Transcript Slide 1

Habitat Degradation & Loss
Species-Area Curves
500
No. species
A very consistent pattern of
organismal distribution
400
300
200
100
0
0
Data for Galapagos plants from
van der Werff (1983) Vegetatio
Area
2500
5000
Species-Area Curves
Log10(y) = Log10(30.4 •
x0.31)
500
No. species
y = 30.4 • x0.31
R² = 0.78
Data for Galapagos plants from
van der Werff (1983) Vegetatio
300
200
100
0
Log10(y) = Log10(30.4) +
(0.31 • Log10(x))
0
Log10 (No. species)
ylog = (0.31 • xlog) + 1.5
R² = 0.78
400
2500
Area
5000
3
2.5
2
1.5
1
0.5
0
-1
0
1
Log10 (Area)
2
3
4
Species-Area Curves
Barro Colorado Island
Map from www.stri.org; Photo by Christian Ziegler from www.nytimes.com
Species-Area Curves
No. species
400
300
200
100
0
Log10 (No. species)
0
Area 10
20
30
3
2.5
2
1.5
1
0.5
0
Data from the 50-ha Forest Dynamics
Plot on Barro Colorado Island, Panama
-2.5 Log
10
(Area)-0.5
1.5
Relative-Abundance Distributions
Whittaker rank-abundance curve
Log10 (No. individuals)
5
4
3
2
1
0
0
100
200
300
Rank
Data from the 50-ha Forest Dynamics
Plot on Barro Colorado Island, Panama
Most species are rare!
400
Seven Forms of Rarity
Most species are rare, but rarity can be defined in various ways
Habitat specificity
Local
population
size
Broad
Restricted
Broad
Restricted
Somewhere
large
Common
Rare
Rare
Rare
Everywhere
small
Rare
Rare
Rare
Rare
(no examples?)
Wide
Narrow
Geographic distribution
See: Rabinowitz et al. (1986) in Soulé, ed., Conservation Biology – based on British flora
Rare species are especially vulnerable
Small populations are especially prone to extinction
from both deterministic and stochastic causes
Image of extinct Hawai’i ’Ō’ō (Moho nobilis) from Wikipedia
Rare species are especially vulnerable
Small populations are especially prone to extinction
from both deterministic and stochastic causes
E.g., Hawaii’s
native bird species
Half went extinct
soon after the
Polynesians arrived
(in ~ 300 A.D. / C.E.)
Image of extinct Hawai’i ’Ō’ō (Moho nobilis) from Wikipedia
Half of the
remaining species
went extinct soon
after Captain James
Cook arrived
(in 1778)
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 = births, and D = deaths, is:
∆N
∆t
=B-D
Remember the “BIDE factors”: birth, immigration, death & emigration
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
∆t
∆N
∆t
= b(N) – d(N)
= (b-d)(N)
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
∆t
If r>0, N grows;
= r(N)
if r<0, N declines;
if r=0, N does not change
Rare species are especially vulnerable
Small populations are especially prone to extinction
from both deterministic and stochastic causes
Example, r = –0.5 :
Population A
NA,t = 1000
Nt+1 = Nt +
NA,t+1 = 500
Population B
NB,t = 10
∆N
∆t
NB,t+1 = 5
Rare species are especially vulnerable
Small populations are especially prone to extinction
from both deterministic and stochastic causes
Deterministic  r < 0
Genetic stochasticity
Demographic stochasticity  individual variability of r
(e.g., variance)
Environmental stochasticity  temporal fluctuations of r
(e.g., change in mean)
Catastrophes
Demographic & Environmental Stochasticity
Demographic Stochasticity
Each student is a sexually reproducing, hermaphroditic,
out-crossing annual plant.
Arrange the plants into small sub-populations (2-3 plants/pop.).
In the first growing season (generation), each plant mates
(if there is at least 1 other individual in the population)
and produces 2 offspring.
Offspring have a 50% chance of surviving to the next season.
flip a coin for each offspring;
“head” = lives, “tail” = dies.
Note that average r = 0; each parent adds 2 births to the population and on
average subtracts 2 deaths [self & 1 offspring – since 50% of offspring live and
50% die] prior to the next generation.
Habitat Destruction, Loss, Degradation…
At least 83% of the Earth’s land surface has been
transformed by human activities
(Sanderson et al. 2002)
About 60% of Earth’s 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)
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 & degrade habitats & ecosystems?
E.g., agricultural activities, extraction activities,
certain kinds of development
These are often considered to be the most important direct threats to
biodiversity, since they eliminate species, reduce population sizes,
and reduce performance of individuals
Habitat Destruction, Loss, Degradation…
Loss of terrestrial coastal habitats in Louisiana
Image of Louisiana land loss (historical & projected;1932 - 2050) from www.lacoast.gov
Habitat Destruction, Loss, Degradation…
Degradation of marine and coastal habitats in Louisiana
Deepwater Horizon – drilling rig explosion on April 20, 2010
Map from www.npr.org
Habitat Destruction, Loss, Degradation…
Anthropogenic degradation of oceans
Halpern et al. (2008) Science; see www.nceas.ucsb.edu
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
Pollution is a Form of Habitat Degradation
Light pollution
Air pollution & acid rain
Solid waste & plastics
Chemical pollution (e.g., DDT, endocrine disruptors)
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
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
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
Etc…
Pollution is a Form of Habitat Degradation
Excessive nitrogen inputs & eutrophication
Image from www.gulfhypoxia.net
Pollution is a Form of Habitat Degradation
Excessive nitrogen inputs & eutrophication
contribute to coastal hypoxia (i.e., the “dead zone” phenomenon)
every summer off Louisiana’s coast
Image from www.lacoast.gov
Biodiversity Hotspots
Usually defined by species richness, endemism & threats
These hotspots of biodiversity cover only ~1.5% of the Earth’s land;
if they were destroyed ~1/3 of Earth’s species would go extinct
Figure from Myers et al. (2000, Nature)
Biodiversity Hotspots
Usually defined by species richness, endemism & threats
Map from www.fao.org
Biodiversity Crisis
Whether or not habitat degradation or loss occurs in a biodiversity hotspot, any
resulting biodiversity losses contribute to the global phenomenon, since
local losses aggregate to produce the global crisis.
Image of oiled pelicans on June 3, 2010 from the Gulf of Mexico from Wikipedia