Ecological Risk

Ecological Indicators 41 (2014) 133–144
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Ecological Indicators
journal homepage: www.elsevier.com/locate/ecolind
Ecological risk assessment of wetland ecosystems using Multi Criteria
Decision Making and Geographic Information System
B. Malekmohammadi ∗ , L. Rahimi Blouchi
Graduate Faculty of Environment, University of Tehran, P.O. Box 14155-6135, Tehran, Iran
a r t i c l e
i n f o
Article history:
Received 18 October 2013
Received in revised form 25 January 2014
Accepted 29 January 2014
Keywords:
Ecological risk assessment (ERA)
Risk factor
Risk zoning
Risk management
Iran – Shadegan Wetland
a b s t r a c t
Nowadays, wetlands are at risk from a wide range of stress factors. Practical application of wetland
ecological risk assessment will result in a better understanding of how physical, chemical, and biological stressors impinge on wetlands and will provide a framework for prudent wetland management. An
important aspect of wetland management is to identify ecological risks affecting the area and to develop a
wetland-zoning map based on those risks. This study uses a process of ecological risk assessment (ERA) to
identify stress factors and responses within the framework of an ecosystem-based approach. All potential
environmental factors, physical, chemical and biological need to be examined in context. This study aims
to present a systematic methodology for risk assessment and zoning of wetland ecosystems. Initially,
the most important risks threatening wetlands are identified in an ecosystem-based approach. Endpoint
assessments are defined according to values and functions of the wetland and the ecological risks associated with these endpoints are identified. In the characteristics step, risks are analyzed according to
severity, probability and a range of consequences. A Multi Criteria Decision Making (MCDM) method is
used to prioritize these risks on the basis of experts’ opinions. Geographic Information System (GIS) is
used to develop a zoning map with a combination of risk layers according to importance. Finally, management strategies are proposed to deal with the risks. The proposed methodology was applied to Shadegan
International Wetland, located in southwestern Iran. This wetland is in the Montero list and is currently
threatened by various risks. According to the results, high-ranking potential risks and areas with different
levels of risk and management strategies were proposed for this wetland.
© 2014 Elsevier Ltd. All rights reserved.
1. Introduction
Wetlands are one of the three major types of ecosystem on
the Earth; they are formed through the interaction of land and
water systems and provide an irreplaceable ecological service
as an ecosystem for human society (Zedler and Kercher, 2005;
Kim et al., 2011). Wetland ecosystems have an important role
in maintaining biological diversity, they are also important for
biochemical transformation, storage, production of living plants
and animals and for decomposition of organic materials (USEPA,
2002; Clarkson et al., 2003). Wetlands have been exposed to a
range of stress-causing alterations from activities such as dredging
and filling operations, hydrologic modifications, pollutant runoff,
eutrophication, impoundment, and fragmentation by roads and
ditches (Klemas, 2011). These activities cause disruption to the
ecological balance of animal and biotic reservoirs in wetlands
(Ramsar Convention Secretariat, 2004).
∗ Corresponding author. Tel.: +98 21 61113185; fax: +98 2166407719.
E-mail address: [email protected] (B. Malekmohammadi).
1470-160X/$ – see front matter © 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.ecolind.2014.01.038
The spread of urbanization and industrialization has escalated
wetland degradation in many parts of the world, in both developing and developed countries (Tiner, 1984; Holland et al., 1995;
Dahl, 2000; Ralph, 2003; Zedler and Kercher, 2005). Previous studies of wetland protection focused mainly on the functioning of
constructed wetlands, ecological water demands and vegetation
development (Spieles, 2005; Chen et al., 2009; Cui et al., 2009).
For different kinds of wetlands, changing environmental flow is
an important risk factor that needs to be considered when undertaking ecological restoration and management of water resources
of basins (Yang and Mao, 2011). Agricultural use and industrial
production, pesticide residues, contamination of wetlands from
chemicals outlets, change in natural habitats, over exploitation
of natural resources, have caused potential risks to the wetland
ecosystems. There is a need for tools to assess the ecological condition of wetlands for a range of purposes, including Environmental
Impact Assessments (EIA), ecological reserve determinations and
the planning and monitoring of wetland management and rehabilitation outcomes (Kotze et al., 2012).
Recently, ecological risk assessment (ERA) has applied several tools for modeling. Ecological modeling has been used in
other fields such as water quality modeling (Chau, 2007; Wu
134
B. Malekmohammadi, L. Rahimi Blouchi / Ecological Indicators 41 (2014) 133–144
and Chau, 2006; Muttil and Chau, 2006). ERA evaluates the likelihood of potential adverse effects on ecosystems as a result
of exposure to one or more stress factors (USEPA, 1992). Currently, ecosystem-oriented models of ERA have proved efficient
in evaluating structural and functional responses within a variety of ecosystems to enable better environmental management
(Christian et al., 2009; Chen et al., 2010, 2011). Applications of
ERA include assessments that range from screening-level (qualitative) to detailed (quantitative) or a combination of both (i.e. tiered
ERA); predictive to retrospective in temporal scale; local to global
in spatial scale; and single threat to multiple threats (USEPA, 1998;
Burgman, 2005). ERA involves examining an area’s environmental conditions by means of environmental risk assessment analyses
that consider various aspects of the hazards as well as the vulnerability and specific environmental values of the studied area under
(Heller, 2006).
