Transcript Species, Area, & the Equilibrium Theory of Island Biogeography

Species, Area,
& the Equilibrium Theory of
Island Biogeography
as a foundation paradigm
in conservation biology
Part 2…
Preserve Design Guidelines
IBT & Design
•
•
•
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A. Large is better than small
B. Undivided is better than divided
C. If divided, close is better than far
D. If divided, distances should be
equal
• E. Corridors are better than no
corridors
• F. Circular is better than narrow (low
perimeter to area ratio)
Size
Better
Worse
Fragmentation
Better
Worse
Distance
Better
Worse
Clustered
Better
Worse
Connectivity
Better
Worse
Shape
Better
Worse
IBT & Design
The
SLOSS Debate
Single Large
Or
Several Small
of the same total area
Several Small > Single Large
Florida scrub vertebrates--McCoy &
Mushinsky 1994
Butterflies, Spain--Baz & Garcia-Boyera 1996
Plants, Norway--Saetersdal 1994
Plants in mires, Finland--Virolainen et al. 1998
Birds--Loman & von Schantz 1991
Sequoia-Kings Canyon NP vs. CA State Parks -- Species
Richness
From Stohlgren & Quinn 1993
SEKI CA State Parks
4000
Area
Area and Number of Species
3500
3341
3000
Plants
2500
1951
2000
1485
1500
1402
Birds
1000
434
500
195
0
1
2
Comparision
3
Megareserves for large predators
>106 ha
100 km linear extent
Simberloff & Abele 1976
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•
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•
Island A becomes Archipelago A
Island B becomes Archipelago B
For A, SS > SL
For B, SL > SS
Simberloff & Abele 1976
Area m2
Spp
A
475
77
-------------------------------A1
119
51
A2
133
48
A3
80
47
A4
102
50
Archipelago A
434
81
81 > 77!!
Simberloff & Abele 1976
Area m2
Spp
B
168
56
-------------------------------B1
71
36
B2
87
32
Archipelago B
158
47
47 < 56!!
Immediate Complaints
Diamond, Terborgh, Whitcomb
• Not all spp equal
– Some extinction prone, Total Spp not the
best measure of success
– Large predators need 100s-1000s km2
– Colonial nesters, Migrating spp, Spp
dependent on core
• Small reserves loose the same Spp, so
become more similar to each other,
more overlap, Spp lists are nested
SLOSS?? It depends!
Several Small
Species overlap (similarity) among islands
Simberloff & Abele 1972
• The Diamond Isles
• The Lack Archipelago
• The Tallahassee Archipelago
Scale dependence
CONSERVATION STRATEGY
Both grain and extent are critical!
Grain: Ecological integrity, Population viability
Hydrology, Black bears, Vagile species
Extent: variation in environment and history
Local endemics, Poorly dispersed species
Representativeness
SLOSS is here to stay because grain &
extent maximize different contributions to
biodiversity
The Umbrella Concept
Protecting large animals that require large
areas & play important ecosystem roles
--large bird & mammalian predators—
protects all species
Does the Umbrella Species Idea Work?
Carnivore plan would protect 43%
of North American invertebrates
No better than random placement
Kerr 1997
Plants > birds as the umbrella group
for other taxa, S California
Ryti 1992
Vertebrates missed lower plant diversity
Portugal
Araujo 1999
Rare species captured common species;
Common species did not capture rare
Rebelo & Siegfried 1992
Other island-like models
• Gene flow
• Metapopulations
• Landscape ecology
Other SLOSS-like debates
• GLOSS: Is it better to sample genes
from one population or from several
small populations of the same total
size (number of individuals sampled)?
• SLOPP: Is it better to protect one
large population or several small
populations of the same total size?
• FLOSS: Is it better to introduce a
species as one large release or
several small releases?
Conservation as sampling
• By definition we conserve a subset of
the original
• What is the best conservation
sample?
• What are the consequences of
fragmentation?
• Thing and process
The Two Triangles
The Constraint of Size
A continuum of area sensitivity
Starting with large predators, 106 ha
Headwaters of streams
Disturbance regimes, pattern and process
Dependence on multiple habitats; seasonal movements
Exceptions: rare species dependent on rare habitat;
air pollution; alien invasions; climate synchronization;
long distance migration
Size: completeness, wholeness, integrity, health
Costs of management and conservation success
Conservation as sampling: bigger areas are better samples
Feasible restoration goals depend on size
BUT any site can play a role…dependent on size
The Two Triangles Continued
Small areas
Small area requiring species, habitats
Connectors, stepping stones
Representation: more places
Air, Water, Soil quality
Environment: temperature
Human-nature connections
Human well-being