Habitat Loss and Fragmentation - TVHS APEStvhsapes.weebly.com/uploads/7/5/9/5/75954777/habitat_loss.pdf · 3 3 basic landscape elements Patch – recognizable area that contrasts

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Habitat Loss and Fragmentation

Originally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum

Fuente: Center for Biodiversity and Conservation

What is:“Habitat Fragmentation” ?

The end result of human settlement and resource extraction in a landscape is a patchwork of small, isolated natural areas in a sea of developed land…

Gascon et al. 1999


Created by John Rozum, NEMO National Coordinator

Habitat fragmentation can also be thought of as “a disruption of continuity”

Source: Department of Landscape Architecture & Environmental Planning Utah State University


Example: Forest Fragmentation

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Example: Wetland Fragmentation

Source: New York State GIS Clearinghouse


Example:PrairieFragmentation

Source: J.S. Aber


Short-grass prairie has been reduced to < 0.1% of its former extent

Landscapes

What is a landscape?

An area that is heterogeneousA mosaic where a mix of local ecosystems and land uses is repeated over space

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3 basic landscape elements

Patch – recognizable area that contrasts with adjacent areas and has definable boundaries

Corridor –connects two or more patches

Matrix – the “background” or dominate cover type upon which patches and corridors occur

Patch

Matrix

Corridor

Small bird

How large is a landscape?

Landscape for an ant

What started us thinking about certain landscape elements, like

patch size?

Does it apply to habitat fragmentation?

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fragmentation reduces area and increases

isolationWildlife communities in small woodlots are

• less diverse

• less abundant

Island biogeography applied to habitat fragmentation

Wildlife communities in large forested areas:

• more diverse

• more abundant

Island biogeography and habitat fragmentation Habitat loss vs. fragmentation

Habitat loss – results in less habitat for focal species or group

Fragmentation – technically, the breaking apart of habitat (not always with net loss)

Habitat loss

Habitat fragmentation

…but they both usually occur together

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The Fragmentation Process


Landscapes are fragmented in a fairly predictable fashion

Source: Gibbs et al. 1998


Perforation - Holes punched in a habitatDissection - Initial sub-division of continuous landscape Fragmentation - Breaking up into smaller partsShrinkage - Reduction in size of patchesAttrition - Loss of patches

Image source: Mark C. Wallace

Technical Terms for the Fragmentation Process


Created by John Rozum, NEMO National Coordinator

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Example of the Forest Fragmentation Process

Source: http://www.cr.usgs.gov/earthshots/slow/Rondonia/Rondonia

Moist Forest, Rondonia, Brazil 1975 - 1992


Another Example

Temperate Hardwood Forest, Cadiz Township, Wisconsin, USA


Forests, Warwickshire, England, Last 2000 yrs

Left: South-east Asian Tropical Deforestation is particularly severe, despite the region being the second only to the Amazon for biological diversity: (a) India, Sri Lanka Almost all primary rainforest destroyed. (b) Thailand 45% loss between 1961 and 1985. Will lose 60% by 2000. (c) Malaysia Forest resources exhausted by 2000. (d) Indonesia 620,000 hectares / year.

(e) Philippines 55% forest loss 1960 - 1985. (f) Bangladesh All primary rainforest destroyed (Lean 67). Right: Sumatra deforestation. (Groombridge)

Differences between Natural and Anthropogenic Habitat Fragmentation


But are natural environments not already fragmented?


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What then are the differences between human-caused fragmentation and natural “patchiness”?

(1) A naturally patchy landscape has a complex patch structure, whereas one fragmented by humans has simplified patches.


Missouri's Big Oak State Park

(2) Many (but not all) of the patch types in human modified landscapes are not suitable for wild life.

Faunal data from Amazon Birds: 123 species

31 use matrix 92 that use forest edge or interior (none restricted to the forest interior)

Frogs; 62 species16 use only the matrix1 only in forest interior51 in forest edge and interior.

Mammals: 15 species4 use the matrix only, 15 forest interior only10 use the forest edge

Ant species, 127 species32 use matrix only104 use the primary forest44 use the forest edge

(3) Because of (1) & (2) there is less contrast between adjacent patches in naturally patchy landscapes and therefore potentially less intense “edge effects.”

(4) Certain features of fragmented landscapes, such as roads, are completely novel and pose specific threats to wild species.

1900 versus 1990

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Biological Dimensions of the Fragmentation Process


Changes in the landscape…The total area of available habitat decreases,

The area of remaining habitat patches decreases,

The number of remaining habitat patches increases, and

The connectedness of remaining habitat decreases (farther apart, more hostile habitat in-between).

