Human Resource Use Human Values & Attitudes (Socio-political)

Human Land Use Practices 1) Agriculture2) Suburban Development

Let’s pick on Indiana:

• 97% of land in state = privately-owned

• In central Indiana, • 70+% of land in row crop• <10% in forest• Urban sprawl intensifying

Human Impacts Ecosystem simplification: elimination of

species from food webs via human alterations to land

Example: vertebrate communities in ag. landscapes

Intensive Agriculture&

Clean Farming

Timber Extraction&

Fragmentation

Formation of Terrestrial “Islands”

Oceanic Island = Terrestrial Island ?????

Species-Area Relationship

S = cAz

S = # of species

A = island area

• Positive correlation between island size & number of species

• Applies to terrestrial “islands” also

Island Biogeography

• equilibrium model suggesting that the number of species occurring on an island represents a balance between immigration (in) and extinction (out)

• Robert MacArthur & E.O. Wilson

Habitat Fragmentation • Process of breaking contiguous unit into

smaller pieces; area & distance components

• Leads to:

< remnant patch size

> edge:interior ratios

> patch isolation

< connectivity• Community & Ecosystem processes

altered

Formation of Terrestrial “Islands”

#patches

Patch isolation

Patch size

Edge

What about aquatic systems?

What about aquatic systems?Con.Bio 12(6)

Increased Edge Habitat

Increased Edge Habitat

Habitat Fragmentation • First-Order Effects: fragmentation leads

to change in a species’ abundance and/or distribution

• Higher-Order Effects: fragmentation indirectly leads to change in a species abundance and/or distribution via altered species interactions

Habitat Fragmentation • area-sensitive species: species that

require minimum patch size for daily life requirements

• Edge effects: influence of factors from outside of a patch

Edge Effects • Habitat surrounding a patch can:

- change abiotic conditions; e.g., temp.

- change biotic interactions, e.g., predation

Example of nest predation = edge effect of approximately 50 m into forest patch

But can extend 100’s of meters….maybe km’s

Edge Effects

• How does patch size (in a landscape) & shape affect amount of edge?

• Groups – give me a mathematical example with forested landscapes that have timber extraction via clearcutting

rNdt

dN

K

NrN

dt

dN1

Exponential vs. Logistic

No DDAll populations same

DDAll populations same

No Spatial component

Incorporating Space

Metapopulation: a population of subpopulations linked by dispersal of organisms

• subpopulations separated by unsuitable habitat

• subpopulations differ in population size & distance between

Metapopulation Model

eppcpdt

dp 1

p = habitat patch (subpopulation)c = colonizatione = extinction

Another Population Model

Source-sink Dynamics: grouping of multiple subpopulations, some are sinks & some are sources

Source Population = births > deaths = net exporter

Sink Population = births < deaths

<1

<1

>1

Source-sink Dynamics

Source-sink Dynamics

Corridors

Who Cares?

Why bother discussing these models?

Metapopulations & Source-sink Populatons highlight the importance of:

• habitat & landscape fragmentation

• connectivity between isolated populations

• genetic diversity

Vancouver Island marmot(Marmota vancouverensis)

Isolated from hoary and Olympic marmots

~100 left

Vancouver Island marmot(Marmota vancouverensis)

Natural tree succession

Vancouver Island marmot(Marmota vancouverensis)

• Logging – disjunct patches- max. dispersal = 7 km

• Climate• Prey-Predator Dynamics

Differential Sensitivities to Habitat Alteration

• Niche breadth (diet & habitat) – inverse relation

• Range periphery = more sensitive (W & N)

• Body size = mobility (allometric relation)

• Social and territorial behavior (limited K)

Swihart et al. 2003

Ways to Manage

1) Featured Species Mgt

– single species

– particular purpose

– e.g., white-tailed deer

– could also include “umbrella species” and “flagship species” or “sensitive species”

Ways to Manage2) Species Richness Mgt

– maintain diversity and certain # of each species (follow MVP concept)

3) Indicator Species Mgt

– use a species (or group of species) to monitor environmental conditions

– not necessarily managing for these spp.

– bioindicators, biosentinels, “canary in coal mine”

Ways to Manage

4) Guild Mgt or Life-Form Mgt

– grouping of species based on use of same type of resources (e.g., foraging guilds)