Kevin McGarigalBrad Compton

andScott Jackson

Critical Linkages

Assessing Local and Regional

Landscape Connectivity for

Transportation Planning in

Massachusetts

http://www.umasscaps.org

Conservation Assessment & Prioritization

System (CAPS)

Landscape Ecology Lab

Assessing ecological integrity and

supporting decision-making for

land conservation, habitat

management, project review &

permitting to protect biodiversity

Ecological Community

Approach

GIS data

Land cover

map

Integrity

metrics

Index of Ecological

Integrity

The CAPS Analysis

Integrated Index of

Ecological Integrity (IEI)

CAPS Critical Linkages ConceptsThe Three Faces of Connectivity

Dispersion

Connectedness

Conductance A B

Ecological Setting

…refers to the principal physical and chemical characteristics

at multiple scales that strongly influence the composition,

structure and function of a particular point in the landscape

over the long term and serve to describe and distinguish it

ecologically.

• Includes both local environmental conditions and

landscape context

• Relatively static at relevant ecological time frames

• Ecological conditions may vary in response to natural and

anthropogenic disturbances

Flo

w g

rad

ien

t

Hydroperiod

Ecological Setting

Flo

w g

rad

ien

t

Hydroperiod

Ecological Setting

Ponds

Forested Wetlands

Intermittent

Streams

Riverine

Marshes

Fringe Buttonbush Swamps

Aquatic Bed

Backwaters

Vernal Pools

Ecological Setting Variables

Temperature

• Growing season degree-days

• Minimum winter temperature

Solar energy

• Incident solar radiation

Moisture

• Wetness/Soil moisture

Hydrology

• Flow gradient

• Flow volume

•Tidal regime

Physical Disturbance

• Wind exposure

• Wave exposure

• Steep slopes

Chemical & physical substrate

• Soil pH

• Soil depth

• Soil texture

• Substrate mobility

• Water salinity

• Water CaCO3 content

Vegetation

• Vegetative structure

Development

• Developed

• Traffic rate

• Impervious

•Aquatic barriers

• Terrestrial barriers

Ecological Setting

Su

bstr

ate

Physical Disturbance

• Temperature

• Solar energy

• Substrate

• Physical disturbance

• Moisture

• Hydrology

• Vegetation

• Development

Similarity Matrix

(26 Variables)

Cell #1: ForestResistant Surface

Cell #2: ForestResistant Surface

Cell #3: Forested WetlandResistant Surface

Cell #4: RiverResistant Surface

Land Cover

Cell #1: ForestResistant Surface

Resistant Kernel

Cell #2: ForestResistant Surface

Resistant Kernel

Cell #3: Forested WetlandResistant Surface

Resistant Kernel

Cell #4: RiverResistant Surface

Resistant Kernel

Connectedness

Aquatic Connectedness

Critical LinkagesPhase I

Landscape Ecology ProgramDepartment of Environmental Conservation University of Massachusetts, Amherst

Critical Linkages Phase I

Beforecell 1

Aftercell 1

∆-Connectedness for Roads

Δ-Aquatic Connectedness

Critical Linkages Results: Crossings

Critical Linkages Results: Dams

Critical Linkages II

Assesses the effect of landscape changes on regional connectivity.

o Over a regional scale, concerned with connecting important conservation areas (“nodes”).

o Terrestrial connectedness only, because there are multiple choices when moving over land, but only one path when moving through stream network.

Definitions

NodeAn area of conservation interest (a.k.a. reserve). Critical Linkages II focuses on connections among nodes.

Contingent unitA specific place in the landscape that may change.

a. For road passage analysis, contingent units are sections of highway where road passage structures may be built.

b. For development analysis, contingent units are parcels of land that may be developed.

Node 1

Units

Node 2

A

B

C

Node 2

Random Low-Cost PathA possible route between a pair of nodes. Somewhere between the least-cost path (the single optimal route) and a random walk (which never really gets anywhere).

Node 1

Path distanceThe total length of a path in terms of functional distance: the sum of landscape resistance for each cell the path traverses.

Path distance may be assessed in terms of functional distance (resistance) or in terms of P(connect), given a bandwidth, based on dispersal ability.

distance = 8477P(connect) = 0.72

Node 2

Node 1

0 1

distance ÷ bandwidth

P

0

1

2 3 4

Mean functional distance = 9268 m

Mean P(connect) = 0.61

Internode distanceThe distance between a pair of nodes is simply the mean of all path distances between the nodes.

Node 2

Node 1

Probability of Connectivity (PC)Saura and Pascual-Hortal (2007)

A metric of the total landscape connectivity among nodes (each with a size or value) given P(connect) among nodes.

An unfragmented landscape consisting of a single giant node has PC = 1.

A landscape with few small, disconnected nodes approaches PC = 0.

∆PC

The change in probability of connectivity for a landscape after changing the size of nodes or P(connect) among nodes.

Changes that increase connectivity get a positive ∆PC.

Changes that decrease connectivity get a negative ∆PC.

Node 1

Node 2

C

A

B

Identify nodes and contingent units.

1. The Analysis

Calculate PC for the current landscape.

PC = 0.694

2.

Node 1

Node 2

C

A

B

Build lots of random low cost paths between each pair of nodes. Note which units are crossed by each path.

3.

Node 1

Node 2

Conductance Index

Sum of random low cost paths crossing through a particular cell gives the conductance index.

4.

Node 1

Node 2

C

A

BEvaluating links:

Select each unit, one at a time, and build a wildlife passage, thus changing the path distance for all paths that traverse the unit.

Recalculate PC and get ∆PC for the current unit.

5.

PC = 0.694 PC = 0.721

∆PC = 0.027

6.

Map the best single links across the landscape.

Nodes

• BioMap2 Candidate Forest Cores

• BioMap2 Candidate Wetland Cores

• Lentic portions of BioMap2 Aquatic Cores

• BioMap2 Vernal Pool Complexes

• Protected Open Space with IEI > 0.7

• Size threshold of 200 ha

Random Low-Cost Paths

Forest Forested Wetland Shrub Swamp Wetland

Random Low-Cost

Paths

Conductance index

Conductance Index

2k5k

10k

Conductance Index

Node Importance

Link Importance

Nodes

Conductance Index

Contingent Units

Contingent units: Road segments

(traffic ≥ 500 vehicles/day)

Critical Linkages

20 Most Important Linkages

20 Most Important Linkages

http://www.umasscaps.org

Funding and Other Support Provided by:

The Nature Conservancy

Federal Highway Administration

MA Department of Transportation

MA Department of Environmental Protection

MA Natural Heritage & Endangered Species Program

MA Office of Energy & Environmental Affairs

US Environmental Protection Agency

The Trustees of Reservations

Massachusetts Audubon Society

USDA’s Cooperative State Research, Education, and Extension Service (CSREES) is our federal partner, providing federal assistance and

program leadership for numerous research, education, and extension activities.