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A Multicriteria Decision Analysis for Identifying Priority
Conservation Areas for Grassland Birds
Flavio Sutti1, Allan Strong1,*, and Noah Perlut2
Abstract - Biodiversity conservation frequently competes with the needs of society for
agricultural production and development. However, properly designed and efficiently
implemented conservation programs can be used to integrate wildlife and human needs.
We tested the efficacy of multicriteria decision analysis as a tool to select priority areas for
conservation in human-dominated landscapes using grassland birds in the northeastern US
as a test case. We created detailed GIS layers including landscape- (forest, grassland, development,
and roads within a 3000-m buffer around each grassland patch) and patch-level
(size, management, and conservation status) criteria important in grassland bird habitat
selection and conservation. We developed a set of 36 scenarios in which we varied the relative
weights associated with different patch attributes. A sensitivity analysis showed that the
habitat quality score for each patch was less sensitive to changes in weights at the landscape
level, and more sensitive to changes at the patch level. Integrating the GIS dataset into a
multicriteria decision analysis framework, we produced maps in which grassland patches
were ranked based on habitat quality and used these maps to identify priority conservation
areas. Grassland blocks of >100 ha were mainly concentrated in 2 regions and were identified
as priority sites that had the highest quality values for grassland bird conservation. This
approach resulted in maps that managers can use to focus conservation efforts. The integration
of GIS with multicriteria decision analysis can serve as a model for researchers to help
set priorities for land conservation for other species and in other regions.
Introduction
Conservation of biodiversity has been pursued traditionally by protecting
tracts of land with high biodiversity (Margules and Pressey 2000). However,
human domination of ecosystems is so pervasive that the conservation of
biodiversity cannot be achieved by setting aside land only for this purpose: there
is simply no more land to be protected that is not required for other functions
(Kareiva et al. 2007). Many species in need of protection, such as charismatic
megafauna and declining bird species, require large areas to maintain viable
populations. Thus, the conservation of healthy, functioning ecosystems in which
biodiversity is maintained in the presence of humans requires the integration of
reserve design rules and ecosystem management approaches at the species, ecosystem,
and landscape levels (Knight and Cowling 2007, Margules and Pressey
2000, Meffe et al. 2002).
1The Rubenstein School of Environment and Natural Resources, University of Vermont,
Aiken Center, 81 Carrigan Drive, Burlington, VT 05405. 2Department of Environmental
Studies, University of New England, 11 Hills Beach Road, Biddeford, Maine 04005. *Corresponding
author - astrong@uvm.edu.
Manuscript Editor: Jeremy Kirchman
24(Special Issue X):XX–XX
Natural History of Agricultural Landscapes
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Agricultural landscapes are examples of this approach, as the loss of native
prairie ecosystems has forced many species to use human-modified habitats
across significant portions of their range. One vertebrate group, grassland birds,
has shown consistent declines throughout North America (Cunningham and Johnson
2006, Herkert 1994, Perlut et al. 2008, Sauer et al. 2014, Walk and Warner
1999), with population declines >1.1% per year between 1966 and 2014 (Sauer et
al. 2014). At that rate of decline, total population sizes would be reduced by 50%
in less than 65 years. The decline of grassland birds is particularly significant in
the eastern United States where ~70% of these species are declining (Sauer et al.
2014). Multiple causes have been proposed to explain the decline of grassland
birds, but habitat loss and declining habitat quality are recognized as key elements
(Bollinger et al. 1990, Cunningham 2005, Herkert 1994, Perlut et al. 2008, Vickery
et al. 1994).
In the northeastern United States, grassland birds use agricultural fields and fallow
grassland patches for breeding habitat. Nearly all of these patches are found
on private land (Cuzio et al. 2013) and are managed in a variety of agricultural
schemes that may be at odds with conservation of grassland bird populations (Troy
et al. 2005). Thus, in this region, the conservation of grassland birds competes
with societal needs of agricultural production. As such, the goal of maximizing
biodiversity must be considered with the goal of minimizing costs to society to
make grassland habitat protection logistically, politically, and economically feasible
(Cameron et al. 2008). Several conservation programs offered through the
Natural Resources Conservation Service (NRCS) provide financial incentives to
landowners to improve habitat quality for grassland birds (NRCS 2008). However,
the programs are voluntary, and coordination and implementation have not been
applied in a spatially targeted manner that focuses on regions with high grassland
bird density. A systematic and repeatable method to delineate priority conservation
areas could maximize the conservation benefits of these programs .
