Habitat Loss and Fragmentation
Fuente: Center for Biodiversity and Conservation
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
What is:
“Habitat Fragmentation” ?
The end result of human settlement
and resource extraction in a
landscape is a patchwork of small,
isolated natural areas in a sea of
developed land…
Gascon et al. 1999
Created by John Rozum, NEMO National Coordinator
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Habitat fragmentation can also be
thought of as “a disruption of
continuity”
Example: Forest Fragmentation
Source: Department of
Landscape
Architecture &
Environmental
Planning Utah State
University
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
1
Example: Wetland Fragmentation
Source: New York State GIS Clearinghouse
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Example:
Prairie
Fragmentation
Short-grass prairie
has been reduced
to < 0.1% of its
former extent
Source: J.S. Aber
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
What is a landscape?
Landscapes
„
„
An area that is heterogeneous
A mosaic where a mix of local
ecosystems and land uses is repeated
over space
2
3 basic landscape elements
„
Patch – recognizable area that contrasts with
adjacent areas and has definable boundaries
„
Corridor –connects two or more patches
„
Matrix – the “background” or dominate cover
type upon which patches and corridors occur
Corridor
Patch
Matrix
How large is a
landscape?
Landscape for an ant
Small bird
Does it apply to habitat
fragmentation?
What started us thinking about
certain landscape elements, like
patch size?
3
Island biogeography applied to habitat
fragmentation
fragmentation
reduces area
and increases
isolation
Wildlife communities in small woodlots are
• less diverse
• less abundant
Island biogeography and habitat fragmentation
Wildlife communities in large forested areas:
• more diverse
• more abundant
Habitat
loss
Habitat loss vs. fragmentation
„
Habitat loss – results in less habitat
for focal species or group
„
Fragmentation – technically, the
breaking apart of habitat (not always
with net loss)
…but they both usually occur together
Habitat
fragmentation
4
Landscapes are fragmented in a
fairly predictable fashion
The Fragmentation Process
Source: Gibbs et al. 1998
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Technical Terms for the
Fragmentation Process
Perforation - Holes
punched in a habitat
Dissection - Initial subdivision of continuous
landscape
Fragmentation - Breaking
up into smaller parts
Shrinkage - Reduction in
size of patches
Attrition - Loss of patches
Image source: Mark C. Wallace
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Created by John Rozum, NEMO National Coordinator
5
Another Example
Example of the Forest
Fragmentation Process
Moist Forest, Rondonia, Brazil 1975 - 1992
Source: http://www.cr.usgs.gov/earthshots/slow/Rondonia/Rondonia
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Temperate Hardwood Forest, Cadiz Township, Wisconsin, USA
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Forests,
Warwickshire,
England, Last
2000 yrs
Left: South-east Asian Tropical Deforestation is particularly severe, despite the region being the second only to the Amazon
for biological diversity: (a) India, Sri Lanka Almost all primary rainforest destroyed. (b) Thailand 45% loss between 1961
and 1985. Will lose 60% by 2000. (c) Malaysia Forest resources exhausted by 2000. (d) Indonesia 620,000 hectares / year.
(e) Philippines 55% forest loss 1960 - 1985. (f) Bangladesh All primary rainforest destroyed (Lean 67). Right: Sumatra
deforestation. (Groombridge)
Differences between Natural
and Anthropogenic Habitat
Fragmentation
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
But are natural environments not
already fragmented?
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
6
What then are the differences between
human-caused fragmentation and natural
“patchiness”?
(1) A naturally patchy
landscape has a
complex patch
structure, whereas
one fragmented by
humans has
simplified patches.
Missouri's Big Oak State
Park
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Faunal data from Amazon
„
Birds: 123 species
‰
(2) Many (but not
all) of the patch
types in human
modified
landscapes are
not suitable for
wild life.
‰
„
Frogs; 62 species
‰
‰
‰
„
‰
‰
4 use the matrix only,
15 forest interior only
10 use the forest edge
Ant species, 127 species
‰
‰
‰
(3) Because of (1)
& (2) there is
less contrast
between
adjacent
patches in
naturally patchy
landscapes and
therefore
potentially less
intense “edge
effects.”
16 use only the matrix
1 only in forest interior
51 in forest edge and interior.
Mammals: 15 species
‰
„
31 use matrix
92 that use forest edge or interior (none restricted to the forest
interior)
32 use matrix only
104 use the primary forest
44 use the forest edge
(4) Certain features of fragmented landscapes,
such as roads, are completely novel and pose
specific threats to wild species.
1900 versus 1990
7
Changes in the landscape…
Biological Dimensions of the
Fragmentation Process
„
The total area of available
habitat decreases,
„
The area of remaining
habitat patches decreases,
„
The number of remaining
habitat patches increases,
and
„
The connectedness of
remaining habitat decreases
(farther apart, more hostile
habitat in-between).
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Examples of “area-sensitive”
species: Neotropical migrant
songbirds of deciduous forests
of the eastern United States
Source: C. S. Robbins
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Species with large area requirements
„
Ivory-billed woodpeckers: ca.
