be because the area is
so intact that urgent attention will make little difference.
On the other hand, we may do nothing because the area
is so degraded that to do something truly meaningful
would be a monumental task. Except the two extremes,
ecological restoration may be necessary and have some
meaning.
3 WHAT TO RESTORE
The original definition about ecological restoration
adopted by the Society for Ecological Restoration
(SER) in 1990 was the longest-lived and the most con-
troversial: "Ecological restoration" is the process of in-
tentionally altering a site to establish a defined, indige-
nous, historic ecosystem. The goal of this process is to
emulate the structure, function, diversity, and dynamics
363
of the specified ecosystem. This definition, and similar
ones proposed in its wake indicate a lack of agreement
on the most basic issues of what restoration is and what
restoration ecologists are attempting to accomplish
(HIGGS, 1997). In the recent definition by SER, eco-
logical restoration is the process of assisting the recov-
ery and management of ecological integrity. Ecological
integrity includes a critical range of variability in biodi-
versity, ecological processes and structures, regional
and historical context and sustainable cultural practices
(http://www.ser.org). This broad definition includes
many elements but does not address how to restore a
spoiled site or fragmented landscape. Of course, the
SER holds no monopoly on definitions. There were also
many definitions by restoration ecologists (BRAD-
SHAW and CHADWICK, 1980; ROGERS-MAR-
TINEZ, 1992; CAIRNS, 1995; HIGGS, 1997). Al-
though these definitions are not all-sided, they expand
the scope of ecological restoration. HIGGS (1997) ar-
gued that defining an end point for restoration was as
much an ethical matter as a technical one, but scientifi-
cally trained restoration ecologists had largely ignored
the former issue. He even argued that good restoration
requires an expanded view that included historical, so-
cial, cultural, political, aesthetic, and moral aspects. Be-
cause the wide context of restoration, there are so many
similar terms, such as rehabilitation, reclamation, re-
greening, and so on (SAMWAYS, 2000). Lack of preci-
sion in the definition of ecological restoration has been
a controversial issue for decades in restoration ecology
as a science, but has not prevented its effective applica-
tion. Whatever the definition of ecological restoration
is, we consider that the important part of the restored
system should be harmonious with nature and self-sus-
taining in the future, and other parts are additional.
Goal definition is more important than definition of
the term (ecological restoration), because the clear e-
nunciation of goals is essential for what to restore, and
the ability to assess the progress toward success. We
should define the goal in restoration projects, because it
sets expectations, drives the detailed plans for actions,
and determines the kind and extent of post-project mon-
itoring. Not surprisingly then, the nature of restoration
goals is the subject of frequent comment (EHREN-
FELD, 2000). The goals set for restoration projects are
highly variable, partly because restoration ecology has a
complex, heterogeneous lineage (HOBBS and NOR-
TON, 1996, DIGGELEN
et d.,
2001; HOBBS and
HARRIS, 2001 ). In the meantime, the goals for restora-
tion vary greatly, as the spatial and temporal scales cha-
nge. The spatial scales have many hierarchies, such as
364
population, community, ecosystem, and landscape. Dif-
ferent perspectives need to set different goals for
restoration. Species-centered goals for restoration are
reflected in a variety of recent publications, such as in-
vertebrates, fishes, and birds (FALK
et
o/., 1996; DON-
ALD
et al.,
2001; WOLFF
et cd.,
2001). The advantages
of species-centered restoration are clear: species threat-
ened by extinction are rescued, or at least given a better
chance of survival. Elsewhere, however, ecosystem
perspectives have remained prominent, for example
with respect to the restoration of grasslands, forests,
heathlands, peatlands, rivers, lakes and wetlands affect-
ed by overuse of people. The advantages of using e-
cosystem-level restoration are that ecosystem-level
framework encourages restoration ecologists to recog-
nize the large-scale processes' necessity for species'
persistence, to recognize the dynamic nature of ecologi-
cal entities, and to encourage the integration of manage-
ment goals of diverse agencies, interested groups
(EHRENFELD, 2000). Besides these population or e-
cosystem views, perhaps landscape scale restoration is
most challenging, and restoring entire landscape is be-
ing discussed recently (LAMB, 1998; RADELOFF
et
a/., 2000). Without large-scale support, small-scale
restoration may create unstable sites and landscapes
(WHISENANT, 1999).
On the other hand, temporal scales are also important
for ecological restoration. It is increasingly clear that
process rates of both biotic transformations and species
turnover are often low and should be expressed in
decades rather than in years (DIGGELEN
et ~d.,
2001).