We identified high impact areas for conservation of grassland birds by using multicriteria
decision analysis (MCDA), a framework that integrates manager objectives
with more-theoretical reserve design techniques (Belton and Stewart 2002). MCDA
is a procedure that uses objective criteria to evaluate a set of alternatives to reach a
meaningful and transparent solution. The core component of MCDA involves deconstructing
the problem into manageable components that are analyzed separately
and then integrated to obtain a solution (Malczewsky 1999). MCDA can combine
socioeconomic, ecological, and governance criteria and can involve collaborative
decision-making, thereby increasing the efficacy of conservation planning (Davies et
al. 2013, Meffe et al. 2002). Adding the spatial capability of geographic information
systems (GIS) offers a practical way to combine geographical data at multiple scales
to produce spatially explicit data for use in decision-making (Malczewsky 2006).
Although data are available on the relative abundance and distribution of grassland
birds for some areas, the information is often too sparse to be used in a reserve design
framework. By contrast, habitat data and management information are more readily
obtainable from a geospatial dataset or using remote sensing.
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Patch-level factors such as area, shape, and isolation are known to affect wildlife
populations. Grassland birds tend to favor large grassland patches and avoid
smaller fragments and patch edges (Helzer and Jelinski 1999, Herkert 1994, Keyel
at al. 2013, Vickery et al. 1994, Walk and Warner 1999). Landscape-level factors
such as roads, forests, agriculture, and urban development have also been shown
to have important negative effects on grassland bird population viability (Bakker
et al. 2002, Ribic and Sample 2001, Rodewald 2003). Additionally, the selection of
priority conservation areas should not solely rely on habitat and biological information
related to the target species, but should also account for the feasibility of
implementing management practices (Knight and Cowling 2007). Thus, successful
plan implementation requires the inclusion of characteristics that directly affect
the probability of conservation, such as current management objectives and level
of protection. Because the relative importance of these factors is unknown, MCDA
provides a framework for assessing the sensitivity of grassland patches to a diverse
set of criteria.
The identification and conservation of high-quality habitat for grassland birds
and the implementation of bird-friendly management in agricultural landscapes is
essential to reverse negative population trends of grassland birds and to conserve
grassland bird biodiversity. We used the Champlain Valley of Vermont as a case
study to test the efficacy of MCDA to select priority areas for species conservation
in human-dominated landscapes. Similar frameworks have been used by geologists,
engineers, and land-use planners for site selection for landfills (Sener et al. 2006),
and for the identification of areas vulnerable to contaminants (Lowry et al. 1995),
but we are aware of only one other study in which this framework has been used to
address a conservation issue (Phua and Minowa 2005).
Methods
Study area
The Champlain Valley (CV) is a 600,000-ha region in northeastern North
America surrounding Lake Champlain in Vermont and New York, and Quebec,
Canada. We worked in the Vermont portion of the CV. The land use/land cover of
the CV is 26% agriculture, 50% forest, 9% urban, 13% lakes and rivers, and 2%
wetlands (Troy et al. 2007). The CV has a relatively large amount of potential habitat
for grassland birds (130,000 ha including over 32,500 grassland patches) and is
situated in the Lower Great Lakes/St. Lawrence plain physiographic Bird Conservation
Region, which supports some of the largest populations of grassland birds in
eastern North America. These factors have led to grassland birds being targeted as
a conservation priority in the region (Jones et al. 2001, Rich et al. 2004).
Criteria and GIS analysis
The basis for our analysis was a vector layer that included all grassland patches
in the CV. This layer was derived from the United States Department of Agriculture
Common Land Unit boundaries data obtained from the Farm Service Agency
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(2008) and corrected using visual interpretation of remotely sensed imagery. These
patches are actively managed for agricultural production and represent permanent,
contiguous boundaries of fields with common land cover, management, and ownership.