7 km2 per breeding pair
„
male mountain lion (puma):
home range of 400 km2
„
Cerulean Warbler: 1000 ha
(a circle about 3.5km in
diameter)
Isolation affects Metapopulation
Viability – the “Connectivity” Issue
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
8
Probability of dispersing between
wetlands
Migration rates between patches as a
function of distances between patches
1
0.9
0.8
Mechanisms by which habitat
fragmentation reduces
metapopulation viability
„
Fragmentation reduces patch sizes
and population sizes, thereby
increasing extinction rates
„
Fragmentation increases inter-patch
distance and reduces migration
rates between patches, thereby
reducing the likelihood of local
populations sustaining one another
0.7
0.6
0.5
Reptiles
0.4
0.3
Amphibians
0.2
0.1
0
0
1000
2000
3000
4000
5000
6000
Inter-wetland distance (m)
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
The Rescue Effect
„
Immigration
from a large,
productive
subpopulation
can keep a
declining
subpopulation
from going
extinct
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Long-term effects of reduced patch
area and isolation on extinction
rates
From: Newmark.
W.D. 1996.
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Edge Effects
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
9
Edge Effects
Edge Effects: Depend on Patch
Shape and the Types of Adjacent
Patches
„
„
„
„
„
Area: 259 hectares
Edge: 11,771 meters
Area: 259 hectares
Edge: 6,748 meters
Microclimate changes
in light/temperature
Wind
Exotics
Fire
Hunting pressure by
humans and other
predators
Source: Department of Landscape Architecture & Environmental Planning Utah State University
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Fig. 2.
Predation rates
on artificial
nests decline
with distance
from a forest
edge. Edgerelated
predation
extends
300_600 m into
the forest (from
Wilcove 1985).
Fragmentation and Ecosystem
Function
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Fragmentation and Ecosystem
Change
•Plots deepest in the
interior of the remaining
fragments showed no
change in biomass.
•Those closest to the edge
lost as much as 5 tons of
biomass per hectare per
year, a rate of about 1.3%
per year.
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Edge Effects: Extent
Preserving Biodiversity in
Fragmented Landscapes
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Analysis and Planning
1.
2.
3.
Conduct a landscape analysis - where
are the big blocks and connections?
Evaluate the landscape in a regional
context
Can planning avoid further
fragmentation, e.g., via corridors?
11
km
km
89 k
m
91
Evaluating
fragment
isolation
and
scoping out
potential
corridors
43
Identifying Core Regions at the
Regional Scale
102
km
Source: Ersts, Center for Biodiversity and Conservation
Source: Ersts, Center for Biodiversity and Conservation
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Considering Edge and Patch Area
Issues for Reserve Design
Minimize negative edge effects
Source: Blair and Ballard 1996
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Do not ignore small fragments!
Corridors?
Invertebrates, seed sources, nuclei for
restoration
12
Butterfly Movements Through Corridors
Seed Dispersal Through Corridors
Potential Advantages of Corridors
„
More advantages
‰
‰
‰
Provide increased foraging area for wideranging species
Increased immigration rate to fragments could:
‰
increase effective population sizes of particular species
and decrease probability of extinction (provide a
"rescue effect")
‰
permit re-establishment of extinct local populations
‰
Reduce inbreeding depression and maintain genetic
variation within populations
Disadvantages
„
Provide predator-escape cover for
movements between patches
Provide alternative refugia from large
disturbances (a "fire escape")
„
Facilitate the spread of
‰
epidemic diseases,
‰
insect pests,
‰
exotic species,
‰
weeds,
‰
fire and other abiotic disturbances
("contagious catastrophes")
Increase exposure of wildlife to hunters, poachers,
and other predators
13
Example: The Effect of Implementing
a Prohibition on Riparian Zone
Clearing
(Source: Department of Landscape Architecture & Environmental Planning Utah State University)
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Evaluating Corridors and Connectivity
at the Regional Scale: The Proposed
Paseo Pantera
Evaluating Corridors and Connectivity at
the Regional Scale: Central Appalachian
Mountains
Source: The Wildlands Project
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Source: The Wildlife Conservation Society
Specific Recommendations for Minimizing
Fragmentation of Tropical Wet Forests
Guideline
Impact on Landscape
Avoid forest clearing within 150 m
of water courses
Enhances landscape connectivity,
protects water quality
Avoid clearing on steep (>30
degree) slopes
Retain forest remnants in sensitive areas,
reduce flooding and erosion
Avoid clearing rare vegetation types
Protect rare communities and seed
sources
Keep clearings to < 20 ha, Restrict
clearing of primary forest to < 50%
of property ownership
Reduces loss and fragmentation
Prohibit clearing or hunting within 1
km of protected areas
Reduces edge effects
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
(Source: Laurance & Gascon 1997)
Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for
Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum
Recent corridor experimentation
Damschen et al. 2006. Corridors increase plant species richness at large scales. Science 313:1284-1286.
14
Recent corridor experimentation
Habitat Fragmentation (End)
Damschen et al. 2006. Corridors increase plant species richness at large scales. Science 313:1284-1286.
15