Habitat Degradation

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Habitat Degradation Loss
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Species-Area Curves
A very consistent pattern of organismal
distribution
No. species
Area
Data for Galapagos plants from van der Werff
(1983) Vegetatio
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Species-Area Curves
y 30.4 x0.31 R² 0.78
No. species
Log10(y) Log10(30.4 x0.31)
Area
ylog Log10(30.4) (0.31 Log10(x))
Log10 (No. species)
ylog (0.31 xlog) 1.5 R² 0.78
Data for Galapagos plants from van der Werff
(1983) Vegetatio
Log10 (Area)
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Species-Area Curves
Barro Colorado Island
Map from www.stri.org Photo by Christian Ziegler
from www.nytimes.com
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Species-Area Curves
No. species
Area
Log10 (No. species)
Data from the 50-ha Forest Dynamics Plot on
Barro Colorado Island, Panama
Log10 (Area)
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Relative-Abundance Distributions
Whittaker rank-abundance curve
Log10 (No. individuals)
Rank
Most species are rare!
Data from the 50-ha Forest Dynamics Plot on
Barro Colorado Island, Panama
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Seven Forms of Rarity
Most species are rare, but rarity can be defined
in various ways
Habitat specificity
Broad
Restricted
Broad
Restricted
Somewhere large
Local population size
Everywhere small
Wide geographic distribution
Narrow geographic distribution
See Rabinowitz et al. (1986) in Soulé, ed.,
Conservation Biology
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Rare species are especially vulnerable
Small populations are especially prone to
extinction from both deterministic and stochastic
causes
What basic demographic processes can cause a
populations size to change?
Increase birth, immigration
Decrease death, emigration
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Rare species are especially vulnerable
Small populations are especially prone to
extinction from both deterministic and stochastic
causes
In a closed population (i.e., no immigration or
emigration) of size N, the change in population
size for a change in time, whereB births, and
D deaths, is
?N
B - D
?t
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Rare species are especially vulnerable
Small populations are especially prone to
extinction from both deterministic and stochastic
causes
In a closed population (i.e., no immigration or
emigration) of size N, the change in population
size for a change in time, where b per capita
birth rate, and d per capita death rate, is
?N
b(N) d(N)
?t
?N
(b-d)(N)
?t
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Rare species are especially vulnerable
Small populations are especially prone to
extinction from both deterministic and stochastic
causes
Substitute r for (b-d), where r per capita
growth rate
?N
r(N)
?t
If rgt0, N grows if rlt0, N declines if
r0, N does not change
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Rare species are especially vulnerable
Small populations are especially prone to
extinction from both deterministic and stochastic
causes
Example, r 0.5 Population A
Population B NA,t 1000
NB,t 10
?N
Nt1 Nt
?t
NA,t1 500
NB,t1 5
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Rare species are especially vulnerable
Small populations are especially prone to
extinction from both deterministic and stochastic
causes
Deterministic ? r lt 0
Genetic stochasticity Demographic stochasticity
? individual variability of r Environmental
stochasticity ? temporal fluctuations of
r Catastrophes
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Habitat Destruction, Loss, Degradation
At least 83 of the Earths land surface has been
transformed by human activities (Sanderson et
al. 2002)
About 60 of Earths ecosystems are considered
degraded or unsustainably used (Millennium
Ecosystem Assessment 2005)
98 of U.S. streams and rivers have been
fragmented (see next lecture) by dams(Benke
1990)
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Habitat Destruction, Loss, Degradation
Habitat degradation impacts that affect many,
but not all species some of which may be
temporary
Habitat destruction loss impacts that affect
nearly all species time scale for recovery is
very long
How do humans destroy and degrade habitats and
ecosystems? E.g., agricultural activities,
extraction activities, certain kinds of
development
These are often considered to be the most
important threats to biodiversity, since they
eliminate species, reduce population sizes, and
reduce performance of individuals
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Habitat Destruction, Loss, Degradation
Loss of forest habitat in Borneo
Image of shrinking forest cover on Borneo from
www.planttreesaveplanet.com
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Habitat Destruction, Loss, Degradation
Loss of terrestrial coastal habitats in Louisiana
Image of Louisiana land loss (1932 - 2050) from
www.lacoast.gov
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Habitat Destruction, Loss, Degradation
Anthropogenic degradation of oceans
Halpern et al. (2008) Science see
www.nceas.ucsb.edu
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Habitat Destruction, Loss, Degradation
Loss of ice from polar ice cap
1979
2003
Minimum sea ice concentration 9 decline per
decade
Images from www.nasa.gov
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Pollution is a Form of Habitat Degradation
Light pollution Air pollution acid rain Solid
waste plastics Chemical pollution (e.g., DDT,
endocrine disruptors)
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Pollution is a Form of Habitat Degradation
Rachel Carson(1907 1964)
Silent Spring (1962) motivated creation of the
U.S. Environmental Protection Agency
Photo from Wikipedia
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Pollution is a Form of Habitat Degradation
Theo Colborn(b. 1927)
Theo Colborn, Dianne Dumanoski John P. Meyers
(1997) Our Stolen Future How We Are Threatening
Our Fertility, Intelligence and Survival
Image from www.time.com
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Pollution is a Form of Habitat Degradation
Light pollution Air pollution acid rain Solid
waste plastics Chemical pollution (e.g., DDT,
endocrine disruptors) Excessive nitrogen
inputs Eutrophication
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Pollution is a Form of Habitat Degradation
Excessive nitrogen inputs eutrophication
Image from www.gulfhypoxia.net
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Pollution is a Form of Habitat Degradation
Excessive nitrogen inputs eutrophication result
in coastal hypoxia (i.e., the dead zone
phenomenon) every summer off Louisianas coast
Image from www.lacoast.gov
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Biodiversity Hotspots Usually defined by species
richness, endemism threats
Map from www.fao.org