All remaining grasslands were hand digitized from National Agriculture
Imagery Program (NAIP) orthophotographs. The Common Land Unit patches used
in this study were categorized as crop fields (corn, hay, other crops, or fallow),
and the hand-digitized patches were categorized as suburban/pasture (agricultural
pastures or large non-agricultural “suburban” fields).
We used patch-level and landscape-level components to rank grassland patches
for their importance to grassland birds. Within the patch-level component, we
identified 4 criteria: patch size, perimeter-to-area ratio, management intensity, and
conservation status. As grassland birds exhibit edge avoidance in nest placement
(Keyel et al. 2013, Perkins et al. 2013), patch size and perimeter-to-area ratio are
important attributes in assessing patch quality. Although area and perimeter-to-area
ratio values are correlated, we tested their effects independently on outcomes of
patch rankings. We considered conservation status and management intensity as human-
perceived criteria. Conservation status of the grassland patch addresses threats
from incompatible land uses (e.g., potential for development) where the application
of bird-friendly management may be less feasible. We assessed the conservation
status of each patch with a pre-existing protected-areas layer produced by the
Spatial Analysis Laboratory at the University of Vermont (VCGI 2008). This layer
included public and private parcels enrolled in any kind of conservation program.
Although parcels enrolled in conservation programs may not necessarily equate to
long-term protection, we assumed that landowners enrolling their property in any
conservation program would increase the probability for greater environmental
stewardship. We interpolated the conserved status layer with the grassland patch
layers to obtain a ranked value for each grassland patch on the basis of the proportion
of their area included in already protected areas. For management intensity, we
assigned a value of 1 to suburban/pasture patches because these areas are managed
less intensively. By contrast, all other agricultural patches were assigned a score
of 0 because these patches are in row crops (primarily corn) or are grass hayfields
or alfalfa hayfields that are cut 2–3 times during the nesting season (A. Strong,
unpubl. data). In the analysis, we maintained non-grassland agricultural patches because
they are often under crop-rotation management and could, at different times,
become high quality habitats for grassland birds. These patches also contribute to
the openness of the landscape (Keyel et al. 2013) and affect grassland bird settlement
patterns (Shustack et al. 2010).
For landscape components, we used 4 attributes: forest, grassland, development,
and roads. We used National Land Cover Database (NLCD) tree canopy
and impervious surfaces layers (Homer et al. 2004) and our grassland layer to
generate maps in which grassland patches were scaled on the basis of the amount
of forest, grassland, or developed habitat that was present within a 3000-m buffer
around each patch. The choice of a 3000-m buffer was based on landscape-scale
effects on habitat selection by Dolichonyx oryzivorus (L.) (Bobolink; Shustack et
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al. 2010), and breeding and natal dispersal distances of Bobolinks and Passerculus
sandwichensis (J.F. Gmelin) (Savannah Sparrow) in the Champlain Valley. For both
species, >90% of dispersal events were within 3000 m from their nest site (Cava et
al. 2016, Fajardo et al. 2009). More grassland in the landscape increased a patches’
criteria score, whereas patches with more forest and urban cover received lower
scores. We also categorized grassland patches on the basis of their distance from
roads centerlines (Vermont Center for Geographic Information 2009); we assigned
a value of 1 for patches >1200 m from highly trafficked roads (traffic volume of
≥30,000 vehicles/day), a value of 0 for patches 0–700 m from highly trafficked
roads, and (scaled) intermediate values for patches in between these distances (Forman
et al. 2002). We used a neighborhood analysis to summarize landscape values
at the raster level, and transferred the information to each patch using ArcGIS’s
zonal statistics.