ERA of wetlands involves estimating potential hazards or threats
posed by stressors (chemical, physical, or biological) to biotic
and/or abiotic components of the wetland. This assessment forms
the information base that drives important environmental management decisions on a local, national, and international levels
worldwide. Practical application of this tool will result in a better
understanding of how physical, chemical, and biological stressors
impinge on wetlands and will provide a framework for prudent
wetland management. An important aspect of wetland management is to identify ecological risks affecting the area and to develop
a wetland-zoning map based on those risks. Wetlands can be
viewed as complex temporal and spatial mosaics of habitats with
distinct structural and functional characteristics. Because of the
unique characteristics of wetlands the key stressors and receptors
in the wetlands under study should be clearly identified and, if
necessary, prioritized in order to guide the risk assessment process. Risk characterization requires an understanding of the major
external and internal factors regulating the operational conditions
of a wetland. Furthermore, an ecosystem-based approach involves
determining links between these factors and identifying the way in
which stress factors affect the wetland.
Lemly (1997) examined the ERA of wetlands as a managerial
tool. The study developed an ecosystem-based approach toward
risk assessment in freshwater wetlands. Suter (2000) presented
an argument for developing generic assessment endpoints in ERA
that measured the ecological characteristics essential for protection
against risks by quantification, measurement and modeling. Kellett
et al. (2005) provided an analysis of ERA workshops for wetlands
of the Lower Burdekin, and recommended strategies for the execution of ERA for irrigation planning and assessment. Hanson et al.
(2008) evaluated ecological functions of the wetlands. This project
demonstrated that assessment of wetland functions provides key
information for wetland environmental assessment.
Wang and Cheng (2011) applied ERA in zoning of the Baiyangdian Basin in China. Using Geographic Information System (GIS) and
Remote Sensing (RS) technology, a region-wide environmental risk
visualization was produced that enhanced the effectiveness of environmental risk management. Zhang and Huang (2011) employed
a GIS-based multi-criteria method to evaluate potential nitrogen
loss at the basin level, and applied the model to the Huai River
Basin. The results helped to examine the complex responses of wetland systems to changes in land use under different socio-economic
circumstances.
A review of previous ERA studies reveals that the most recent
studies have used structural features and functions of wetlands
as valuable and important ecological features. Chen et al. (2013)
reviewed state-of-the-art models that were developed for ERA and
presented a system-oriented perspective for holistic risk evaluation and management. They concluded that assessing ecological
risk with system-based models at different levels of organization
in a combined way, presents an evolutionary step for application
of risk evaluation in environmental management.
This study presents a systematic methodology in an ERA for wetland ecosystems to identify stresses and responses. The method
used in this study applies all physical, chemical and biological
stress factors affecting the environment in a semi-quantitative risk
assessment approach. For this purpose, the most important environmental risks are identified. In the characteristics step, risks are
analyzed according to severity, probability and range of consequence. These indicators are then used to determine scope and
extent of each risk. The determinations of proposed measures to
be applied in environmental control were made from gathering
experts’ opinions. Analytical Hierarchy Process (AHP) is used to
prioritize risks. A zoning map of risks threatening the wetland is
developed using GIS. This map identifies wetland parts according to
level of risk to achieve optimum planning with an ecosystem-based
approach. Finally, management strategies are proposed to deal with
these risks. The methodology has been subsequently applied to
Shadegan International Wetland, located in the southwest of Iran.
This wetland is in the Montero list and is now threatened by various
factors.
2. Methodology
A framework was developed for assessing the ecological risks
for wetland areas using a semi-quantitative approach. Semiquantitative methods are used to describe the relative risk scale.
For example, risks can be classified into categories like “very low”
“low”, “moderate”, “high” and “very high”. In a semi-quantitative
approach, different scales are used to characterize the likelihood
of adverse events and their consequences. Analyzed probabilities
and their consequences do not require accurate mathematical data
(Radu, 2009). In semi-quantitative methods, risk indicators and values are determined according to information on real available data
as well as using judgments made by experts. Fig. 1 presents a structural illustration of the methodology applied to wetland ecological
risk assessment. This structure was formed with a combination of
risk assessment technique, the AHP method and the GIS tool. The
method was according to the following steps:
Step 1: Identification of ecological endpoints and ecological risks
associated with these endpoints. In order to set the ecological endpoints, according to the International Conversation
Nature and Natural Resources (IUCN) booklet (Dugan,
1990), the most important wetland values and functions
and the main related endpoints are identified. Assessment
endpoints are the functions and associated values that need
to be protected, enhanced, or created through risk management (Lemly, 1997). The focus of ecological endpoint
assessment is to determine ecological endpoints that are
threatened (Pastorok et al., 2002).
Step 2: Risk characterization step. In this step risks are analyzed
according to severity, probability and consequence. A risk
index is calculated by analyzing severity, exposure and
probability (SEP) in a semi-quantitative approach with Eq.
(1).
Risk = Probability of the risk × range of consequences
of risk × severity of the risk
(1)
In Tables 1–4, severity, probability, range of consequences and range of risks are classified from very low
to very high with scoring according to that taken from a
review of related literature, engineering judgments and
information gathered from brainstorming sessions with
B. Malekmohammadi, L. Rahimi Blouchi / Ecological Indicators 41 (2014) 133–144
135
Fig. 1. Framework of the methodology in the wetland ecological risk assessment.
Table 1
Classification and scoring of the severity in the wetland ecological risk assessment.
Table 2
Classifying range of the consequences in the wetland ecological risk assessment.