According to this, the goals should be separated into 3
levels: recent goals (achieved in months), intermediatte
goals (achieved by years) and ultimate goals (achieved
by decades or even hundreds). The ultimate goal of
many ecological restoration projects is to return ecosys-
tems structures, functions, and processes to "nature" or
reference conditions, while the recent or intermediate
goals are the following phase to ultimate goals. People
often want to achieve the ultimate goal as quickly as
possible, and there is no time to address the problem in
a proper scientific way, which may lead to unwanted re-
sults.
In all, these goals defined by restoration ecologists are
all fine in general terms, but how do we turn them into
effective goals or even efficient goals for specific pro-
jects? HOBBS and HARRIS suggested that we needed
a clear rationale for setting goals, which took into ac-
count the nature of the systems being restored, the fac-
tors leading to degradation and the types of action re-
quired to achieve restoration of different attributes
WANG Xu-g~u~, LI Xiu-zhen, HE Hong Set ¢tl.
(HOBBS and HARRIS, 2001). We should adjust goals
to local conditions, for there are no common templates
for all restoration projects.
4 HOW TO RESTORE
Once the restoration goal has been agreed on, we
should begin to restore the damaged systems. The first
step to follow would be analyzing the current state, his-
tory, factors leading to damage the areas. We should es-
tablish some reference conditions for restoration, which
are based on a thorough study of historical ecosystem
structure and processes as well as on knowledge of eco-
logical relationships (ALCOZE
et d.,
2000). We should
not only compare with reference areas to estimate the
degree of degradation (BRINSON and RHEINHARDT,
1996), but also include an identification of the process-
es, which have led to degradation. This may not always
be obvious, because the effects of fragmentation
(DIGGELEN
et ~d.,
2001), long-distance hydrological
interference (GROOTJAN
et al.,
2001) and climate
change (KLOOR, 2000) are not clear. If we could not
analyze these thoroughly before carrying on restoration,
the projects of ecological restoration may be of no use,
and even some results may be catastrophic. For exam-
ple, the riparian forest project in San Diego (KUS,
1998) won a national prize from the Society for Ecolog-
ical Restoration, but the site subsequently dried out,
costly trees died, and upland plants invaded, because
the essential hydrology (river flooding) was not ensured
over the long term.
The next step should be to establish some scientific
strategies, using some ecological principles and other
knowledge, according to the goal and the analysis. Dif-
ferent goals need different strategies. But we found
there are some commons in these ways. As we know,
the usual phenomena of damaged areas are loss of bio-
diversity or worsen surroundings. The important restor-
ation strategies include two ways: one is the surround-
ings' restoration, the other is biological restoration.
Studies on the damaged areas on the earth indicate that
the major environmental problems may come from
soils: such as poor fertility, extremely physical and che-
mical conditibns, etc. Replacement of soil in the land is
therefore regarded as the most efficient method to alle-
viate adverse conditions ofsubstrates; if this method is
not available, other alternatives with lime, fertilizers,
organic manures, and others can be applicable. As what
the famous restoration ecologist--BRADSHAW said
that it was essential to concentrate on the soil and its
properties to achieve immediate results, otherwise there
Ecological Restoration:
would be immediate failure (BRADSHAW and CHAD-
WICK, 1980). In the meantime, the restoration of rivers,
lakes and wetlands had also been focus on. In the aspect
of biological restoration, species with strong resistance
and rapid growth, like grasses and herbaceous legume,
are always the first choice. These species can improve
the surroundings in some degree. We should try to in-
troduce native species into a damaged area, because ex-
otic species commonly compete with and replace native
species, which can have unforeseen negative conseque-
nces (CARLA and MEYERSON, 2002). Cares should
be taken to cause the least possible disturbance to in-
digenous species and soils as exotics are removed. In
some instances, non-indigenous plants are used for a
specific purpose in the restoration project, for example
as cover crops, nurse crops or nitrogen fixers. Unless
they are relatively short-lived, non-persistent species
that will be replaced in the course of succession, their
eventual removal should be included in restoration
plans.
