1. Habitat Fragmentation
"Let's start indoors. Let's start by imagining a fine Persian carpet and a hunting knife. The carpet is twelve feet by eighteen, say. That gives us 216 square feet of continuous woven material. Is the knife razor sharp? If not, we hone it. We set about cutting the carpet into thirty-six equal pieces, total them up--and find that, lo, there's still nearly 216 square feet of recognizably carpet like stuff. But what does it amount to? Have we got thirty-six nice Persian throw rugs? No. All we're left with is three dozen ragged fragments, each one worthless and commencing to come apart."
Note that the cut-up carpet metaphor is imperfect since habitat fragmentation necessarily entails both habitat reduction and change in habitat configuration.
Quote from David Quammen’s (1996) Song of the Dodo; Image from

2. Habitat Fragmentation
Habitat fragmentation is an anthropogenic disturbance
Disturbance – a discrete event that removes biomass (and thereby can create heterogeneity or “patchiness”)
Photo of a fragmented Valdivian forest in Chile from:

3. Habitat Fragmentation
Habitat fragmentation is an anthropogenic disturbance
with two components:
(1) A reduction in area of the focal habitat type
(2) A change in habitat configuration; remaining patches are smaller and more isolated than in the original configuration
Photo of a fragmented Valdivian forest in Chile from:

4. Nature is Inherently “Patchy” & Dynamic
“Water, earth, and fire are Louisiana’s three special ingredients…
The lowlands flood. The uplands burn… if you live in Louisiana,
there are only two possibilities: either your land will eventually flood,
or it will eventually burn. Most of our native plants and animals are
therefore dependent on either flooding or fire or, in some cases, both.”
Paul Keddy
(b. 1953)
Photo of Paul Keddy from quote from Keddy’s (2008, pg. 14) Water, Earth, Fire

5. Nature is Inherently “Patchy” & Dynamic
Space-time Mosaic (Watt 1947); Shifting Mosaic (Bormann & Likens 1979); Patch Dynamics; Crazy Quilt (H. S. Horn)
Natural disturbance regime
F. H. Bormann & G. E. Likens Pattern and Process in a Forested Ecosystem. Springer, New York.
D. H. Deutschman, S. A. Levin, C. Devine, & L. A. Buttel Scaling from trees to forests: analysis of a complex simulation model; advertised in: Science 277:1623.
A. S. Watt Pattern and process in the plant community. J. Ecol. 35:12-22.
Green = Eastern hemlock
Purple = American beech
Red = Red maple
Yellow = Yellow birch
500 yr
1000 yr
Images from Deutschman et al. (1997);

6. Nature is Inherently “Patchy” & Dynamic
Nature is inherently “patchy,” but anthropogenic disturbance often results in landscapes different from (and potentially
less hospitable than) those resulting from natural causes
Natural disturbance regime
D. H. Deutschman, S. A. Levin, C. Devine, & L. A. Buttel Scaling from trees to forests: analysis of a complex simulation model; advertised in: Science 277:1623.
Anthropogenic clearcut
500 yr
1000 yr
Images from Deutschman et al. (1997);

7. Nature is Inherently “Patchy” & Dynamic
Nature is inherently “patchy,” but anthropogenic disturbance often results in landscapes different from (and potentially
less hospitable than) those resulting from natural causes
Fragmentation reduces the extent and connectivity of habitats
Fragmented landscapes typically have simplified internal structure of patches and matrices
Fragmented landscapes typically have more contrast between
adjacent patches (including patch-matrix juxtaposition)
Features of fragmented landscapes (e.g., roads and dams)
pose special threats to population viability

8. Patch (Fragment) Size & Isolation
Log10 (No. species)
van der Werff, Henk (1983) Species number, area and habitat diversity in the Galapagos Islands. Vegetatio 54:
Log10 (Area)
Data for Galapagos plants from van der Werff (1983) Vegetatio

9. Patch (Fragment) Size & Isolation
Diamond (1972), who compared species richness on islands with that expected for an island “near” (< 500 km) a “mainland” source; “Mainland” = New Guinea; Islands = Bismark Archipelago.
See: Jared Diamond Biogeographic kinetics: Estimation of relaxation times for avifauna of southwest Pacific islands. PNAS 69:
Data for Bismark Archipelago birds from Diamond (1972) PNAS

10. Patch (Fragment) Size & Isolation
Island Biogeography Theory emphasizes
dynamism & patchiness of natural processes
Conservation Biologists (and managers) must understand natural processes, to make sense of anthropogenic disturbances
and to restore ecological / evolutionary processes
Joint consideration of area and distance led to the Equilibrium Theory of Island Biogeography (Munroe 1948; MacArthur & Wilson 1963, 1967; for a good description see Gotelli 2001, chapter 7).
A key assumption of the model is that there is a permanent mainland source pool of species from which colonists are drawn.
Robert MacArthur ( )
E. O. Wilson (b. 1929)

11. Island Biogeography Theory
Concerns the dynamics of immigration from a mainland
source pool and extinction on islands or patches
surrounded by inhospitable matrix
Joint consideration of area and distance led to the Equilibrium Theory of Island Biogeography (Munroe 1948; MacArthur & Wilson 1963, 1967; for a good description see Gotelli 2001, chapter 7).
A key assumption of the model is that there is a permanent mainland source pool of species from which colonists are drawn.
Map on left from map on right from

12. Island Biogeography Theory
Why does the immigration rate decline as a function of S?
Immigration rate
(e.g., new species
per yr)
Why does the immigration rate decline as a function of S?
See pg. 21 MacArthur & Wilson (1967)
For a given island, notice that the immigration rate must be zero at Smax (the total number of species in the mainland species pool).
Number of species (S)