Expected consequence
Scores range
Class
Wetland exposed area (portion of total area)
Class
Destroying the integrity and
existence (5)
Changes in the hydrological
balance and regime (4)
Disruption of the biological
balances (3)
Changes in physical and
chemical parameters (2)
Disruption of the
biogeochemical cycles (1)
15–13
Very high (5)
12–10
High (4)
All of the wetland and the surrounding ecosystems
Three quarter (¾)
Half (½)
One quarter (¼)
Less than one quarter (¼)
Very high (5)
High (4)
Moderate (3)
Low (2)
Very low (1)
9–7
Moderate (3)
6–4
Low (2)
<4
Very low (1)
a group of experts. The determined environmental risks
are given a score for severity by applying an assessment
of consequences of each potential risk. Expected consequences are identified through assessment of the ecological
endpoints. In Table 1, classification and scoring of the severity of wetland risks are developed by cumulative impact
assessment of consequences in the wetland. Summation of
numbers in the first column is equal to 15. Classes of severity are ranked from very high (5) to very low (1) and each
class is assigned a score up to 15.
Scores evaluating the consequences of each risk are performed by identifying the wetland area exposed to the risk.
In Table 2, classification range of consequences of risks is
done according to the wetland areas that are affected by
the risks. The probability of a wetland ecological risk is
classified according to probability of the expected consequence (Table 3). By applying Eq. (1), amounts are given
Table 3
Classifying of the probability in the wetland ecological risk assessment.
Expected probability
The likelihood of the
consequence
Class
Certain (risks occur
continuously)
Common (risks occur
usually)
Possible (risks may occur
from existing risks)
Likely, but are low
Very likely
Very high (5)
Greater than 50%
High (4)
Equal to 50%
Moderate (3)
Unlikely under normal
conditions
Impossible or remote
under normal
conditions
Low (2)
Likely, but are very low
Very low (1)
as an evaluation of each risk. Table 4 presents the range,
classification and description of risks.
Step 3: After identifying risks, they are prioritized on the basis
of their importance. This can be done according to the
classification of severity, probability and consequences
of the risk. These criteria should be valued in risk
136
B. Malekmohammadi, L. Rahimi Blouchi / Ecological Indicators 41 (2014) 133–144
Table 4
Classification and description of the risks in the wetland ecological risk assessment.
Risk range
Classification
Description
125–101
100–76
75–51
Very high
High
Moderate
Unacceptable
Unacceptable
Acceptance with
conditional control
Acceptable
Negligible
50–26
<26
Low
Very low
assessment according to degree of importance and influence. Multi-criteria Decision Making (MCDM) is used to
prioritize risks and effective indicators to estimate risk
levels. MCDM were applied in different EIA and ERA
studies such as Zhao et al. (2006) and Zhang et al.
(2009). MCDM is a class of decision-making methodology based on the premise of assisting a decision-maker
through the decision process via explicit formalized models
(Figueria et al., 2005). Belton and Stewart (2002) and Kiker
et al. (2005) presented a review of the available literature
and provide some recommendations for applying different
MCDM techniques. These include the AHP, ELimination and
Choice Expressing the REality (ELECTRE), Multi Attribute
Utility Theory (MAUT), Preference Ranking Organization
METHod for Enrichment Evaluation (PROMETHEE), and
various combinations of these methods.
AHP is a theory of measurement through pairwise comparisons that relies on the judgments’ of experts to derive
priority scales (Saaty, 2008). In this study, AHP is utilized. A
hierarchical structure of a target is used to find important
weights for each wetland ecological risk. Pair-wise comparison matrixes in AHP are used to weight the indexes
and options of the risks based on experts’ opinions. Risk
prioritizing has been used to make proposals for corrective action to reduce risks. It should be noted that other
methods such as ELECTRE, MAUT, PROMETHEE can also
be applied in ERA for wetlands. Each of them has their
advantages and disadvantages as evident from a series of
regular debates in prominent journals. The advantages of
AHP over other multi-criteria methods, as often cited by
its proponents, are its flexibility, intuitive appeal to the
decision-makers or experts, and its ability to check the
inconsistencies in judgments (Saaty, 2000). AHP helps to
elicit the complex judgments of different experts in a common platform. It also ensures accuracy in the sense that it
has an inbuilt method to check the inconsistency of judgments. This ensures that the judgments are provided only
with sufficient care and the error due to negligence is thus
minimized (Ramanathan, 2001).
Step 4: All risk factors must be spatially modeled, they need to
appear on the map as points, lines, polygons or raster models. Man-made landscape features such as agricultural and
urbanized areas, tourism zones and hotels, roads, industrial
areas, also surrogate indicators such as population density
can be included as human impacts and these are determined by experts and used as risk factors. The combination
Fig. 2. Location and specification of the Shadegan Wetland and related basin in Iran.
B. Malekmohammadi, L. Rahimi Blouchi / Ecological Indicators 41 (2014) 133–144
of risk elements and their assigned risk parameters may
vary for each habitat in order to account for the different
ways in which human activities impact on biodiversity in
each realm (McPherson. et al, 2008). Wetland zoning is used
as a management strategy done to identify areas with highranking risk. GIS evaluates the ecological risks of human
activities and natural disasters, which are the main factors
that contribute to change on wetland ecological indexes.
Using the GIS tool, the zoned wetland risk map is developed.
Information layers are required for the main risk factors.