Once quantitative scores for each criterion were generated, we standardized
them using a linear scalar transformation so all scores could be compared on a scale
from 0 to 1 (Malczewsky 1999). Consequently, each grassland patch had a numerical
score ranging from 0 (low quality) to 1 (high quality) for each of the 4 landscape
criteria and each of the 4 patch criteria. Because the factors that we quantified included
criteria at 2 spatial scales and factors (such as conservation status) that may
not affect grassland bird settlement decisions, we used 2 approaches to incorporate
this information into our prioritization of conservation decisions. First, we created a
set of 36 scenarios by varying the relative importance (i.e., weight) associated with
each of the attributes. This allowed us to quantify the effects of variation in landscape-
level vs. patch-level attributes, as well as vary the weights associated with
each of the criteria at both spatial scales. Second, we used the results from each of
the 36 scenarios to conduct a sensitivity analysis to quantify how robust each patch
was to variation in weighting schemes. Thus, we used variation in weights across
all of the scenarios to assess how each criterion affected the determination of patch
quality for grassland bird management.
The 36 scenarios that we assessed varied in the relative importance (i.e., weights)
applied to the landscape-level and patch-level components and among the criteria
within these 2 components (Table 1). These diverse scenarios allowed a wide spectrum
of possible outcomes. We altered the weights within the landscape-level and
patch-level components based on a literature review (as outlined in the preceding
section) and a survey administered to 7 grassland bird experts knowledgeable of
the study region. We structured the survey such that each criterion was compared
to all others within the same component (patch or landscape) using the pairwisecomparison
method (Saaty 1980). For this “expert scenario”, we used the survey
results to decide criterion weights, whereas for all the other scenarios, the weights
were determined by interpreting the literature. We calculated a consistency ratio
(here, our consistency ratio was less than 0.09, indicating moderate consistency), suggesting
that the comparisons used to calculate the weights were consistent within the
expert scenarios (Malczewsky 1999, Saaty 1980).
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Table 1. Variation in weights used in the 36 scenarios evaluated. [T able continued on next page.]
Description Weighting coefficient
Component-level strategies
ME Landscape component equal to patch component Landscape 0.50
Patch 0.50
Sum 1.00
ML Landscape component more important than patch component Landscape 0.75
Patch 0.25
Sum 1.00
MP Patch component more important than landscape component Landscape 0.25
Patch 0.75
Sum 1.00
Criteria-level strategies–LANDSCAPE component
EQUAL (LAND1) All criteria proportionally equal Grassland 0.25
Forest 0.25
Development 0.25
Roads 0.25
Sum 1.00
OPEN (LAND2) Openness of the landscape is prioritized Grassland 0.48
Forest 0.11
Development 0.11
Roads 0.30
Sum 1.00
EXPERT (LAND3) Expert opinion that prioritizes grasslands over other criteria Grassland 0.62
Forest 0.20
Development 0.11
Roads 0.07
Sum 1.00
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Table 1, continued.
Description Weighting coefficient
Criteria-level strategies–PATCH component
MANAGEMENT (PATCH1) Management criteria is prioritized Area 0.31
Management 0.58
Conserved 0.11
Sum 1.00
EXPERT2 (PATCH2) Expert opinion that prioritizes area over all other criteria Area 0.69
Management 0.24
Conserved 0.07
Sum 1.00
MANAGEMENT_R (PATCH3) Management is prioritized and perimeter-to-area ratio is used instead of area criteria Perimeter/area 0.31
Management 0.58
Conserved 0.11
Sum 1.00
EXPERT2_R (PATCH4) Expert opinion that prioritizes area over all other criteria (p erimeter/area ratio used Perimeter/area 0.69
instead of area) Management 0.24
Conserved 0.07
Sum 1.00
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Quality scores
We used variation in weights at the component (landscape-level or patch-level)
and criteria level (grassland, development, forest and road within landscape; patch
size, perimeter-to-area, management, and conservation status within patch) to
create quality scores for each patch across each of the 36 scenarios. The quality
scores were calculated by multiplying the patch’s score for each criterion by its
scenario-specific weight (Fig. 1); specifically, quality scores were the result of the
multiplication of weights by criteria within each component (component value =
Σwixi, where xi is the score for each parcel for the ith criterion and wi is the weight for
that criterion [Σwi = 1 and 0 ≤ wi ≤ 1]) and then summing the result of the multiplication
of weights by components (patch value = ΣwjLandscape + ΣwjPatch, where wj
is the weight for each component and landscape and patch are the component values
[Σwj = 1 and 0 ≤ wj ≤ 1]) (Malczewsky 1999). Quality scores for each patch ranged
from 0 to 1, and each patch received 36 quality scores, one for each scenario.
