Shen et al. 2008 Proposed conservation landscape for Giant Pandas in the Mishan Mtns. China Cons Biol 22:1144-53

Core Habitat CH 1,3,5,6,825% chance of extinction in 100yrs

RecommendCORRIDORS PL1 -4

OUTLINE

Corridors as a conservation tool

benefitscostsrecent evidencelarge 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 relationsCorridors increase arealinking reserves should increase species richness1974 - equilibrium theory of island biogeographyCorridors increase immigrationEquilibrium number of species should increase Corridors may aid dispersal, allow recolonization or rescue of populations, increase genetic diversity, prevent inbreedingreduce stochastic effects ---> general recommendation for reserve design

Benefits of corridors

Beier 1993,1995 - cougars in southern California

Hwy

75km2

150km2

Santa Ana mountains 2070 km2 - 20 adults

Beier 1993, 1995

Radiocollared cougarsMovement paths

use riparian corridorsMortality

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 habitatMonteverde Reserve

Low elevation habitat used

during non-breeding season

Proposed corridors

Benefits of corridors

Maintain connectivity for ecological processeses

Eg pollination by bees (Rudbeckia) and butterflies (Lantana)

SOURCE

Source pollen dusted with dayglo powderTownsend and Levey 2005 Ecol 86: 466-75

Benefits of corridors

1 Aid dispersal2. Allows migration3 Maintains ecological processes

4. Allows range shifts due to climate change5. Provision of escape routes from fire6. 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 predatorsisolated 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 sinks4. Corridors with no buffer zone may expose

migrants to dangerExposure 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 SimberloffDo corridors provide connectivity?

Approachesdo animals/plants use corridorsdo corridors influence demographydo corridors influence genetic structuredo 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

ObsBirds usually fly parallel to edgeModel Predict bird and seed movement in connected/unconnected patchesExptFeed birds-track seeds of wax

myrtle

do corridors influence demography?

Control corridor fragment

5700 individuals22600 captures

Survival higher in corridor linked gridsPopulation 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 Males can’t move

--> lower female survivaland skewed sex ratio

+ TUNNEL

normal sex ratio and survival

Females winter at higher elevation Males move to lower elevations

do corridors influence genetic structure?

Red squirrelsDeforestation in 19th century -->

Dwindling poplations in small isolated patchesPopulations 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 squirrelsFragmented 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 rocksWhat is predicted?

do corridors influence species diversity?

Gilbert et al. 1998 ProcRSoc 265: 577-82

Moss micro-arthropod communities on rocksWhat 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 criticismsCorridors may be best solution to a complex problem

Conservation corridors

Example 1. The Terai Arc

11 protected areas

250 bengal tigers

Conservation corridors

Example 1. The Terai Arc

WWF+ partners Goal - link the 11 protected areasKhata corridor - 3 km longLinks Royal Bardia to Kataniaghat2001 - restoration commenced

community forests and plantations2004 - Elephant and tiger using corridor

250 bengal tigers

Conservation corridorsExample 2. The Mesoamerican corridor

Wildlife Conservation Society initiative

7 countriesChiapas, Mexico toDarrien Gap, Panama

1996 GIS model linking reserves, remaining forest

Progress slowCosta Rica 39Mexico/Belize 4

Corridors- unresolved questions

Which spp use corridors? Which benefitHow 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 scalesSCIENCE 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