These layers are overlaid according to the weights obtained
from AHP. Weights are assigned to the layers using the
Raster Calculator in Spatial Analyst functions and weighted
linear combination (WLC) is used to overlay the weights.
WLC is one of the most widely used methods of MultiCriteria Evaluation (MCE) for analysis of land suitability.
It involves standardization of suitability maps, assigning
weights of relative importance to the maps, and combining weights and standardized suitability maps to obtain an
overall suitability score (Malczewski, 2004). WLC analysis
was based on Eq. (2).
S=
Wi Xi
(2)
where S is the zoning map of the wetland, Wi is the weight of
layer i obtained from AHP, and Xi is the standard raster layer
i. According to the zoning map, area zones with different
levels of risk are determined.
Step 5: Finally, risk management strategies will be provided for
high-risk zones. The most effective risk management
strategies are presented within wetland basin, because
wetlands are associated and interacted with upstream and
downstream processes.
3. Study area (Shadegan International Wetland, Iran)
Shadegan International Wetland is located in southwestern Iran,
in Khuzestan Province, between 48◦ 20 –49◦ 20 E longitude and
30◦ 50 –31◦ 00 N latitude. Fig. 2 shows the geographical location
and specification of the study area. The cities of Ahwaz, Abadan,
Mahshahr and Shadegan are the main population centers around
the wetland. This wetland is located in the Jarahi River Delta with
very flat land and low-gradient plains’ topography. The Jarahi basin
is located in southwestern Iran and southern parts of the Zagros
Mountain Range. The basin area is about 24,310 km2 . The Shadegan
Wetland is about 537,731 ha, of which almost 61% is protected as a
Wildlife Refuge (Environmental Protection Agency of Iran, 2010).
This natural wetland has important hydrological, biological and
ecological significance in terms of maintaining normal functions of
the basin and coastal system. There are more than 100,000 water
bird species with five of the world’s rare species of bird in this
wetland. The unique diversity of this wetland includes plant and
animal species specific to freshwater, brakish and saltwater environments. Specifications of different parts of the Shadegan Wetland
are given in Table 5 (Pandam Consulting Engineers, 2002; Shadegan
City Department of Environment, 2010). As can be seen in Fig. 2 and
Table 5, the Shadegan Wetland consists of three distinct parts:
(1) A freshwater zone, which is located in the upper part of the wetland. This area is fed by the Jarahi River and has lush vegetation
cover.
(2) A tidal zone, which is located in the southern part of the wetland (downstream of the Abadan-Mahshahr highway). The area
is influenced by the tides of the Persian Gulf and involves multiple waterways (estuaries). Upstream freshwater is mixed with
downstream saltwater as freshwater passes through the land.
137
Table 5
Different regions of the Shadegan Wetland (Pandam Consulting Engineers, 2002).
Shadegan Wetland
zones
Freshwater
Tidal
Coastal (Mosa
estuary)
Other and marginal
lands
Total
Total
Wildlife Refuge
Area (ha)
Percent
Area (ha)
120,378
222,252
115,978
22.4
41.3
21.6
75,310
252,455
–
23
77
–
79,123
14.7
–
–
327,765
100
537,731
100
Percent
(3) The coastal zone or saltwater wetland, which includes the Persian Gulf coastline to at the water depth of 6 m. The Mosa
estuary and several small islands are also in this area.
Wetland vegetation is a vital characteristic of such an environment, it is important in terms of sustainability of the ecological
and economic values of the wetland. The Shadegan Wetland, in
addition to its global value was granted status as Wildlife Refuge
by the Iran Department of Environment. Table 5 presents freshwater and tidal zones of the Wildlife Refuge areas in the wetland.
The most significant human activities affecting the Shadegan Wetland are those of dam construction and irrigation projects in the
Jarahi catchment, oil and gas platforms, industrial projects, infrastructure projects, exploitation of wetland resources and tourism.
Recently, human activities such as water pollution, indiscriminate exploitation of biological products of the wetland, drought
and change in natural habitats have directly or indirectly affected
the wetland functions (Rahimi Blouchi, 2012). This wetland is
in the Montero list and is now threatened by several risks.
Despite its unique values, this wetland is now far removed from
Table 6
Assessment of ecosystem functions and values of Shadegan Wetland (Behan Dam
Consulting Engineers, 2010, according to IUCN booklet, Dugan, 1990).
Function
Values
Statues of
values in
Shadegan
Wetlanda
Hydrologic flux and
storage
Groundwater recharge
Groundwater discharge
Flood control and protection
Water supply
䊉
Biological productivity
Food storage
Forest resource
Wildlife resources
Aquatic
Forage resources
Agricultural resources
Historical and cultural
resources
䊉
䊉
Biogeochemical cycling
and storage
Stabilize the shoreline/erosion
control
Sediment control/toxic
materials
Protection from storm/wind
break
Wastewater treatment
Water quality
Biodiversity
Tourism/recreation
Preservation of flora and fauna
(refuge)
Threatened, rare, and
endangered species
䊉
Community/wildlife
habitat (ecological)
䊉
a
() absent or exceptional, (䊉) present, () common and important value of
wetland.
138
B. Malekmohammadi, L. Rahimi Blouchi / Ecological Indicators 41 (2014) 133–144
Table 7
Characteristics of the risk factors in Shadegan Wetland.