Examples of “area-sensitive”species: Neotropical migrant songbirds of deciduous forests of the eastern United States

Source: C. S. Robbins


Species with large area requirements

Ivory-billed woodpeckers: ca. 7 km2 per breeding pair

male mountain lion (puma): home range of 400 km2

Cerulean Warbler: 1000 ha (a circle about 3.5km in diameter)

Isolation affects MetapopulationViability – the “Connectivity” Issue


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Migration rates between patches as a Migration rates between patches as a function of distances between patchesfunction of distances between patches

00.10.20.30.40.50.60.70.80.9

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0 1000 2000 3000 4000 5000 6000

Inter-wetland distance (m)

Prob

abili

ty o

f dis

pers

ing

betw

een

wet

land

s

Amphibians

Reptiles


Mechanisms by which habitat fragmentation reduces metapopulation viability

Fragmentation reduces patch sizes and population sizes, thereby increasing extinction rates

Fragmentation increases inter-patch distance and reduces migration rates between patches, thereby reducing the likelihood of local populations sustaining one another


The Rescue Effect

Immigration from a large, productive subpopulation can keep a declining subpopulation from going extinct

Long-term effects of reduced patch area and isolation on extinction rates

From: Newmark. W.D. 1996.


Edge Effects


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Edge Effects: Depend on Patch Shape and the Types of Adjacent Patches

Area: 259 hectaresEdge: 11,771 meters

Area: 259 hectaresEdge: 6,748 meters

Source: Department of Landscape Architecture & Environmental Planning Utah State UniversityOriginally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum

Edge Effects

Microclimate changes in light/temperatureWindExoticsFireHunting pressure by humans and other predators


Fig. 2. Predation rates on artificial nests decline with distance from a forest edge. Edge-related predation extends 300_600 m into the forest (from Wilcove 1985).

Fragmentation and Ecosystem Function

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Fragmentation and Ecosystem Change


•Plots deepest in the interior of the remaining fragments showed no change in biomass.

•Those closest to the edge lost as much as 5 tons of biomass per hectare per year, a rate of about 1.3% per year.

Edge Effects: Extent


Preserving Biodiversity in Fragmented Landscapes


Analysis and Planning

1. Conduct a landscape analysis - where are the big blocks and connections?

2. Evaluate the landscape in a regional context

3. Can planning avoid further fragmentation, e.g., via corridors?

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Identifying Core Regions at the Regional Scale

Source: Ersts, Center for Biodiversity and Conservation


Evaluating fragment isolation and scoping out potential corridors

102 km

91 km 89 k

m

43 km

Source: Ersts, Center for Biodiversity and Conservation


Considering Edge and Patch Area Issues for Reserve Design

Source: Blair and Ballard 1996


Minimize negative edge effects

Do not ignore small fragments!

Invertebrates, seed sources, nuclei for restoration

Corridors?

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Butterfly Movements Through Corridors

Seed Dispersal Through Corridors Potential Advantages of CorridorsIncreased immigration rate to fragments could:

increase effective population sizes of particular species and decrease probability of extinction (provide a "rescue effect")

permit re-establishment of extinct local populations

Reduce inbreeding depression and maintain genetic variation within populations

More advantagesProvide increased foraging area for wide-ranging species

Provide predator-escape cover for movements between patches

Provide alternative refugia from large disturbances (a "fire escape")

DisadvantagesFacilitate the spread of

epidemic diseases,

insect pests,

exotic species,

weeds,

fire and other abiotic disturbances ("contagious catastrophes")

Increase exposure of wildlife to hunters, poachers, and other predators

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Example: The Effect of Implementing a Prohibition on Riparian Zone Clearing

(Source: Department of Landscape Architecture & Environmental Planning Utah State University)


Evaluating Corridors and Connectivity at the Regional Scale: The Proposed Paseo Pantera

Source: The Wildlife Conservation SocietyOriginally created by James P. Gibbs (SUNY-ESF) & Melina F. Laverty (AMNH) , Integrated Conservation Biology Curriculum Materials for Tropical Countries Project, http://research.amnh.org/biodiversity/programs/curriculum

Evaluating Corridors and Connectivity at the Regional Scale: Central Appalachian Mountains

Source: The Wildlands Project


Guideline Impact on LandscapeAvoid forest clearing within 150 m of water courses

Enhances landscape connectivity, protects water quality

Avoid clearing on steep (>30 degree) slopes

Retain forest remnants in sensitive areas, reduce flooding and erosion

Avoid clearing rare vegetation types Protect rare communities and seed sources

Keep clearings to < 20 ha, Restrict clearing of primary forest to < 50% of property ownership

Reduces loss and fragmentation

Prohibit clearing or hunting within 1 km of protected areas

Reduces edge effects

(Source: Laurance & Gascon 1997)

Specific Recommendations for Minimizing Fragmentation of Tropical Wet Forests


Recent corridor experimentation

Damschen et al. 2006. Corridors increase plant species richness at large scales. Science 313:1284-1286.

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Recent corridor experimentation

Damschen et al. 2006. Corridors increase plant species richness at large scales. Science 313:1284-1286.

Habitat Fragmentation (End)

Documents

Habitat Loss and Fragmentation - TVHS APEStvhsapes.weebly.com/uploads/7/5/9/5/75954777/habitat_loss.pdf · 3 3 basic landscape elements Patch – recognizable area that contrasts