INDICATOR ASSESSMENT
FOR
HABITAT FRAGMENTATION
Dr. Emilio Ortega Pérez. TRANSyT – Universidad Politécnica de Madrid
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
PRESENTATION INDEX
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FRAGMENTATION CONCEPT
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FRAGMENTATION EFFECTS
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INDICATOR ASSESSMENT FOR HABITAT FRAGMENTATION
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CONCLUSIONS AND RESEARCH NEEDS
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
PRESENTATION INDEX
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FRAGMENTATION CONCEPT
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FRAGMENTATION EFFECTS
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INDICATOR ASSESSMENT FOR HABITAT FRAGMENTATION
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CONCLUSIONS AND RESERACH NEEDS
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
FRAGMENTATION CONCEPT
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Fragmentation involves dividing up contiguous ecosystems (or
landscape unit) into smaller areas called “patches” (Forman, 1995)
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(1) increase of the number of patches,
(2) decrease of the mean patch size,
(3) increase of the total amount of edge
Reasons: human activity: deforestation, urban development or
transport infrastructures
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Fragmentation effects: Spatial and ecological
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
FRAGMENTATION: SPATIAL EFFECTS
Habitat
“A2”
Habitat
“A”
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Habitat
“A1”
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Area loss: new patch areas are
smaller
Patches shape are modified,
(depending on the action which
causes fragmentation)
Edge gain: new edges have
different conditions
Infrastructure §EDUULHU
Distance between patches
increase
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
FRAGMENTATION: ECOLOGICAL EFFECTS
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Less habitat surface
Patch isolation difficult interchange between individuals, and it
contributes to extinction of stabilized species
Edge effect: the dynamics of species interactions are altered and
permeability is increased
Barrier effect: Transport infrastructures are barriers to energy
and material fluxes and alter the resources of a habitat:
connectivity loss
THESE EFFECTS AS A RESULT OF HABITAT FRAGMENTATION HAVE
FAR-REACHING CONSEQUENCES FOR SPECIES SURVIVAL
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
FRAGMENTATION EFFECTS
Fragmentation chain of causality
Infractructure and traffic
Corridor
effect
More
connectivity for
some
metapopulations
Natural landtake
Less funcional
area for some
populations
Barrier
effect
Noise,
light
Less
connectivity for
some
metapopulations
Greenhouse
gases
Pollutans
Edge habitat
change
Habitat
change
Loss of
biodiversity
(Species richness)
Multiple interconnected chains
Cyclic chains
Impact is a non-linear sum of effects
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
Biota
collision
PRESENTATION INDEX
`
FRAGMENTATION CONCEPT
`
FRAGMENTATION EFFECTS
`
INDICATOR ASSESSMENT FOR HABITAT
FRAGMENTATION
`
CONCLUSIONS AND RESEARCH NEEDS
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
INDICATOR ASSESSMENT FOR HABITAT
FRAGMENTATION
FRAGMENTATION MEASUREMENT:
COMPOSITION, SHAPE AND CONFIGURATION (Rutledge (2003))
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Composition indicators describe the basic characteristics of
fragmentation
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Shape indicators attempt to quantify patch complexity
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Patch configuration indicators measure the degree of
connectivity or isolation between patches on a landscape
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
INDICATOR ASSESSMENT FOR HABITAT
FRAGMENTATION
COMPOSITION INDICATORS
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Composition indicators describe the basic characteristics of
fragmentation
The two basic indicators used to quantify fragmentation are
number of patches and patch area
Most species have minimum area requirements
Core area considerations
Limitations: area metrics have limitations imposed by the scale
of investigation
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
INDICATOR ASSESSMENT FOR HABITAT
FRAGMENTATION
COMPOSITION INDICATORS
Number
Expression
Number of patches, NP
(Turner et al., 1989)
Mean patch size, MPS
(McGarigal et al., 2002)
Largest patch index, LPI
(Saura and MartinezMillán, 2001)
Patch density, PD
(McGarigal and Marks
1995; Saura and
Martínez-Millán, 2001)
Si = area of patch
N = number of patches
St = total area of landscape
N = number of patches
St = total area of landscape
Description
Number of patches caused by
fragmentation
Average area of a patch of a
particular class
Percentage of landscape area
occupied by the largest patch of a
class
Number of patches per unit area
Average patch carrying
capacity, Kavg
(Vos et al., 2001)
Average of the number of
reproductive areas of a species in
the landscape
Core area (McGarigal and
Marks, 1995; Schumaker,
1996)
Core area inside a patch and
percentage of the patch that is
core area
Si = area of patch
Sc = area of core of patch
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
INDICATOR ASSESSMENT FOR HABITAT
FRAGMENTATION
SHAPE INDICATORS
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Shape indicators attempt to quantify patch complexity, which
can be important for different ecological processes
The primary significance of patch shape in a landscape seems to
be related to the ‘edge effect’
Most measures of patch shape focus on some variation of the
perimeter-area ratio
Limitations: the perimeter-to-area ratio method is relatively
insensitive to differences in patch morphology
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
INDICATOR ASSESSMENT FOR HABITAT
FRAGMENTATION
SHAPE INDICATORS
Number
Perimeter area ratio, P/S