Risk factor
Harmful potential effects
Receivers
Range of consequences
Drought/low water
occurrence
- Reduction in productivity and
survival of the wetland
- Reduction of hydrological
stability
- All organisms in the soil and
aquatic life
- Humans dependent to
wetland
All of the wetland and the
surrounding ecosystems
High temperature and high
evaporation
- Increase of chemical and
biological functions’ rates
- Reduction in species richness
All organisms in aquatic life
Freshwater zone
Salinity of wetland water
- Reduces denitrification,
biological uptake and
photosynthesis
- Diminishes species richness
All organisms in the soil and
aquatic life
- Freshwater zone
- Tidal zones in the south of
Abadan – Mahshahr road
Sedimentation and filling
- Depresses biological uptake,
processing and photosynthesis
- Diminishes species richness
- Reduces groundwater
recharge
- Changes in sediment particle
size
All organisms in the soil and
aquatic life
Freshwater zone (sediment
entrance from the northern
rivers)
Over exploitation of
natural resources
- Increases erosion potential
- Establishment of invasive
species
- Reduces the interception,
condensation, evaporation and
surface roughness - Reduces
sediment stabilization
Organisms dependent to
natural resources
- Freshwater zone (The vicinity
villages)
- Northeastern Wildlife Refuge
Entrance of agricultural
and livestock wastewater
- Short-term: increases
productivity
- Long-term: encourages
invasive species, decreases
species
- Reduces diversity and
production
- Enhances adsorption of some
chemicals
- Eutrophication
- All organisms in the soil and
aquatic life
- Humans dependent to
wetland
Freshwater zone (from
northern part)
- All organisms in the soil and
aquatic life
- Humans dependent to
wetland
Freshwater and tidal zones
(from industries on the north
and northwest)
Entrance of rural and urban
waste water
- Diminishes habitat suitability
- Reduces photo-oxidation and
increases denitrification rate
- All organisms in the soil and
aquatic life
- Humans dependent to
wetland
Freshwater and tidal zones
(from central and southwest)
Oil pollution
- Biological magnification
- Soil pollution and
contamination of groundwater
- All organisms in the soil and
aquatic life
- Humans dependent to
wetland
- Northern boundary of the
Wildlife Refuge
- A part of tidal zone in
southern
Change in flow regime
- Reduces in water inflow
- Reduces in water flow
purification
- All organisms in the soil and
aquatic life
- Humans dependent to
wetland
Freshwater zone
Change in natural habitats
- Reduces groundwater
recharge
- Increases evapotranspiration
- Increases concentration of
inorganic
All organisms in the soil and
aquatic life in wetland
All of the wetland and the
surrounding ecosystems
Road construction
- Reduces biodiversity
- Disturbing hydrological flows
- Reduces the water quality
- Habitat loss
All organisms in the soil and
aquatic life in wetland
- Northern part
- North of the Wildlife Refuge
Entrance of industrial
wastewater
its natural condition. This study aimed to identify and manage the most stress inducing risks that threaten the wetland
and to maintain its ecological balance and to protect the study
area.
4. Results and discussion
Prior to modeling an ERA, it is important to identify previously
developed information for the wetland under consideration in the
study. Information from aerial photographs, historical maps and
land-use documents are useful for gaining an understanding of the
history and status of an area. It is also important to gain an understanding of the hydrologic and geologic forces affecting a wetland.
Understanding a wetland’s function and determining its values is
an important part of ERA for wetlands. These function–value relationships provide an important conceptual framework that can
formulate the operation’s goals and objectives.
Application of ERA methodology on the Shadegan Wetland
firstly used important values and functions of Shadegan Wetland
to determine endpoints. Assessment of the Shadegan Wetland in
B. Malekmohammadi, L. Rahimi Blouchi / Ecological Indicators 41 (2014) 133–144
139
Table 8
Results of calculation of the risks in the Shadegan Wetland.
Risk factor
Severity
Range of
consequence
Probability
Risk level
Importance
weight in
AHP
Weighted
risk
Risk
ranking
number
Drought/low water occurrence
High temperatures and high evaporation
Salinity of wetland water
Sedimentation and filling
Over exploitation of natural resources
Entrance of agricultural and livestock wastewater
Entrance of industrial wastewater
Entrance of rural and urban waste water
Oil pollution
Change in flow regime
Change in natural habitats
Road construction
4
2
4
5
4
4
4
4
4
4
4
4
5
2
3
2
3
3
4
4
3
5
5
3
3
5
5
4
5
5
5
5
5
4
4
5
60
20
60
40
60
60
80
80
60
80
80
60
0.064
0.090
0.061
0.056
0.098
0.072
0.087
0.082
0.089
0.099
0.12
0.082
3.84
1.8
3.66
2.24
5.88
4.32
6.96
6.56
5.34
7.92
9.6
4.92
9
12
10
11
5
8
3
4
6
2
1
7
terms of its ecosystem functions and values was done according
to the method cited in the IUCN booklet by Behan Dam Consulting Engineers (Behan Dam Consulting Engineers, 2010). The
booklet includes field studies and information on environmental characteristics of the wetland and this information was used
to complete the IUCN checklist for values of the Shadegan Wetland. Results of this assessment are presented in Table 6. Then,
the most important ecological endpoints were identified according
to these values and functions. All of the parameters (hydrological
and ecological) that were considered critical to long-term sustainability of the wetland were considered as possible ecological
endpoints. Biogeochemical processes such as hydrological regime,
primary productivity (food web stability), biodiversity (abundance,
species richness), sensitive and natural habitats, integrity and
existence of wetland, were determined as the most important endpoints.
