Fragmentation and Fragmentation and Management of Management of

Landscape Landscape

How many red spots How many red spots make a white cow red? make a white cow red?

How many clearing How many clearing make a forest, prairie? make a forest, prairie?

A threshold reached?A threshold reached?

(Forman and Godron 1986)(Forman and Godron 1986)

Where was it from? Where was it from? Origins & Definitions Origins & Definitions

Where we are? Where we are? Problems – Case Studies Problems – Case Studies Importance of Importance of

fragmentation.fragmentation. Where to go? Where to go?

Achievements & Achievements & Necessities Necessities

Island Biogeographic Island Biogeographic Theory Theory

Early interest in habitat fragmentation Early interest in habitat fragmentation arose from island biogeographic theory arose from island biogeographic theory (MacArthur and Wilson, 1963 & 1967).(MacArthur and Wilson, 1963 & 1967).

(MacArthur and Wilson, 1963)

19.4 – fish 198219.4 – fish 1982

(Preston, 1962; Nilsson et al. 1988)

19.3 – mammal 198919.3 – mammal 1989

The equilibrium The equilibrium model of island model of island biogeography by biogeography by MacArthur and MacArthur and Wilson (1963)Wilson (1963)

DefinitionsDefinitions Broad DefinitionBroad Definition: transformation

of original continuous forest landscape into small and isolated remnant patches of plantation or non-forest habitat. It is simply the disruption of continuity.

Narrow DefinitionNarrow Definition: Breaking up of a habitat or land type into smaller parcels

Examples – FragmentationExamples – Fragmentation

NE China

MiomboAfrica

Bayfield(WI)

MarabaAfrica

Fragmentation: Habitat LossFragmentation: Habitat Loss

(1986) (1993) (1999)

Rondonia, Brazil

Fragmentation: Subdivision of Fragmentation: Subdivision of habitathabitat

From Dar Roberts, CA

Fragmentation: Patch IsolationFragmentation: Patch IsolationObserved reproductive rates were low enough for some species in the most fragmented landscapes to suggest that their populations are sinks…. Conservation strategies should consider preservation and restoration of large, un-fragmented “core” areas in each region.

FragmentationFragmentation: Edge Effects: Edge Effects

1972

2001

The forested areas of Warwickshire, England (shown in black) (Wilcove et al. 1986)

1km

1km

50 m

81 ha

69 ha

59 ha

30 m

The Checkerboard The Checkerboard LandscapeLandscapePatterns of

clearcutting development under various models(a-c) Progression of clearcutting using the dispersed patch model in which areas are selected for cutting so as to be distributed regularly across the landscape: shown are 25, 50, and 75% cutover points. (e-f) Pattern of cutting at 50% point using single, four nucleus, and aggressive-parallel cutting systems. (Franklin & Forman 1987)

Susceptibility of forests in the Douglas-fir region to various damaging agent along a landscape cutting gradient as shown by the checkerborad model. (Franklin & Froman 1987)

Landscape structurePatch densityPatch sizeInter-patch distanceConnectivityBoundary lengthInterior/edge ratioMaximum of core (interior forest)Total interiorStepping stonesCorridors

SpeciesIsolationNumber of generalistExotic speciesNest predationExtinction rateDispersal of interior speciesLarge-home-range speciesRichness of interior species

OthersMetapopulation dynamicsGenetic inbreedingSize of disturbance patchesCumulative effects (rain, snow and flooding effects)

EFFECTS OF FRAGMENTATION

Creating Land Mosaics

An old-growth patch surrounded by a long rotation island that is cut in a programmed sequence such. ( Harris 1984)

ConclusionsConclusions

The number, size, and arrangement of the patches in a mosaic created by forest managers strongly influence the degree to which management objectives are fulfilled.

Two recommendations are: (1) reduce the emphasis on dispersing small clearcut patches through the forest landscape, and (2) identify and reserve large patches of primeval forest in the landscape for maintenances of interior and amenity values.

SLOSS debate

What do we want to know about What do we want to know about fragmentation? fragmentation?

What are the relationships among patch area, patch shape, What are the relationships among patch area, patch shape, patch isolation, edge, the interaction of these factors, and patch isolation, edge, the interaction of these factors, and various population and ecosystem? various population and ecosystem?

How do various landscape elements, such as corridors, linear How do various landscape elements, such as corridors, linear networks, and matrix, affect various ecosystem processes and networks, and matrix, affect various ecosystem processes and the connectivity of populations in fragmented landscapes? the connectivity of populations in fragmented landscapes?

How do pattern-process linkages function in spatially and How do pattern-process linkages function in spatially and temporally dynamic landscapes across the range of spatial temporally dynamic landscapes across the range of spatial and temporal scales? and temporal scales?

What levels of habitat loss and fragmentation does population What levels of habitat loss and fragmentation does population viability decline drastically? viability decline drastically?

How long does it take population and ecosystem processes to How long does it take population and ecosystem processes to respond to physical changes in the landscape associated with respond to physical changes in the landscape associated with fragmentation? fragmentation?

Manipulative and Mensurative Manipulative and Mensurative Experiment - Two Major ApproachesExperiment - Two Major Approaches Manipulative experiment Manipulative experiment

Physically manipulates some attribute of Physically manipulates some attribute of the system in a controlled manner, while the system in a controlled manner, while holding all other attributes constant. holding all other attributes constant.

Mensurative experimentMensurative experiment Simply observes or measures the system Simply observes or measures the system

at different locations or times at different locations or times The treatment is the different conditions The treatment is the different conditions

in space or time. in space or time.

Generally, manipulative experiments lead Generally, manipulative experiments lead to stronger inferences and therefore more to stronger inferences and therefore more reliable knowledge than mensurative reliable knowledge than mensurative experiments.experiments.

A Ideal Manipulative experiment requires A Ideal Manipulative experiment requires The similarity among landscape minimizes the The similarity among landscape minimizes the

experimental errorexperimental error The size of the landscape are functionally The size of the landscape are functionally

relevant to the process/organism(s) under relevant to the process/organism(s) under considerationconsideration

Areal extent and configuration manipulation is Areal extent and configuration manipulation is needed to assess independent and interactive needed to assess independent and interactive of processes of processes

Replication and RandomReplication and Random Temporal and Spatial Controls (Natural Temporal and Spatial Controls (Natural

Variability)Variability) Observing the delayed effect Observing the delayed effect

Mensurative ExperimentMensurative Experiment Can overcome some of the important Can overcome some of the important

limitations limitations The practical and logistical difficulties of The practical and logistical difficulties of

implementing large-scale treatment implementing large-scale treatment No practical limit to the spatial or temporal No practical limit to the spatial or temporal

scale of the study system scale of the study system Flexibility in time lag effect Flexibility in time lag effect

Still problems … Still problems … Additional sources of variation associated Additional sources of variation associated

with inconsistent and uncontrolled past with inconsistent and uncontrolled past perturbations perturbations

Lack in pretreatment control – owing to Lack in pretreatment control – owing to substituting space for time – inherent substituting space for time – inherent variability and autocorrelation variability and autocorrelation

Landscape level studyLandscape level study Isolation of a process Isolation of a process Extinction threshold/ Time lag/ Extinction threshold/ Time lag/

synergisms between habitat area synergisms between habitat area and configuration and configuration

Inequity in the organismal focus Inequity in the organismal focus Invertebrates, reptiles, and amphibians Invertebrates, reptiles, and amphibians

Replication / Poorly controlled Replication / Poorly controlled Spatial information Spatial information

Lack in …Lack in …