Figure 1. Analytical process for evaluating the quality of grassland patches in the Champlain
Valley of Vermont. The scenario illustrated above is one in which the patch component
is weighted more heavily than the landscape component (MP in Table 1). Within the patchlevel
component, the greatest weight is given to patch area criterion (PATCH2), and within
the landscape-level component, the greatest weight is given to the proportion of grassland
habitat within 3000 m of the patch (LAND 3).
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Sensitivity analysis
Using the results from the 36 scenarios, we ranked each grassland patch for
inclusion in priority conservation areas. We identified 5 quality classes: “very low”
(values 0 ≤ x < 0.2), “low” (values 0.2 ≤ x < 0.4), “medium” (values 0.4 ≤ x < 0.6),
“high” (values 0.6 ≤ x < 0.8), and “very high” (values 0.8 ≤ x ≤ 1). We assessed
the robustness of patches for grassland bird conservation based on their frequency
of occurrence in the high and very high quality categories across all scenarios.
We classified patches that scored high or very high in ≥18 of the 36 scenarios, regardless
of the weights attributed to criteria and components, as “good” patches.
Patches that scored high or very high in 9–18 of the 36 scenarios were classified as
“intermediate”, and patches that scored high or very high in less than 9 of the 36 scenarios
were classified as “poor”. By assessing the degree to which each patch was robust
to the criteria at the 2 scales, we removed some of the arbitrariness in the prioritization
scheme.
We used the kappa index of agreement (Landis and Koch 1977) to compare
among scenarios and 2 “null scenarios” in which all weights were kept equal.
This test statistic (Cohen’s Kappa) is used to evaluate inter-rater reliability and
was adapted for pair-wise comparisons of scenarios to determine the influence of
weights applied to components or criteria. Kappa values ≤ 0 indicate no agreement,
whereas values of 1 constitute perfect agreement.
Priority conservation areas identification
The output from the sensitivity analysis identified a robust set of individual
grassland patches for conservation; however, we wanted to identify patches in a
block or area to prioritize for outreach, conservation, and management. Several
methods can be used to select priority blocks, especially when considering the
many constraints that managers must address (e.g., willingness of owners to be
involved in some kind of management, pecuniary availability for purchase/protection
of particularly important areas, and/or connectivity to other patches). We used
Boolean operations in ArcGIS to identify 4 conservation scenarios. These examples
consider the need for blocks of grassland patches >100 ha to obtain greater species
richness. We applied thresholds to first aggregate good priority patches less than 10 m
from one another, and then aggregated both good and intermediate priority patches
less than 10 m from one another. We subsequently used these 2 thresholds to identify blocks
of patches >100 ha that could support breeding by grassland birds species known to
require large grassland patches in the northeastern United States (e.g., Bartramia
longicauda (Bechstein) [Upland Sandpiper]; Vickery et al. 1994).
Results
Across all scenarios, 23% of all patches (7538 of 32,724) scored high or very
high in ≥18 of the 36 scenarios and were therefore classified as good patches. Incremental
changes in the priority threshold between 13 and 23 showed 1.3–4.4%
changes in the total number of patches retained in the good category (Fig. 2A).
Thus, although 18 was chosen as a threshold arbitrarily, incremental changes in
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the threshold value had relatively minor effects on the number of priority grassland
patches, suggesting that overall, the classification scheme was insensitive to
changes in category ranges. We used Kappa index of agreement to compare the 36
scenarios from our model to 2 null scenarios. Scenarios that gave greater weights
to the patch-level criteria at the component level resulted in greater variation in the
total area in each quality class, and therefore decreased Kappa values (Fig. 2B). By
contrast, the total area in each quality class was more robust to changes in weights
within landscape-level criteria (Fig. 3B, C), and sensitive to changes in weights at
the patch (Fig. 3A) and component level (Fig. 3D, E). We compared each scenario
to every other scenario to assess congruence of ranking for each grassland patch;
low-, medium-, and high-value quality patches showed less congruence in ranking.
