Ecological Restoration (BIO 409) Dr. McEwan Lecture 3: Population Dynamics and Restoration

Ecological Restoration (BIO 409)Dr. McEwan

Lecture 3: Population Dynamics and Restoration

Central Issues in Restoration

Population Viability Analysis.

-Attempt to model population conditions through time, to predict the success or failure of a population.

-Models assume a range of conditions, and the predict success based on those assumptions.

-Modeler can alter the assumptions/alter the conditions to examine the influence of particular environmental or demographic features on population success.

-Most folks recognize that modeling populations in this way is fraught with difficulty because SO much is unknown about SO many species. In fact, many species for which ecological restoration is needed are relatively unknown!

-In application, population modeling IS effective for identifying risks. Maybe most importantly it is used for finding “weak links” in the demographic processes of a given species.

Population Viability Analysis, Cont.

- It is also useful for helping guide initial restoration, particular with choosing which life phase to install (seedings vs. seeds), and for identifying threats to restoration success.

-PVA includes estimates of “uncertainty:” variation arising from random environmental and demographic events.

-Elasticity- is a measure of population growth relative to variation in life-stage transition probabilities. For instance, the probability of transition from one life phase to the next can be manipulated. Populations can also be modeled with population numbers distributed unevenly among life-stages. Population growth is modeled.

-In some instance, long-term demographic instability can be identified based on life-stage distributions.

The Impending Extinction of the Little-winged Pearly Mussel

An ongoing extinction crisis…

• Mussel Diversity Peaks in N. America

• Of 297 known species... 72% are:

– endangered 26% (77)

– threatened 15% (42)

– of “special concern” 24% (72)– or “possibly” extinct 7% (21)

Pegias fabula

Ecology

Filter feedar (Plantivorous) algea etc

Trophic link (Baird 2000), Indicator (Master 1990).

Cool Water, Low Turbidity, Appalachian Streams.

Population/Distribution

• Once Widespread

• Recovery plan (1989) points to six reaches

• Horse Lick Creek, Rockcastle Co.– “last remaining refuge” (DiStefano 1984)

• Little South Fork, Cumberland Riv.– “ The most pristine stream within the entire

known range”

Pegias fabula decline in HLC (J. B. Layzer, Draft)

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10

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1990 1995 1998 1999 2000

Year

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Mussel loss, Little South Fork (Anderson et al. 1991)

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1981 1987

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Methods (PVA)• Big South Fork, Cumberland Rv.

• Assuming 500 individuals

• Modeled 100 populations over 100 years

• Fecundity 10 (Kjos et al. 1997)

Focus on Likelihood of Catastrophe (%)

• 0

• 5

• 10

• 15

• 20

• 25

Pegias fabula decline in response to catastrophe

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100150200250300350400450500

10 20 30 40 50 60 70 80 90 100

Years From Present

Me

an

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lati

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S

ize

0%5%10%15%20%25%

Likelihood of Catastrophe

Results cont.

• At Zero, 500 individuals at present to 109.56• 5% mean population size decreases to a mere 18• 15% the mean population reaches less than one • 25% the mean population reaches less than one

after only 60 years.

Pegias fabula survivorship as a function of catastrophe

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20

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60

80

100

120

0 5 10 15 20 25

# o

f su

rviv

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po

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Likelihood of Catastrophe (%)

Troubled Waters

• In Kentucky, in 1995, there were 31 “fish kill” 172,306 fish

• 963 miles of streams and rivers were “impaired” by coal mining pollution

• Cumberland River, 504 miles were considered to be “not supporting uses” due to pollutants (EQC 1997)

Management Implications

• Continental conservation necessary and yet not sufficient.

• Local efforts must be concerted with regional effort

• Challenges how we value species

Lao Tzu ~500 B.C.Ma-wang-tui manuscript (76)

Though the unhewn log is small,

no one in the world dare subjugate it.

If the feudal lords and kings

could maintain it, the myriad creatures

would submit of themselves.

Fragmentation can fragment populations, leaving them separated in space; however, the populations are interconnected through immigration (gene flow).

“Corridor”

• Gene flow• Source-sink population action• Filtering

SLOSS

Questions:

1)How many individuals to introduce?

2)How large do the patches have to be?

3)What developmental stage to be used?

4)What counts for suitable habitat

5)Dispersal and Colonization

6)Spatial Arrangement of Habitats

7)Sources? Sinks?