Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 21 Landscape Ecology

What is a “Landscape” An area of the Earth’s surface that is comprised on multiple ecosystems that are connected by exchanges of organisms, matter, and energy. Multiple ecosystems can be identified based on differences in environment, species composition or stage of succession since last disturbance.

Elements of Landscapes Patch: A non-linear, area with more or less homogeneous species composition, environment, and stage of succession. Corridor: A linear patch (length much greater than width), w/ homogenous composition, that often connects one patch with another patch; facilitates migration of organisms b/t patches. Matrix: The most common type of patch in a land-scape. The environment / community- type that usually surrounds other types of patches.

Landscape Elements Patch Matrix Corridor

Delaware County Landscape What is the matrix? Forestpatch Rivercorridor I - 69 corridor

Reasons for Differences Among Patches Spatial Variation in Surface Geology –Topography Micro-Climate w/ Elevation and Slope-Aspect Drainage / Water Flow Rate –Bedrock Geology Soil / Water chemistry Soil texture Spatial Variation in Disturbance / Succession Activities of Animal Species (e.g. Beaver) Human Land-Use Patterns

Change in an American Landscape w/ Beaver Re-Introduction

Change In Dutch Landscape w/ Collapse of Sheep Herding Where the sheep were grazed

The Original Indiana Landscape

The Current Indiana Landscape Matrix changed from forest to agricultural land Interaction Between Geology and Human Land-Use: Forest patches retained only on land not suitable for agriculture. - poor drainage - topographic relief

Why Do We Care That Landscapes Look Like Patch-work Quilts ? Different kinds of landscape patches provide different habitats. Habitat Diversity Species Diversity Landscape Species Diversity –Species Diversity w/in Habitat Patches –Diversity of Different Habitat Patches

Why Do We Care That Landscapes Look Like Patch-work Quilts ? Elimination of all patches of a particular type eliminates habitat for all species that live in that patch type. Habitat Loss Species Extinctions at the at the Landscape Level Maintaining habitat diversity is the MOST important way to maintain overall diversity at large spatial scales.

Why Do We Care That Landscapes Look Like Patch-work Quilts ? Populations of species that live in widely dispersed habitat patches (Meta-populations) are at greater risk of extinction than populations of the same size that live in a single large habitat area.

Northern Spotted Owl Meta-Population Old-Growth Forest Habitat Patches

Why are Meta-Populations More Likely to Go Extinct ? Inbreeding more common in small, isolated sub-populations. –Reduced genetic variability –Reduced immune defense against disease –Increased expression of lethal recessive traits –Reduced fertility –Increased mortality

Why are Meta-Populations More Likely to Go Extinct ? Small sub-populations more likely to be completely wiped-out by a disturbance. Random variation of birth and death rates is more likely to cause a small sub-population to go extinct (Demographic variation).

Meta-Population Dynamics Meta-populations persist or go extinct in a landscape as a function of the balance between: –Extinction Rate: The rate at which sub-populations in patches go extinct. –Migration Rate: The rate at which individuals migrate from one patch to re-colonize empty habitat patches. Extinction Rate > Migration Rate ► Extinction Migration Rate > Extinction Rate ► Persistence

Factors That Influence Extinction Rate Habitat Patch Size Small areas contain limited resources that support only small sub-populations, which are more likely to go extinct. Small areas may include less complex environmental variation. –Less opportunity for niche differentiation –Competitive exclusion (extinction) more likely.

Factors That Influence Extinction Rate Habitat Patch Quality Concentration / availability of resources –Food, Cover, Nest sites Presence of parasites, pathogens, pollutants Low quality (degraded) habitat patches support smaller populations (more likely to go extinct) –Higher mortality and (or) –Lower reproductive success.

Habitat Quality is Influenced by Patch Size and Shape Edge: The border zone within a patch that is influenced by the different environment in the adjacent patch. (Low Quality) –Light, Temperature, Wind, Humidity –Predators, Parasites, Competitors Interior: The central core within a patch where the environment is NOT influenced by surrounding patches. (High Quality)

Patch Size and Edge / Interior Ratio Total Patch Size Area of Edge / Interior Edge Interior X2X2 A = 1 P = 4 (3X) 2 A = 9 P = 12 (5X) 2 A = 25 P = 20

Patch Shape and Edge / Interior Ratio Edge Interior Corridors may be entirely edge environment Circular and Square patches have maximum amount of core interior area for and given amount of patch area

Species Differ In Their Response to Edge Environments Edges can provide diverse food and shelter opportunities in close proximity. Predators and parasites often congregate along edges. Examples: –White-tail deer vs. Moose –Bird Species

Some Bird Species Require Interior Environment Worm-eating warbler Area of Forest Probability of Occurrence Ovenbird Area of Forest Probability of Occurrence Cowbird nest parasites reduce reproductive success of these species near edges.