After we apply these strategies to the damaged areas,
we should monitor and evaluate the result of restoration,
which can remedy our plans better. Unfortunately, mon-
itoring is rarely done, and when it is done, it often suffers
from poor design and lack of statistical rigor (BLOCK
et
d., 2001). In clarifying monitoring goals, a clear de-
scription of reference conditions should be stated,
preferably in quantitative terms. We should decide what
to monitor, according to the goals of ecological
restoration. A complicating factor in designing monitor-
ing programs is defining the appropriate variables to
measure wildlife response to restoration, such as spec-
ies, numbers, biomass, physical and chemical state of
soil, microclimate, and the change of underground water
(BERGER, 1991; XIA and CUI 2002). We contend that
monitoring restoration activities should always involve
experiments because researchers want to know not only
if there was an effect after restoration, but also whether
that effect was due to restoration or not.
if monitoring is conducted properly, results provide
information that can be used to evaluate and adjust
restoration practices. There are three strategies for con-
ducting an evaluation (http://www.ser.org): direct com-
parison, attribute analysis and trajectory analysis. In di-
rect comparison, selected parameters are determined or
measured in the reference and restoration sites. In at-
tribute analysis, quantitative and semi-quantitative data
from scheduled monitoring and other inventories are
useful in judging the degree which each goal has been
achieved. Trajectory analysis is a promising strategy,
still under development, for interpreting large sets of
Our Hope for the Future? 365
comparative data. In this strategy, data collected period-
ically at the restoration site are plotted to establish trends
to the reference condition. Under different views, the re-
sults of evaluation may be different. For example, the
restoration may appear to have been successful in eco-
logical terms, but not in aesthetic terms (SMALE
et al.,
2001). Whatever the strategy is, the purpose of monitor-
ing and evaluating is to ensure that the development of
the restored systems continue along the pathways as we
wish. However, ecological restoration is employed at
different scale, it would be impossible to monitor land-
scape-level restoration only through field experiments,
and managers cannot wait several decades, or hundreds
of years to decide which method to select. To make use-
ful prediction of the ecological consequences of a given
restoration project, computer simulation modeling can
play this role and enable us to assess landscape response
across large spatial and temporal scales (MLADENOFF
and BAKER, 1999; HE and MLADENOFF, 1999).
5 CONCLUSIONS
Restoration of degraded ecosystems is a relatively new
management approach, and effects of most restoration
treatments on various system processes and components
are poorly understood. Ecological restoration is a com-
plex process, which needs some kinds of professional
knowledge. Restoration ecology is developed from prac-
tices at the beginning, which is different from other sub-
jects of science (LAKE, 2001). Some theories in ecolo-
gy are derived from assumptions or quasi-experiments.
Ecological restoration can make up for the deficiency,
and provide a platform for examining these ecological
concepts and theories. Ecological restoration in the
world becomes more and more popular, mostly because
it satisfies the desire of people to amend the increasing
degraded systems. Dobson even regards restoration and
conservation biology as hopes for the future. Indeed, e-
cological restoration is becoming prominent in the disci-
pline of ecology.
However, ecological restoration has some faults. On
one hand, ecological restoration lacks sufficient theories
to support it. Almost all theories used by ecological
restoration come from other sciences, especially in ecol-
ogy, such as law of the minimum, law of tolerance, law
of energy, distribution pattern of population, succession,
and so on. Only self-design versus design theory comes
from restoration ecology (MIDDLETON, 1999). On the
other hand, the subjectivity of ecological restoration is
strong, because humans directly or indirectly determine
goals, methods and so on. Sometimes, the recognition
366
of structure, function, dynamic of degraded habits is not
sufficient. The goals set by humans are different, which
will result in the uncertainty of ecological restoration.
The goals established for ecological restoration should
include ecological, economic, cultural and political as-
pects, while some projects only emphasize ecological
aspect, regardless of other important aspects. Only all
aspects have been considered, the restored site will be
maintained for perpetuity. In addition, ecological rest-
oration is usually conducted on relatively small spatial
and temporal scales. However, ecosystems are not
closed systems within which all critical ecological pro-
cesses are incorporated, which allows ecosystems to in-
teract with others in the landscape through the move-
ment of energy, materials and organisms (PICKETT
and PARKER, 1994; PARKER, 1997). These large-
scale processes in conjunction with smaller, internal
processes determine the specific function of an ecosys-
tem in the landscape (PICKETT and PARKER, 1994).
The continuum of restoration efforts should be recog-
nized, ranging from restoration of localized highly de-
graded sites to restoration of entire landscapes for pro-
duction and/or conservation reasons (HOBBS and
NORTON, 1996; NAVEH, 1998).
Although the total frame for ecosystems to degrade
has been recognized, the further studies on the cause,
driving factors, process, and mechanism of degrada-
tion are still quite superficial, which are essential to re-
store and rebuild degraded systems. In all, we should
continue to absorb more knowledge from new theo-
ries, enhance our knowledge level, and expand our
views in order to better ecological restoration from all
aspects. If why to, what to, and how to restore degrad-
ed ecosystems are addressed effectively, ecological
restoration will get further progress in the new century.
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