Very high quality and very low quality grassland patches scored consistently high
and low scores across all criteria, respectively, and were less sensitive to changes
in weights.
Using the perimeter-to-area ratio as opposed to patch area criterion shifted the
patch quality toward higher values (Fig. 2C). Furthermore, greater weighting of
the management intensity criterion was influential in increasing patch values. All
grassland patches that were part of the suburban pasture layer received a value of 1 for
the criterion management (average quality value for these patches was 0.595, versus
0.438 for intensively managed grassland patches; F(1,32722) = 24,511.59; P < 0.0001).
This high criterion score combined with its high weight in the (patch-level) management
strategy led to higher quality values in scenarios that included this strategy.
Our model classified 7538 out of 32,724 grassland patches as good (less sensitive
to variation in component and criteria weights), with habitat characteristics
attractive to grassland birds and greater potential to be enrolled in conservation
programs, totaling an area of ~33,600 ha (26% of the total grassland area). The good
grassland patches identified in the priority map (Fig. 4) were located predominately
in the southwestern portion of the study area, with a smaller block of good priority
patches present in the northwestern section of the map where agricultural activities
are more prominent.
The 4 examples of conservation blocks that we identified (Fig. 5) are one of the
multiple ways in which the GIS results can be used by managers to identify priority
Figure 2 (following page). Results of the sensitivity analysis. (A) Cumulative percent frequency
of number of patches that were included in the “good” category (>18) across all 36
scenarios. (B) Effect of component weights on congruence between scenarios using Kappa
index of agreement (+ 1 SE). Scenario labels are explained in Table 1. Greater weight in
the patch component reduces the congruence between pair-wise comparisons of the 36
scenarios with the null scenarios; (C) Averages of scenarios’ quality scores by patch-level
component strategies showing the effect of the weighting scheme. Scenarios in which management
had greater weight and perimeter-to-area ratio criterion was used instead of patch
area led to significantly greater quality scores (F3,32 = 22.29, P < 0.0001, n = 9) than the
expert strategies. See Table 1 for a description of the strategies and the weighting scheme.
Each box plot represents minimum, first quartile, median, third quartile, and maximum
value of the scenarios quality score average within each component strategy.
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Figure 2. [Caption on previous page.]
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conservation blocks. By aggregating patches less than 10 m from one another, we generated
34 to 114 priority conservation blocks >100 ha, and 17 to 53 of priority conservation
areas >200 ha.
Discussion
We combined GIS and MCDA to identify 2 key regions in which to focus
conservation efforts for grassland birds in the CV. In this framework, theoretical
Figure 3. Results of the sensitivity analysis assessing the effect of variation in weights at different
levels on the total sum area of patches (ha) in the 5 quality categories and controlling
for all other effects: (A) substantial variation between scenarios due exclusively to patchlevel
weights differences (scenario labels are explained in Table 1: s1 = LAND1 - PATCH1,
s2 = LAND1 - PATCH2, s3 = LAND1 - PATCH3, s4 = LAND1 - PATCH4); (B) limited
effect of variation in landscape level weights (area criterion used); (C) same as (B) but ratio
perimeter-area criterion used; note the change in the shape of the curve; (D) moderate
effect of variation in component level weights (ME = equal weights, ML = greater weight
to landscape component, MP = greater weight to patch component, area criterion used for
each); and (E) same as (D) but perimeter -to-area ratio criterion used.
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Figure 4. Priority map with patches classified into 3 categories. Each grassland patch was
categorized as either poor (scored in the high or very high categories less than 9 times across all
36 scenarios), intermediate (9–17 high or very high scores) or good (>18 high or very high
scores). The inset shows the town of Bridport to better illustrate patch quality variation at
a fine scale.
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Figure 5. Four examples of priority conservation areas for grassland birds obtained from the
priority map. In each map, patches separated by less than 10 m were aggregated. (A) Good patches
aggregated to create patches >100 ha. (B) Good and intermediate patches aggregated to
create patches >100 ha. (C) Good patches aggregated to create patches >200 ha. (D) Good
and intermediate patches aggregated to create patches >200 ha.