Risks and stressors imposed on Shadegan Wetland were identified in accordance with the ecological endpoints and shown in
Table 7. This table describes harmful potential effects, receivers
and the range of consequences for each risk factor. The most important consequences of determined by evaluation of risk factors were
identified as destroying the integrity and existence of the wetland,
changes in its hydrological balance and regime, biological imbalance, changes in physical and chemical parameters and disruption
of biogeochemical cycles of the wetland.
The risk factors threatening Shadegan Wetland were analyzed
according to step 2 of the methodology and are presented in Table 8.
The information shown in Table 7 was used to calculate severity,
probability and to determine the range of consequences for each
risk from the step that evaluated risk analysis. According to the
severity index, drought (low water occurrence), sedimentation and
over exploitation of plant resources of the wetland were evaluated as having the greatest level of risk (very high). Also, factors of
high temperatures and high evaporation were evaluated as having
the lowest level of the risk. According to the consequence index,
drought, change in flow regime and change in the natural habitat were evaluated as having the greatest amount of risk (very
high). In addition, factors of high temperatures and high evaporation, gradual sedimentation and filling and over exploitation of
plant resources of the wetland were evaluated as having the lowest
level of risk (low). According to the probability index, almost all of
the stressors have continuous impact and as such are associated
with a very high level of risk.
Table 8 shows calculations of risk level based on Eq. (1). Results
of risk calculation for each of the risk factors show that almost all
of the risks were evaluated as having high and medium level risk.
Table 8 shows the industrial wastewater outlets, rural and urban
waste-water outlets, and changes in natural habitats that were had
the maximum degree of risk. Also, the lowest amounts of the risk
were calculated for factors of high temperatures and high evaporation. Results of sensitivity analysis on the risk assessment values in
Table 8 show the evaluations for elimination of the criteria ‘range
of consequence’, ‘probability’, and ‘severity’ that contribute to a
change in risk level of about 31.4, 22.4, 26 and risk ranking numbers
of about 91%, 41.7%, 8%, respectively. These evaluations show the
importance of considering these three criteria, especially that of
Fig. 3. Hierarchical structure of ecological risk assessment of Shadegan Wetland.
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B. Malekmohammadi, L. Rahimi Blouchi / Ecological Indicators 41 (2014) 133–144
Fig. 4. Risk zoning layers for risk factors in Shadegan Wetland. (a) High temperatures and high evaporation, (b) salinity, (c) over exploitation of biological resources, (d) water
pollution, and (e) change in natural habitat
B. Malekmohammadi, L. Rahimi Blouchi / Ecological Indicators 41 (2014) 133–144
141
Table 9
Percentages of categories in each layer in the ecological risk zoning of Shadegan Wetland.
Category of risk
Very high
High
Moderate
Low
Very low
Risk factor
High temperatures and
high evaporation
Salinity of
wetland water
Over exploitation of
natural resources
Water
pollution
Change in natural
habitats
Final zoning
map
10.07
7.67
6.37
5.48
70.41
6.9
5.9
6.22
4.25
76.7
5.54
1.05
2.25
17.02
86.44
12
15
33
30
10
16.59
8.81
5.87
7.82
60.91
10.4
11.56
14.88
44.09
19.07
‘range of consequence’ in wetland ecological risk assessment. Also,
variation evaluations for these three criteria show changes of up
to 27% but evaluations for risk level and risk ranking number are
stable. These evaluations demonstrate an acceptable level of stability in calculations of risk values in the proposed methodology for
wetland ecological risk assessment. Sensitivity analysis on importance of weights, based on average weights, shows that risk ranking
number is dependent on about 33.3% in terms of importance
weights.
A hierarchical structure of the ecological risks, according to the
indexes of the risks (severity, range of consequences and probability) is shown in Fig. 3. Information on experts’ opinions was
used to weight the criteria and alternatives of the risks through
Pairwise Comparison according to the hierarchical structure. In
this study, national experts were selected from different organizations in the region. There was a lack of communication and
understanding between the wetland community and those doing
the risk assessment in the study region. It is essential that those
individuals that contribute to process of wetland ecological risk
assessment have a common understanding of some basic principles from both disciplines. Thus, access to experts with scientific
knowledge of the area was difficult in this particular case study. In
total, contributions from the opinions 15 experts were considered
and confirmed by the AHP Consistency Ratio. Five environmentalists, five water resources experts, and five agricultural experts
were used in brainstorming session and to answer a questionnaire.
Expert Choice software (www.expertchoice.com) was used for calculations of AHP weights. Final weights of AHP for the risk factors
are presented in Table 8. Risk factors were prioritized by multiplying risk level and importance weight of each risk. Rankings of
risks are shown in the last column of Table 8, and represent the
priority of each risk factor, for the wetland. Based on these priorities, change in natural habitat factor was high ranking factors and
sedimentation and filling factor was low ranking factors.
Fig. 5. Ecological risk zoning map for Shadegan Wetland.
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B. Malekmohammadi, L. Rahimi Blouchi / Ecological Indicators 41 (2014) 133–144
Table 10
Management strategies (control measures) for reducing effects of risk factors in Shadegan Wetland.