(Krummel et al., 1987;
McGarigal and Marks,
1995)
Shape index, SI
(McGarigal and Marks,
1995; Schumaker, 1996)
Square pixel, SqP
(Frohn, 1998)
Expression
Description
Pi = perimeter of patch
Si = area of patch
Ratio of patch perimeter
to area
Pi = perimeter of patch
Si = area of patch
Ratio of perimeter to
area adjusted by a
constant
P = perimeter of patch Measures deviation from
SqP 1 (4 ˜ A )
A = square area a square shape
P
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
INDICATOR ASSESSMENT FOR HABITAT
FRAGMENTATION
PATCH CONFIGURATION INDICATORS
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Patch configuration indicators measure the degree of
connectivity or isolation between patches on a landscape
Connectivity is a vital element of landscape structure but it is
difficult to quantify and implement in practice
Distance-based configuration indicators: based on distance
between patches
Pattern-based configuration indicators: measure of distance
take into account landscape matrix resistance to movement
Limitations: that they require additional parameterization,
resistance coefficients
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
INDICATOR ASSESSMENT FOR HABITAT
FRAGMENTATION
PATCH CONFIGURATION INDICATORS
Number
Expression
Description
Nearest neighbour, dij
(Moilanen and Nieminen,
2002)
Relative size of the biggest
patch in the landscape, RSi
(Turner, 2001)
Connectivity index, CI
(Martín et al., 2007)
Distance from a
patch to the nearest
St = total area of landscape
Ri = Si/St (Si = area of patch)
Assess the
Sj = area of patch landscape resistance
Cij = distance between patches i,j
Cmax= maximum distance between patches
Patch cohesion (COH)
index (Schumaker, 1996)
0pi = perimeter of patch. ai = area of patch. N = total area of landscape
Integral index of
connectivity, (IIC) (PascualHortal and Saura, 2007)
Connectivity measure
between patches of a
class
nlij = number of links in the shortest path between patches i and j
ai and aj = area of patches
AL = total area of landscape
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
to be crossed by
species
Assess perimeterarea ratio of each
patch class in the
landscape
Connectivity measure
between two patches
in the landscape
INDICATOR ASSESSMENT FOR HABITAT
FRAGMENTATION
HABITAT CONNECTIVITY LOSS
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
INDICATOR ASSESSMENT FOR HABITAT
FRAGMENTATION
APPLICATION OF CRITERIA FOR THE CHOICE OF INDICATORS
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Validity: All indicators are based on the conceptual meaning of habitat fragmentation. The differences
between them depend on the degree of complexity with which they evaluate aspects of fragmentation.
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Reliability: As functions, the indicators are fully reliable.
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Sensitivity: Some of the indicators are very capable of revealing important changes in the factor of
interest. However, others are not sensitive to certain actions that cause habitat fragmentation.
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Measurability: It depends on the complexity of the indicator. Some of the indicators require complex
software and a lot of time for calculation because large amounts of information are taken into account.
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Data availability: They require digital maps. The data availability is high when the indicator is based only
on territorial structure, shape of patches, etc. It is low when the indicator is based on ecological
factors.
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Ethical concerns: No problem.
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Transparency: Most of the indicators are very transparent. Some of them are less transparent because
it is necessary to have some knowledge of ecological aspects.
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Interpretability: The interpretation could be difficult because some knowledge of ecological aspects is
required.
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Target relevance: the indicators are low in target relevance.
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Actionability: the indicators are low in actionability.
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
PRESENTATION INDEX
`
FRAGMENTATION CONCEPT
`
FRAGMENTATION EFFECTS
`
INDICATOR ASSESSMENT FOR HABITAT FRAGMENTATION
`
CONCLUSIONS AND RESEARCH NEEDS
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
CONCLUSIONS AND RESEARCH NEEDS
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In a territorial level, the land fragmentation and following loss of connection
between natural habitats (biodiversity loss, like last consequence) (McGarigal, 2001),
caused by infrastructures, are one of the most important impact.
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There are an important number of indicators to measure habitat fragmentation.
They measure different ecological aspects, have limitations and are complementary.
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The calculation of the indicators is complicated. An important database is needed.
Geographic Information Systems (GIS) is the most useful tool to calculate them.
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To evaluate the process of natural habitat fragmentation, there is a need to check
the real consequences of natural habitat fragmentation on biodiversity loss,
especially in large areas, and to evaluate the process of fragmentation in its global
(world) dimension.
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In parallel, the thresholds and standardizing criteria and indicators should be
defined.
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
Thank you for your attention!
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010
INDICATOR ASSESSMENT
FOR
HABITAT FRAGMENTATION
Dr. Emilio Ortega Pérez. TRANSyT – Universidad Politécnica de Madrid
COST 356 Final Conference. Indicator assessment for habitat fragmentation
Paris, 15 March 2010