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reserve design techniques and management constraints were combined to prioritize
conservation and outreach activities. This approach integrated both landscape- and
patch-level attributes, and by tailoring the criteria to the species and habitats of
interest, it provided a practical framework for prioritizing conservation decisions
across our study region and can be applied to other regions or suite of species.
The maps we created used 8 criteria that incorporated both attributes of the site
as perceived by grassland birds, and anthropogenic characteristics. These criteria
offered the advantages of being easy to obtain or generate, applicable at the chosen
spatial scale, and easily modified to extract the desired data. The criteria provided a
robust assessment of patch quality, with both very high quality and very low quality
patches being insensitive to variation in weighting schemes. Consequently, the
priority conservation maps will allow managers to focus on a set of patches that
can provide benefits for grassland birds and will have a greater likelihood of being
enrolled in conservation programs. Patches with intermediate quality scores (low-,
medium-, and high-quality classes) were more affected by variation in weights because
their scores varied across criteria and their rankings were not as extreme as
for the patches identified as very high or very low quality (Geneletti and Van Duren
2008). Assessing how variation in weights affected patch quality scores is important
for understanding model sensitivity. For example, certain criteria had greater
impact in driving the characterization of good patches. Patches with a quality score
of 1 in the management criterion (32% of the total number of patches) generally
received greater scores in many scenarios; 51% of the patches that scored a 1 for
the management criterion were classified as good. The conservation criteria could
have had a similar effect as management, being almost a dichotomous categorical
criterion (with only 10% of the patches having quality scores between 0 and 1).
However, ~83% of the grassland patches were not included in conserved areas and
received a quality score of 0. Another criterion that contributed in shifting values toward
higher quality scores was the perimeter-to-area ratio. In the scenarios in which
we used the area criterion, most grassland patches received a fairly low value (many
patches in the CV are small with a few outliers). On the other hand, most grassland
patches received a high score when we used the perimeter-to-area criterion because
most agricultural patches are roughly square or rectangular. Consequently, even
small patches may receive high scores when the perimeter-to-area ratio is standardized.
Although the definition of a “patch” for a grassland bird is ambiguous, one
might consider a size threshold before applying a perimeter-to-area criterion. We
advise researchers to evaluate carefully the effect of each criterion in driving the
quality value of each patch. Particular attention should be used for dichotomous
criteria, such as management and the effect of standardization if the distribution is
skewed. The decreased Kappa scores associated with greater weighting on the patch
component was likely a result of incorporating 2 dichotomous criteria.
While our analysis was not comprehensive, it provided a streamlined starting
point for management planning that is more likely to be applicable than one that
is over-parameterized (Malczewsky 1999). For the sake of practicality, parsimony,
and simplicity of the model, the criteria were not exhaustive in including all factors
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that are known to influence grassland bird habitat selection or probability of conservation.
However, additional factors could be easily incorporated into the analysis.
For example, information on soil, vegetation, inter- and intraspecific interactions,
current management regimes, and socio-economic factors connected with agricultural
activities are variables that may influence the habitat selection decisions of
grassland birds. Further, quality values for cost of patch acquisition, level of involvement
of each landowner, and perceived stakeholder value for each patch, once
available, could all be included to add a socio-economic component to the analysis.
To minimize the potential arbitrary nature of some criteria scores (Game et al.
2013), we used past studies to generate the criteria incorporated and assessed a
wide range of weighting schemes in addressing sensitivity across criteria. We did
not correlate these criteria directly with grassland bird density or reproductive
success. Instead, the goal of our study was to produce a map showing the greatest
potential for cost- and time-effective investment in grassland bird conservation. For
example, although grassland birds are significantly more likely to settle in large
patches, hayfields that are cut 2–3 times in the growing season will have no Bobolink
and limited Savannah Sparrow reproductive success (Perlut et al. 2008). Thus,
a large, intensively managed field does provide potential habitat, but was penalized
for the low probability of incorporating bird-friendly management practices. As a
result, these fields would not be prioritized in outreach activi ties.