Risk factor
Risk level
Affected zone
Management strategies (control
measures)
Category
Rating
Change in natural habitats
High
1
All of the wetland and
surrounding ecosystems
- Developing a legal regional
binding guideline to prevent land
use changes
- Avoid or minimize wetland
disturbance by applying wetland
setback regulation
Change in flow regime
High
2
Freshwater zone
- Allocating the minimum of water
rights
- Restricting unauthorized
exploitation of the rivers,
especially in drought periods
- Implementation of integrated
water resources management at
the Jarahi basin
Entrance of industrial
wastewater
High
3
Freshwater and tidal zones
- Industrial wastewater treatment
- Continuous monitoring of
wetland water quality and
applying water quality standards
Entrance of rural and urban
wastewater
High
4
Freshwater and tidal zones
- Keeping the canebrakes in the
entrance
Over exploitation of natural
resources
Medium
5
Freshwater zone and
Northeastern of Wildlife
Refuge
- Identifying the capacity of grazing
and harvesting of hays and straws
- Establishing buffer strips for
arable lands
- Developing wetland operation
guidelines
Oil pollution
Medium
6
Northern boundary of the
Wildlife Refuge and a part of
tidal zone
- Insulating the oil transfer pipes
Road construction
Medium
7
North part of wetland and
north of the Wildlife Refuge
- Constructing culverts
- Maintaining the wetland habitat
corridors
Entrance of agricultural and
livestock wastewater
Medium
8
Freshwater zone
- Controlling the time and amount
of using agricultural materials
Drought/low water occurrence
Medium
9
All of the wetland and
surrounding ecosystems
- Designing a drought monitoring
network in the Jarahi Basin
Salinity of wetland water
Medium
10
Freshwater and tidal zones
- Usage of halophyte plants
- Transfer of agro-industrial
complexes of saline drainage water
to Persian Gulf (at 6 m depth of sea)
Table 8 shows changes in natural habitats, changes in upstream
flow regimes (such as dam building in the catchment of Jarahi),
industrial wastewater outlets, rural and urban wastewater outlets,
over exploitation of natural resources of the wetland, oil pollution,
agricultural and livestock wastewater outlets, road construction in
and around the wetland, and drought occurrence in recent years
were determined as the main risks threatening the Shadegan Wetland respectively.
Based on the importance of risk factors and available information, five layers were selected for consideration in wetland
ecological risk zoning. Change in natural habitat, water pollution
(by wastewater outlets), over exploitation of biological resources,
salinity of wetland water, and high temperature and high evaporation are the layers that were developed in ecological risk zoning.
Wetland risk-zoning layers were produced using spatial analyst
tools in Arc-GIS 9.3 software (Environmental Systems Research
Institute ESRI, 2008). Each layer was reviewed, classified and ranked
according to the degree of threat that was considered for each in
relation to the habitat or species in question. Data in the past 10
years were used for developing the layers. These layers are presented in Fig. 4 and explained according to the following:
(1) High temperature and high evaporation (Fig. 4a): due to high
temperature, the greatest influence was on the shallow parts of
the wetland. To produce this layer, water depth in the freshwater zone was used as an index. Water depth in different parts of
the wetland varied from a few centimeters to about 3 m. Zoning of the wetland was done with regards to the adverse effects
of high temperature on wetland flora and fauna. Shallow parts
were determined as having a high level of risk and the deep
parts with lower levels.
(2) Salinity of wetland water (Fig. 4b): This map was produced from
data on electrical conductivity of wetland water in the freshwater zone. Electrical conductivity changed at different parts
of the wetland water ranging from 1.4 to 21 dS/m. Those parts
with high salinity were considered as high risk and vice versa.
(3) Over exploitation of natural resources (Fig. 4c): the likely extent
of impact of the over exploitation are considered as zoning
criteria. The buffer extension in GIS software was used to produce this map. The influence of distance for direct and indirect
impacts was considered at 50 and 2000 m, respectively. In locations that had been over exploited, distance of the buffer zone
increased from the centers of points, lines or polygons. Areas
B. Malekmohammadi, L. Rahimi Blouchi / Ecological Indicators 41 (2014) 133–144
with risk level ranked as very high and high were those of freshwater wetland in the vicinity of villages due to road access roads
in those areas.
(4) Water pollution (Fig. 4d): Data on source pollution and entrance
points to the wetland were used to develop this layer. The main
sources of water pollution were those of upstream irrigation
development projects, the sugar cane industry in the northern
part of wetland, petrochemical activity in Mahshahr, shipping,
carbon and steel industries in Ahvaz, Maroon desalination,
wastewater from surrounding cities and villages in the east
area of freshwater wetland and burst pipes that leaked oil into
the wetland. Wastewater outlets from agricultural and livestock farms, industrial, rural and urban areas, and oil pollution
were considered in this layer. Due to lack of data on amounts
of pollution concentrations in the wetland, sources of pollution and their relative entrance points; these values were rated
according to experts’ opinions, judgments of engineers and
information collected from field studies. Industrial pollution,
rural and urban pollution, oil pollution, agricultural and livestock pollution and other pollutions were rated as very high,
high, moderate, low, and very low, respectively. The Spatial
Analyst interpolation was used in GIS software to produce this
layer. The Spatial Analyst interpolation was used in GIS software
to produce this layer.
(5) Change in natural habitat (Fig. 4e): This layer was prepared
from a map of existing land-use in the wetland. Zoning was
done according to the influence distance of change in land-use.
The influence distance was determined as the spatial extent
or footprint of change in the natural habitat on the wetland
and represents the maximum distance at which a feature has
a negative impact on the wetland. For example, adverse effects
of roads within the wetland’s ecological range were considered
to have a range of impact extending to 1000 m (Forman et al.,
2003). The influence distances for direct and indirect impacts
were considered as 200 and 1000 m, respectively. The buffer
extension was used in GIS software to produce this map. The
zones that were evaluated as having very high and high levels
of risk were in areas disturbed by human activities.
