Transcript 1091-Lec13(corridorsP)

Shen et al. 2008
Proposed conservation
landscape for Giant Pandas in
the Mishan Mtns. China
Cons Biol 22:1144-53
Core Habitat
CH 1,3,5,6,8
25% chance of
extinction in
100yrs
Recommend
CORRIDORS
PL1 -4
OUTLINE
Corridors as a conservation tool
benefits
costs
recent evidence
large scale examples
MOVEMENT CORRIDORS: CONSERVATION
BARGAINS OR POOR INVESTMENTS?
Simberloff et al 1992 Conservation Biology 493-504
“a wildlife corridor is a linear landscape
element which serves as a linkage
between historically connected habitat,
and is meant to facilitate movement
between these natural areas”
McEuan 1993
Benefits of corridors
1962- species-area relations
Corridors increase area
linking reserves should increase species richness
1974 - equilibrium theory of island biogeography
Corridors increase immigration
Equilibrium number of species should increase
Corridors may aid dispersal,
allow recolonization or rescue of populations,
increase genetic diversity, prevent inbreeding
reduce stochastic effects
---> general recommendation for reserve design
Benefits of corridors
Beier 1993,1995 - cougars in southern California
150km2
Hwy
75km2
Santa Ana mountains 2070 km2 - 20 adults
Beier 1993, 1995
Radiocollared cougars
Movement paths
use riparian corridors
Mortality
around housing developments
roads
Models found
- cougars will not persist in the small patches
- population in large patch will not persist
without immigration from Palomar Range
Concluded
A CORRIDOR IS ESSENTIAL
Benefits of corridors
Maintain pathways for migratory species
Eg quetzals in Costa Rica
Protected breeding habitat
Monteverde Reserve
Proposed corridors
Low elevation habitat used
during non-breeding season
Benefits of corridors
Maintain connectivity for ecological processeses
Eg pollination by bees (Rudbeckia) and butterflies (Lantana)
SOURCE
Source pollen dusted with dayglo powder
Townsend and Levey 2005 Ecol 86: 466-75
Benefits of corridors
1 Aid dispersal
2. Allows migration
3 Maintains ecological processes
4. Allows range shifts due to climate change
5. Provision of escape routes from fire
6. Opportunity to avoid predation
Simberloff (1992): much cited paper
MOVEMENT CORRIDORS:
CONSERVATION BARGAINS OR POOR INVESTMENTS?
Data on corridor use is limited/
experiments are not rigorous
Data on consequences of corridors for
demography and genetic structure is
sparse
Costs of corridors may be better spent on
making larger reserves -
Hazards of corridors
1. Corridors may provide avenue for catastrophes
(predators, fire, disease)
corridors may attract edge-inhabiting predators
isolated reserves quarantine disease
2 Corridors may act as entry route for exotics
corridors may favour movement of introduced spp
corridors may be reservoir for weeds
3. Corridors may function as sinks
4. Corridors with no buffer zone may expose
migrants to danger
Exposure to domestic animals, roads, etc
5. Corridors may facilitate poaching/trapping
Corridors: a philosophical slant
Corridors are easily understood.
Is it good conservation practise to sell
the easiest program in the absence of
evidence it is the most effective?
Is it beneficial for people to feel that
they are doing something important
for conservation in the absence of
evidence they are doing anything
17 years after Simberloff
Do corridors provide connectivity?
Approaches
do animals/plants use corridors
do corridors influence demography
do corridors influence genetic structure
do corridors influence diversity
do animals/plants use corridors?
Experimental corridors in S Carolina
Corridors promote movement in diverse taxa
do animals/plants use corridors?
Experimental corridors in S Carolina
Obs
Birds usually fly parallel to edge
Model
Predict bird and seed movement in
connected/unconnected patches
Expt
Feed birds-track seeds of wax myrtle
do corridors influence demography?
Control corridor fragment
5700 individuals
22600 captures
Survival
higher in corridor linked grids
Population size less variable in corridor linked grids
Coffman et al 2001 Oikos 93: 3-21
do corridors influence demography?
Mountain pygmy possum
Contiguous Fragmented by ski development
Females winter
at higher
elevation
Males move to
lower
elevations
Males can’t move
--> lower female survival
and skewed sex ratio
+ TUNNEL
normal sex ratio and survival
do corridors influence genetic structure?
Red squirrels
Deforestation in 19th century -->
Dwindling poplations in small isolated patches
Populations become genetically distinct
Reforestation 1950’s --->
Kielder forest
links some populations
Genetic data - 1920’s museum skins
- 2001 resampled populations
do corridors influence genetic structure?
Red squirrels
Fragmented
Linked by stepping stone corridor
Reforestation has allowed genetic mixing of
Scottish and Cumbrian populations
do corridors influence species diversity?
Gilbert et al. 1998 ProcRSoc 265: 577-82
Moss micro-arthropod communities on rocks
What is predicted?
do corridors influence species diversity?
Gilbert et al. 1998 ProcRSoc 265: 577-82
Moss micro-arthropod communities on rocks
What is predicted?
Corridors and connectivity
Diverse taxa do use corridors
- reasonable evidence
Corridors can influence demography
- some evidence
Corridors can influence genetic processes
- some evidence
Corridors can influence diversity
- some evidence
Despite criticisms
Corridors may be best solution to a complex
problem
Conservation corridors
Example 1. The Terai Arc
250 bengal tigers
11 protected areas
Conservation corridors
Example 1. The Terai Arc
WWF+ partners
Goal - link the 11 protected areas
Khata corridor - 3 km long
Links Royal Bardia to Kataniaghat
2001 - restoration commenced
community forests and
plantations
2004 - Elephant and tiger using
corridor
250 bengal tigers
Conservation corridors
Example 2. The Mesoamerican corridor
Wildlife Conservation Society initiative
7 countries
Chiapas, Mexico to
Darrien Gap, Panama
1996 GIS model linking
reserves, remaining forest
Progress slow
Costa Rica 39
Mexico/Belize 4
Corridors- unresolved questions
Which spp use corridors? Which benefit
How do residency and movement rates
differ among taxa
“passage” vs “corridor dwellers”
How does utilization change with shape,
width, length, landscape?
Will corridors promote the movement of
exotics and disease?
Gibert ert al. 1998 Corridors maintain species richness in the fragmented landscapes of
a microecosystem. P Roy Soc Lond B 265: 577-582
Damschen, EI et al. 2006 Corridors increase plant species richness at large scales
SCIENCE 313: 1284-6
Shepherd, B and Whittington, J 2006. Response of wolves to corridor restoration and
human use management ECOLOGY AND SOCIETY 11
Dixon, JD et al. 2006. Effectiveness of a regional corridor in connecting two Florida black
bear populations CONSERVATION BIOLOGY 20: 155-162
Martensen et al. 2008. Relative effects of fragment size and connectivity on bird
community ib the Atlantic Rainforest BIOLOGICAL CONSERVATION 141: 2184-92
Lees AC and Peres CA 2008 Conservation value of remnant riparian corridors of varying
quality for Amazonian birds and mammals Conservation Biology 22 439-449
Beier P et al. 2008 Forks in the road: choices in procedures for designing wildland
linkages. CONSERVATION BIOLOGY 22: 836-51
Points for discussion
Corridors - are benefits taxon specific
- how can we examine costs
- what do we want them to do
- how do we design them