Other advantages of this approach
The involvement of experts in the selection of criteria and their weights can improve
the quality of the final results (Geneletti and Van Duren 2008). We involved
grassland bird experts in the selection of the criteria to include in our model, asking
them to compare pairs of criteria and decide which of the 2 was more important.
Scenario s12, in which both landscape and patch weights were determined with the
help of the experts, provided the highest Kappa value when component weights
were equal. This result supports the involvement of experts starting early on in the
process of criteria selection. The same methodology could be used as new criteria
become available, enlarging the panel of experts or opening it to additional stakeholders
to offer further perspectives in the decision process (Geneletti 2007).
Although more spatial datasets are available in raster format, the vector dataset
used here provided several advantages. Utilizing a vector-based spatial dataset,
combined with information on the management of grassland parcels, provided a
more precise delineation of the grassland patches with up-to-date information on
management practices. Such precision cannot be obtained using a raster-based
approach. The advantages of using parcel-based maps included ease of tracking
changes in patch shape and simplicity of joining additional information to the spatial
dataset for statistical analyses.
Limiting our analysis to grassland patches also provided some advantages over
other approaches. In many reserve-design scenarios, constraints are used to exclude
unsuitable habitat from the analysis (Carrion et al. 2008, Malczewsky 1999,
Sener 2004). Because only potential habitat was included in the spatial dataset, we
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2017 Vol. 24, Special Issue 8
excluded constraints from the analysis, thereby simplifying the analytical process.
Cost criteria, included in our analysis, were standardized using a “reverse” formula
that gave lesser values to the patches that have greater costs for the criterion
analyzed. Patches with standardized values of zero for certain criteria were not
automatically excluded as unsuitable patches as done by using a constraints framework,
but a zero value contributed to lowering the overall quality score of a given
patch. This process can also be used to rank focal conservation areas both on the
basis of their quality for the species considered and for their potential for cost- and
management-effective initiatives.
Reserve maps produced using Boolean selection operations provided one means
to visually summarize the delineation of a reserve system. We based the selection
process of priority conservation areas on threshold sizes of 100 and 200 ha as suggested
by Vickery et al. (1994). These large blocks (for the northeastern US) were
also chosen considering that the size of a reserve is correlated to the number of
species that it can support (Diamond 1975), and the fact that most grassland species
are area sensitive and some, in particular the Upland Sandpiper, require large
continuous grasslands (Houston and Bowen 2001). The priority conservation areas
(Fig. 5) depicts a robust system of high quality habitat distributed in the southern
portion of the study area where most of the agriculture in the CV is located. If grassland
birds are distributed as a metapopulation, this spatial arrangement of blocks
should allow exchange of individuals between patches. Generation of reserve maps
offers a versatile way for researchers to apply thresholds, incorporate information
at different scales than the one used for criteria maps, or include raster-level data
that cannot be easily summarized in a vector-based format.
The integration of MCDA and GIS is a valuable framework for prioritizing
conservation and management decisions. The maps should be considered as the
“foundation” on which the conservation of grassland birds can be built. Managers
and stakeholders can apply this tool to help guide outreach for promoting conservation
and alternative management practices where they should have the greatest
chance of success. The methods used to generate the priority maps and the tools
created in ArcGIS can be thought of as “blue prints” that can be copied as is or
modified for specific needs in identifying priority conservation areas. The versatility
of MCDA and the spatial capability of the methodology applied in this study
to identify priority conservation areas for grassland birds can be easily modified
to address specific needs for different species, guilds, taxa, communities, and/or
locations. Diverse stakeholders can be involved in the decision process. Priority
maps, resulting from the multicriteria decision analysis can be used for designing
reserves and planning at broad spatial scales. Because resources for conservation
activities will always be limited, methodologies for increasing the efficiency of
conservation work will always be necessary.
Acknowledgments
We thank J. O’Neil-Dunne, E. Buford, and A. Troy for their GIS help. We are grateful
to T. Donovan for comments and suggestions on how to improve this manuscript.
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T. Alexander, J. Buck, M. Fowle, M. Labarr, and R. Renfrew provided expert assessment of
factors influencing grassland bird habitat selection.
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