Percentage of categories in each layer that were used for ecological risk zoning of the Shadegan Wetland are given in Table 9. Based
on Step 4 of the methodology, by applying importance weights from
Table 8, the final ecological risk-zoning map of the Shadegan Wetland was produced and is shown in Fig. 5. As can be seen in this
figure, the area that was evaluated with the least risk was that of
the southern wetland in the saltwater area, probably because it
was a pristine environment inaccessible to humans. Evaluations
determined the area most at risk was the northern area of the wetland, a freshwater area with access roads that facilitated of human
access to the wetland. This map enables decision makers and environmental planners to regulate human activities in and around the
wetland.
Results of sensitivity analysis on the final risk-zoning map show
that classification of the final risk-zoning map did not change
with variation of important weights of up to 30% change, on
these weights. These results show acceptable stability in classification of risk-zoning layers. In addition, the final risk-zoning map
was sensitive to the elimination of each layer and more sensitivity was observed for elimination of the layer representing over
exploitation. Based on the results of risk analysis and the ecological risk-zoning map, strategies to manage and reduce the ecological
risks of Shadegan Wetland are abstracted in Table 10. The proposed
management strategies for the wetland were determined by the
above-mentioned ecosystem-based approach. In Table 10, risk factors were ordered according to the ranking number of each risk
143
from Table 8. Zones relating to each risk factor are described with
regards to the risk-zone maps.
5. Conclusions
Development projects such as road construction, thermal power
plants, transmission lines, oil and petrochemicals and factories
threaten the life of wetlands. In order to protect and manage
wetlands in a sustainable way, it is necessary to reduce ecological risks that impact on the wetlands. The best approach toward
applying ERA in wetland studies is ecosystem-based management.
In this study, an ecosystem-based approach was considered to
present a methodology for identifying and characterizing risks and
to develop management strategies. Experts’ opinions were used to
prioritize risks according to the AHP. A zoning map of the risks that
threaten the wetland was developed using GIS.
Risk zoning is an important measure in environmental risk management. It involves dividing an area into sub-areas according to
general risk characteristics. Identifying the similarities and differences of risk factors between sub-areas by making comparisons
between sub-areas can help to determine the most appropriate
environmental risk management policies. The GIS that was used in
this article constitutes a powerful tool for decision-makers in conservation to establish preferences, which need to identify human
activities in terms of spatial interactions and other factors that
influence the health and viability of critical habitats and key species
in a wetland.
ERA can provide a description of the actual situation of ecological, health status or risks that threaten wetlands. The presented
methodology can be redeveloped to apply to different types of
wetlands to identify and manage the risks. This method focuses
on identification of wetland endpoints and conservation of values
associated with these endpoints. This target is obtained by identification of hazards/threats to values of the wetland endpoints.
Results of this study for Shadegan Wetland reveal that the stressors inflicted on the environment of this wetland causes adverse
effects on characteristics of the wetland. Alteration in natural habitats, changes in the water balance of wetland, water pollution,
over exploitation of biological resources, and drought are the main
stressors of this wetland. All of these factors are interrelated and
due to the complexity of wetland ecosystems, it is difficult to separate the effects and consequences of these factors.
For Shadegan Wetland, management strategies are suggested on
the basis of the results of this research. Preventing change in wetland land-use, providing sufficient water for the wetland, ensuring
water quality of the wetland, protecting biodiversity, sustainable
use of wetland resources, increasing awareness of wetland values
and threats, and promoting public participation are the main goals
of the proposed strategies. Most threats in the study area were
found to be in the northern region and in areas of freshwater that be
attributed to the existence of access roads in such areas that facilitate increased human access to the wetland. The lowest risk zone
was identified in the southern part of the wetland in a saltwater
region that is a pristine environment inaccessible to humans.
The key stressors and receptors in a wetland under consideration must be clearly identified in order to make properly targeted
risk assessment and to provide useful data. However it is very difficult to assess and determine the threshold of permitted reserves
of these resources and to identify stress factors in those wetlands,
in which potential reserves of biological components do not have
any scientific data or documentation. Further development of the
proposed methodology can focus on risk assessment of wetland
functions to manage the activities that reduce capacity of the wetland ecosystem. Assessment of wetland functions through standard
quantitative risk assessment can be used to restore wetlands and
144
B. Malekmohammadi, L. Rahimi Blouchi / Ecological Indicators 41 (2014) 133–144
to improve environmental assessment programs. Quantitative risk
assessment of wetlands can focus on chemical substances (such as
nutrients and contaminants) by only incorporating assessments of
toxicity. In this kind of assessment, indicators such as pollution concentration at outlet points and diffusion in a wetland, the impact
of wastewater on the food chain, and concentrations of metals or
other pollutants in soil and water are used for making assessments.
It should be noted that this study has examined major risk factors
of environmental impacts on the wetland but cumulative impacts
of these risk factors have not been considered. Clearly, more work
needs to be done on the development of a holistic environmental
risk assessment for wetlands that includes qualitative and quantitative risk assessment approaches.
Acknowledgments
The authors would like to thank the two anonymous reviewers,
for their constructive comments on correction and improvement of
the manuscript. Contributions by Ms. Azadeh Zarkar, Ph.D. student
of the University of Tehran are hereby acknowledged.
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