Some Species Thrive In Edge Environments Gray CatbirdAmerican Robin Area of Forest Probability of Occurrence Area of Forest Probability of Occurrence Species feed in non-forest areas, nest in forest area, and can resist Cowbird nest parasites.

Factors That Influence Migration Rate Spatial proximity: Greater migration rate b/t patches that are near each other, lower migration to isolated patches. Corridors: Connections b/t patches increase migration. Transmissivity of Matrix: Dangerous or impassible matrix decreases migration. Patch Size: Migrating organisms more likely to find a large patch than a small patch (less important than first three factors).

Meta-Population Dynamics (Again) Meta-populations persist or go extinct in a landscape as a function of the balance between: –Extinction Rate: The rate at which sub-populations in patches go extinct. –Migration Rate: The rate at which individuals migrate from one patch to re-colonize empty habitat patches. Extinction Rate > Migration Rate ► Extinction Migration Rate > Extinction Rate ► Persistence

Meta-Population Dynamics Source Areas: Large, high-quality habitat patches w/ self-sustaining sub-populations that produce many migrants. Sink Areas: Small and (or) low-quality habitat patches where sub-populations persist only with continuous immigration from other areas to allow re-colonization after frequent extinction events.

Meta-Population of Bird Species On California Coastal Islands Source Populations Water matrix very hostile to terrestrial bird species Balance b/t extinction & migration rates

Balance of Extinction and Immigration of Bird Species On California Coastal Islands Small Islands Far From the Coast Immigration Rate Less Than Extinction Rate Large Islands Close to the Coast Immigration Rate Greater Than Extinction Rate Source Populations

Balance of Extinction and Immigration of Bird Species On California Coastal Islands Why does this small island far from the coast have such a high immigration rate? Chain of islands provides a “corridor” of stepping stones that facilitates migration.

Balance of Extinction and Immigration of Bird Species On California Coastal Islands Which island do you predict will have the lowest bird species diversity? Small island that is far from the source population w/ no “corridor”. Biggest difference b/t immigration vs extinction rates. Other factors involved?

Balance of Extinction and Immigration of Bird Species On California Coastal Islands Which island do you predict will have the highest bird species diversity? Large island that is close to the source population w/ “corridor”. Biggest difference b/t immigration vs extinction rates. Other factors involved?

Human Impacts On Landscapes and Meta-Populations Habitat Destruction Extinction Habitat Fragmentation –Increasing Edge / Decreasing Interior –Increasing Distances b/t Similar Patches –Hostile (low transmissivity) Human Matrix –Isolation of Sub-Populations

Habitat Fragmentation & Edge: Un-fragmented Habitat Patch Edge Interior

Habitat Fragmentation & Edge: Fragmented Habitat Patch Additional edge due to fragmentation (Interior → Edge)

Habitat Fragmentation & Edge: Fragmented Habitat Patch Fragmentation reduces area of high quality habitat even if total habitat area is the same (but usually isn’t).

Forest Fragmentation in Ohio Landscapes Which landscape provides most high quality forest habitat ? ABC DEF Greatest area of forest Linear patches Less interior area Less forest area Fewer, larger, more blocky forest patches Less edge

Forest Fragmentation in Ohio Landscapes ABC DEF Does landscape B or E provide more / better forest habitat ? Linear patches mainly edge Larger, blocky patches w/ more interior habitat

Forest Fragmentation in Ohio Landscapes ABC DEF Which landscapes facilitate / inhibit migration b/t patches ? Linear patches in closer proximity Blocky patches, widely separated Facilitates migration, but may increase extinction risk. Inhibits migration, but may decrease extinction risk. Small, widely spaced patches Inhibits migration, high extinction risk.

Habitat Fragmentation In a Maryland Landscape Urban areas and roads often hostile to migrating organisms Many forest patches are linear (predominantly edge environment) Habitat Fragmentation Urban Forest Water Open Field

Habitat Fragmentation In a Maryland Landscape Landscape features that facilitate migration ?

Habitat Fragmentation In a Maryland Landscape Landscape features that facilitate migration ? Water drainage channels

Habitat Fragmentation In a Maryland Landscape Landscape features that facilitate migration ? Open fields and hedgerows of abandoned farm lands have high transmissivity that allows animals to move with lower risk of mortality.

The Big Question How can humans manage landscapes to meet human needs while maintaining biodiversity of natural communities ?

The End