13. Island Biogeography Theory
Why does the extinction rate increase as a function of S?
Why does the extinction rate increase as a function of S?
See pg. 22 MacArthur & Wilson (1967)
For a given island, notice that there can be no extinctions when the number of species on the island is zero.
Extinction rate (e.g., number of species per yr)
Number of species (S)

14. Island Biogeography Theory
Immigration rate
(e.g., new species
per yr)
Turn-over rate (T)
Notice that turn-over rate expressly quantifies dynamism, even at equilibrium for S.
Extinction rate (e.g., number of species per yr)
Equilibrium S
Number of species (S)

15. Island Biogeography Theory
Why does the probability of immigration for each
species vary with island isolation?
Near island
Immigration rate
(e.g., new species
per yr)
Far island
TNear
TFar
Extinction rate (e.g., number of species per yr)
SFar
SNear
Number of species (S)

16. Island Biogeography Theory
Why does the probability of extinction for each
species vary with island size?
Small island
Immigration rate
(e.g., new species
per yr)
Large island
TSmall
TLarge
Note that for a given number of species already on the islands (i.e., the same number on each island), the probability that one species goes extinct is greater on a small island than on a large island.
Extinction rate (e.g., number of species per yr)
SSmall
SLarge
Number of species (S)

17. Island Biogeography Theory
Near island
Small island
Immigration rate
(e.g., new species
per yr)
Far island
Large island
Extinction rate (e.g., number of species per yr)
SFar,Small
SNear,Large
SNear,Small SFar,Large
Number of species (S)

18. Single Large or Several Small (SLOSS) Debate Ecological Assembly Rules
E.g., Sometimes we find nested subsets in which larger areas contain the same subset of species as smaller areas, plus additional area-sensitive species
Jared Diamond (b. 1937)
It’s relatively straightforward in the IBT framework to compare two islands or patches, but how does one compare one large island or patch with several small islands or patches? What about even more complicated comparisons?
From from Wikipedia

19. Single Large or Several Small (SLOSS) Debate
Nested Subsets
A B
A B C D E
A B C
Jared Diamond (b. 1937)
It’s relatively straightforward in the IBT framework to compare two islands or patches, but how does one compare one large island or patch with several small islands or patches? What about even more complicated comparisons?
In the cartoon in the slide, if the largest patch were fragmented into patches like the two smallest patches, species D & E would be lost – that’s what Diamond meant by “relaxation.”
Relaxation – loss of species that occurs after fragmentation event
If fragments contain nested subsets of species, then a single large reserve is better than several small ones of the same total area (SLOSS debate)
From from Wikipedia

20. Species Especially Vulnerable to Fragmentation
Wide-ranging
Poor dispersal abilities
Specialized requirements
Low fecundity
Vulnerable to human exploitation or persecution
Arctic tern
Cougar
Desert pup fish
Ground nut
Heliconius erato
Coyote
Images from Wikipedia

21. Lago Guri Islands, Venezuela
Not just relaxation, but devastating ecological meltdown
owing to top-down trophic cascades
Perturbation that propagates downward through two or more trophic levels, resulting in alternating positive and negative impacts on successive levels
See Case Study 7.3 in your textbook.
Top carnivores are often especially area-sensitive, so are often among the first to be lost from fragmented landscapes.
John Terborgh (b. 1936)
Photo from

22. Top-Down Trophic Cascades– + + + – + – +
Solid arrows = direct effects; dashed arrows = indirect effects
Tree seedlings
Tree seedlings
Photos from Wikipedia

23. Biological Dynamics of Forest Fragments Project (BDFFP), Amazonas, Brazil
Inaugural BBVA Foundation Frontiers of Knowledge Award in Ecology and Conservation Biology recipients in 2009.
T. Lovejoy was one of G. E. Hutchison’s last Ph.D. students (see N. Slack biography of Hutchinson).
Thomas Lovejoy
Bill Laurance
Recipients of the 2009 BBVA Foundation Frontiers of Knowledge
Award in Ecology & Conservation Biology
Photos from

24. Biological Dynamics of Forest Fragments Project (BDFFP), Amazonas, Brazil
Photo of a forest fragment, surrounded by newly created cattle pasture in Brazil

25. Biological Dynamics of Forest Fragments Project (BDFFP), Amazonas, Brazil
NASA false-color remotely sensed image of the confluence of Río Negro & Río Solimões (Amazon)

26. Biological Dynamics of Forest Fragments Project (BDFFP), Amazonas, Brazil
NASA false-color remotely sensed image of BDFFP

27. Biological Dynamics of Forest Fragments Project (BDFFP), Amazonas, Brazil
Edge effects – negative effects of a habitat edge on interior conditions
Some species can only inhabit the interior or core, and some are specifically attracted to the edge
Here, we used a strategic, stratified set of 40 of the BDFFP’s 66 1-ha study plots…
Laurance, William F., Henrique E. M. Nascimento, Susan G. Laurance, Ana Andrade, José E. L. S. Ribeiro, Juan Pablo Giraldo, Thomas E. Lovejoy, Richard Condit, Jerome Chave, Kyle E. Harms & Sammya D’Angelo Rapid decay of tree-community composition in Amazonian forest fragments. Proceedings of the National Academy of Sciences 103:
Figure from Laurance et al. (2006) PNAS 27

28. Corridors can help connect fragments
E.g., United Nations Educational, Scientific & Cultural Organization (UNESCO) World Heritage Sites in the Wet Tropics of Queensland, Australia
Map from

29. Conservation Biologists (and managers) must understand natural processes, to determine conservation targets
& how to achieve them
An example general recommendation by one NGO.
Image from

30. Conservation Biologists (and managers) must understand natural processes, to determine conservation targets
& how to achieve them
An example general recommendation by one NGO.
Image from